Keithley 148 Service manual

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Kelthley~in&&nts, Inc. ~&arrantSth~s product to befree from defects

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;S~~~EM~E,N~T~OF~CAL1BRATION

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~Nationat ~Bureau of Standards through equipment which is cal~@reted at ~Nationat ~Bureau of Standards through equipment which is cal~@reted at

,~ fWrned ~Jnterv& by comparisqn to ,~ertlfii Standards maintained in

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the Laboratories of :Keithley lnstruments;~ Inc. the Laboratories of :Keithley Instruments;~ Inc.

INSTRUCTION MANUAL

Model 148

Nanovoltmeter

DOCUMENT #29029

CONTENTS

MOOEI, 148

ILlsJSTRATIONS

ILLUSTRATIONS

FIG. TITLE PACE

la Front Panel ................................

lb Front Panel With Model 1481 Input Cable 2

Front Panel Conrrole. ...........................

3 Rear Panel Conerols and Connections

4

Model 1481 Low-Thermal Input Cable. 5 Made! 1483 Low-Thermal Connection Kit 6 Normal Wave Form at Demodulator with Input Sbor’ted. 7 Wave Format Demodulator Sham with Some Pickup.

8

Wave Format Demodulator when Amplifier is Saturated

9 “sing Model 148 with 4-Terminal Connections 10 Exploded “few far Rack Mounting 11 Block Diagram of Model 148 Amplifier Circuits 12 13 Block Diagram of Model 148 Power Supplies 14 Model 148 Input Compartment 15 Correct Wave Form in dc-to-dc Inverter. 16 correct wave Form at Point F in Oscillator circuit. 17 Improper wave Form af point F in Oscillator Circuit 18 NOf Used.

19 Nof Used. .................................

20 Top View of Model 148 massis 21 Bottom View of Model 148 Chassis. 22 Transistor Locations on Printed Circuit 76. 23 Capacitor and Diode Locations on Printed Circuit 76 24 25 Resistor and Test Point Locations on Printed Circuit 76

26 27 Component Locations on Printed Circ”it 74, Top Face 28 Resistor and Test Point Locationa on Printed Circuit 75 29 Capacitor and Transistor Locations on Printed Circuit 75.

30 31 Resistor LOcationS on RANOE SWitCh (5102)

Model 148 Input Circuit

.................................

Resistor Locations on Printed Circuit 76. Resistor and Test Point Locations on Printed Circuit 74. Bottom Face.

Resistor Locations on RANGE Switch (S102)

.......................... 20

...................... 18

........................ 26

....................... 38

.................. 3

.................... 6

.................... 10

............ : ...... 10

............ 15

.............. 15

............ IS

................ 17

............... 19

................. 23

.................. 31

............ 32

..................... 39

................ 40

............ 40

................. 41

............ 42

................. 44

--

.......... 41

.......... 4,

.........

... 42

43

1 4

0375

SPECIFICATIONS

MODEL 148

SPECIFICATIONS

iv

0375

MODEL 148

GENERAL DESCRIPTION

SECTION 1.

GENERAL DESCRIPTION

l-l. GENERAL.

The Keithley Model 148 Nanovoltmeter conveniently measures dc potentials

a.

from 10 nanovolts (10 x 10-g

volts) to 100 millivolts full scale. It makes accurate and sensitive measurements without painstaking methods often previously required.

Meter accuracy is 2% of full scale on all ranges. than 1 nanovolt peak-to-peak on the lo-nanovolt range. than 10 nanovolts per 24 hours after warm-up.

On the three most sensitive

Zero drift is less

Noise is less

ranges, line-frequency rejection is greater than 1OOO:l.

For reliable and versatile use,

b.

design, except for the first two input stages.

the Nanovoltmeter is of solid-state

It has high line isolation

and battery or line operation.

0972

FIGURE la. Front panel.

GENERAL DESCRIPTION

MODEL 148

1-2.

ing many grounding problems.

FEATURES. Battery operation permits complete isolation from power line, eliminat-

a.

Battery operation also allows flexibility and

convenience in use. The Model 148 automatically recharges the battery if

needed when the ac power cord is connected.

The Nanovoltmeter has a 21 volt at 1 milliampere output at full-scale

b.

meter deflections for driving a recorder or oscilloscope.

Accuracy is 1% of

full scale for output.

c. A zero suppression circuit permits measuring small changes in a larger

dc signal.

l-3. APPLICATIONS.

The Model 148 Nanovoltmeter measures very small dc potentials or

a. small changes in dc potentials from low impedance sources. These are found in fundamental or applied research, laboratory standards work, cryogenic

experiments and instrument development for space research.

It can also

serve as an amplifier in these uses.

Typics.1 uses include measuring small temperature differences and

b.

small temperature changes indicated by thermocouple outputs, small changes

in conductance,

outputs used in narrowband spectrum analysis. the thermoelectric power of metals,

making Bolometer

super conductivity in the lo-6 ohm range, and thermopile

Other uses are determining

conducting Hall effect studies, and

measurements.

Also, the Model 148 is suited for use with potentiometers, ratio sets and resistance bridges, including Wenner, Wheatst and Kelvin Double bridges. It can be used to make 4-terminal resistance

measurements.

2

0972

MODEL 148 GENERAL DESCRIPTION

0972

FIGURE lb.

Front Panel With Model 1481 Input Cable.

3

GENERAL DESCRIPTION

ZERO s”PPmssIoN

POWER

SWITCH

5201 COARSE 5103

MODEL 148

*

FINE R168

4

FIGURE 2. Front Panel Controls.

0972

MODEL 148 NANOVOLTMETER

OPERATION

SECTION 2.

.2-l. FRONT PANEL CONTROLS.

a. AC CONNECTED Lamp.

The Lamp is lit whenever the unit is connected to

(See Figure 2.)

OPERATION

the ac line and the POWER SUPPLY Switch is in the AC or OFF position.

NOTE

The AC CONNECTED Lamp indicates only that the instrument is connected to the ac power line; it does not indicate that the Nanovoltmeter is operating.

Also, when the POWER SUPPLY Switch is turned from AC to OFF, a difference in Lamp brightness is normal.

BATTERY CHARGING Lamp. When lit,

b.

charging.

not lit,

POWER SUPPLY Switch.

c.

The charge current determines its brightness.

then the battery is charged.

The Switch controls the mode of operation for

this Lamp indicates the battery is

If the lamp is

the power supply.

AC position:

1.

The battery will be charged if needed; then,

The Nanovoltmeter will operate from the ac power lint.

the BATTERY CHARGING Lamp

will light.

OFF position: The Model 148 is not operating.

2.

will be charged,

BATTERY position:

3.

if needed and if the power cord is connected.

The Nanovoltmeter is operated from its battery.

The ac power line is internally disconnected;

However )

the AC CONNECTED Lamp is off;

tk! battery

the battery cannot be charged.

BATT.TEST position:

4.

When the POWER SUPPLY Switch is held in this

position, the Model 148 shows the state of the battery charge directly

on its meter. All circuits within the instrument are the same as for

battery operation except at the meter terminals.

Switch Settin

TABLE 1.

Indicating Lamps and POWER SUPPLY Switch Settings.

The table shows the relationship between the front panel

lamps,

the power cord and the POWER SUPPLY Switch setting.

OPERATION

MODEL 148 NANOVOLTKETER

RANGE Switch.

d.

The RANGE Switch selects the full-scale meter sensitivity

(either microvolts or millivolts) for one of nine ranges, from 0.01 to 100.

FUNCTION Switch.

e.

The FUNCTION Switch selects the function - MICROVOLTS

or MILLIVOLTS - which is to be measured.

ZERO SUPPRESS Controls.

f.

The COARSE Control disconnects the suppression circuit (in OFF position)

1.

or selects one of four suppression voltages in decade steps.

The FINE Control is a continuously variable adjustment for the suppression

2.

voltage set by the COARSE Control.

Two controls determine the amount of zero suppression.

Refer to Table 3.

It adjusts the range between the positive

and negative values of the maximum voltage set by the COARSE Control.

INPUT Receptacle.

g.

The INPUT Receptacle is of a special low-thermal design.

Use only the Models 1481, 1482 and 1486 for mating connectors.

5103:

FIGURE 3. Model 148 Rear Panel Controls and Connections. refer to Replaceable Parts List and schematic diagrams.

2-2.

REAR PANEL CONTROLS AND CONNECTIONS.

Line Voltage Switch. The screwdriver-operated slide switch sets the

a.

Model 148 for 117 or 234~volt ac power lines.

Fuse.

b.

For 117~volt operation,

1. For 234volt operation, use only a MDL Slow-Blow l/16-ampere fuse.

2.

Power Cord. The 3-wire power cord with the NEMA approved 3-prong plug

c.

provides a ground connection for the cabinet.

use a 3 AG or MDL Slow-Blow l/8-ampere fuse.

An adapter for operation from

2-terminal outlets is provided.

WER

RD

Circuit designations

6

0464

MODEL 148 NANOVOLTMETER

A note above the power cord shows the ac power line frequency

for which the rejection filter is adjusted.

will work at any line frequency from 50 to 1000 cps, but ac

rejection is best at the indicated frequency.

OPERATION

The instrument

DEMODULATOR TEST.

d.

A phone jack provides access to the demodulator for

test purposes.

e.

OUTPUT.

The OUTPUT Receptacle provides fl volt at one milliampere for

a full-scale meter deflection on any range.

GND and LO Terminals. The ground terminal (GND) is connected to the chassis

f. and the third wire of the power cord. The low terminal is connected to circuit ground and the low side of the input connection.

2-3.

or from its battery. For most uses,

operation, however,

problems.

MODE OF OPERATION. The Model 148 operates either from an ac power line

it functions well from ac. Use battery

if the ac power line will create ground loop or isolation

Isolation from low to ground is complete for battery operation when the power cord is disconnected; it is greater than 10' ohms with the power cord connected. Also use battery operation to reduce the 8-cps ripple which may appear at the output with the input shorted in ac operation.

See

paragraph Z-13.

NOTE

Before using the battery operation, thoroughly read paragraph 2-4.

Inproper to

inaccurate

battery

measurements.

operation can damage the

battery

pack and lead

2-4. BATTERY OPERATION.

The Model 148 is supplied w;th a rechargeable 6-volt, 4 ampere-hour

a.

nickel-cadmium battery pack. Re<,c~mmended:

than eight consecutive hours without recharging.

rate /

the battery should last about 1000 recharge cycles.

Do not use the battery more

At this discharge

NOTE

Permanent damage to the battery pack occurs if it is used

for more than 14 consecutive hours without recharging.

At this discharge rate, the recharge cycles are greatly

reduced.

Before using the Model 148, check the state

of the battery charge.

Check the battery charge before making a measurement. Hold the

b.

POWER SUPPLY Switch in the BATT. TEST position.

The minimum acceptable charge is a meter indication of +8; full charge is shown by the BATTERY CHARGING Lamp not being lit.

Recharge if needed. Otherwise, battery operation is the same as for the ac power line operating mode; refer to paragraph 2-5.

1067'

7

OPERATION

MODEL 148 NANOVOLTMETER

NOTE

When the battery is used beyond its capacity, two effects are seen.

There is a shift in zero offset from ac to battery operation. Also, the power supplies do not regulate and high ripple voltages appear at the supply outputs.

(See paragraph 4-7.)

To recharge the battery,

c.

come-t the power cord to an ac power line.

the POWER SUPPLY Switch to AC or OFF.

The BATTERY CHARGING lamp will light. The

Turn

battery will be charged only if needed, and the circuit automatically prevents it from being overcharged.

It is suggested that the battery be used during the day and be recharged

d.

at night.

Leave the instrument always connected to the ac power line; then turn the POWER SUPPLY Switch to OFF at night, After a fully charged battery is used for eight consecutive hours, it will recharge within 14 hours. the power cord connected has little effect on the isolation:

109 ohms with

Leaving the POWER SUPPLY Switch in BATTERY position and the low-ground link disconnected. 2-5. OPERATING PROCEDURES,

Set the front panel controls as follows:

a.

POWER SUPPLY Switch OFF FUNCTION Switch MILLIVOLTS RANGE Switch 100 ZERO SUPPRESS COARSE Control OFF

NOTE

Make sure the ZERO SUPPRESS COARSE Control is OFF. If it is not, a suppression voltage is introduced, causing an error in measurements.

Connect the unknown voltage source to the INPUT Receptacle.

b.

Refer to

paragraph 2-6 for suggestions.

Check the voltage shown on the rear panel Line Voltage Switch; connect the

c.

Model 148 to the ac power line. Make sure the frequency shown above the power

cord is the frequency of the ac power line. At this point, the AC CONNECTED Lamp

will light, as will the BATTERY CHARGING Lamp if the battery is being charged. If

the circuit low is to be at ground, put the low-ground link between the LO and GND terminals on the rear panel.

Turn the POWER SUPPLY Switch to the desired mode of operation, AC or BATTERY.

d.

Increase the sensitivity of the Model 148 until the

e.

meter

shows the greatest

on-scale deflection.

Check the source resistance to make sure it is within the maximum value

1. specified for the range being used. (See Table 2.) If the maximum resistance is exceeded, the Model 148 may not be within its specifications.

1067

MODEL 148 NANOVOLTMETER OPERATION

Zero offsets with the Zero Suppress Controls off will vary with the

2. quality of the circuit's thermal construction. See paragraph 2-14. a Model 1486 with a copper-wire short is on the Model 148 INPUT Receptacle, offset should be less than 0.2 microvolt.

Shifts in source resistance also affect the zero offset, if the

3. source resistance approaches the maximum value given in Table 2. effect is negligible for source resistances less than 10% of the

maxiwm value.

If the input is left completely open-circuit, the meter will drift

4.

off scale on any range.

Refer to Table 4 if problems exist during the measurement.

5.

Minimum

Input Resistance Maximum Source Line Frequent

Range Greater Than Resistance Rejection

when

This

0.01 microvolt

0.03 microvolt

0.1 microvolt

0.3 microvolt

1 microvolt

3 microvolts .O microvolts 300 kll i0 microvolts 300 kn 10 microvolts 300 krl

0.01 millivolt

0.03 millivolt

0.1 millivolt

0.3 millivolt 1 millivolt

3 millivolts .O millivolts IO millivolts 10 millivolts

TABLE 2. Model 148 Input Resistance, Maximum Source Resistance, and Minimum Line Frequency Rejection by Range. the ratio of impressed peak-to-peak line frequency (50 or 60 cps)

voltage at input to the indicated dc voltage.

1 kcl 3 kcl 30 n

10 kn

30 kn

100 lcrl 300 kn 3 kc1

1 I%,2 1lQ l?Sl 10 kn 1 Ma. 1Kl 3Kl 5 Ml 5 I%1 5 Nl

10 n

100 n 300 11

1 lu? 3 kn

3&l 3kn

10 kn 10 kcl

10 kn

10 kn 30 m 50 Icn

50 k!J 5:l 50 kn

The rejection is

3OOO:l 1OOO:l 1OOO:l

5OO:l 5OO:l 1OO:l

decreasing

to 5O:l

100: 1

5O:l 2O:l 2O:l 2O:l 1O:l

1O:l

5:l

Three millivolt and microvolt ranges overlap: 0.01, 0.03 and 0.1

f.

millivolts and 10, 30 and 100 microvolts.

source resistance is high or if large 60-cps fields are present.

volt ranges are more convenient to use if subsequent measurements require more

sensitive ranges. frequency rejection by range.

At low levels,

g.

between the input leads and the circuit under test.

leave the instrument connected, and adjust the zero after establishing

a zero reference in the apparatus under test.

1067

Refer to Table 2 for maximum source resistance and line

spurious emf's may be generated simply by contact

use the millivolt ranges when the

The micro-

If possible, always

For example,

in bridge measurements,

9

MODEL 148 NANOVOLTMETER

disconnect the bridge exciting voltage; or with a phototube, shield the tube from light.

2-6. ACCESSORIES FOR INPUT CONNECTIONS.

a. The easiest way to connect the

voltage source to the Model 148 input

is with the Model 1481 Low-Thermal

Input Cable supplied with the instru-

ment.

Use the Cable for temporary

setups, for measurements at several points, and when fast connections are needed. The Model 1481 connects directly to the INPUT Receptacle.

I

FIGURF: 4.

Model 1481 Low-Thermal

Input Cable.

possible or where very low thermal

Where more permanent setups are

b.

connections are needed, use the Model

1482 Low-Thermal Input Cable. It is similar to the Model 1481, except it

has bare copper leads instead of alligator clips.

Clean the bare wire with

a non-metallic abrasive, such as Scotch Brite or its equivalent, before making

the connection. Crimp connections to the voltage source, as possible with the Model 1483 Kit, provide the best low-thermal connections.

If cadmium solder is used for a connection, make sure the soldering

C.

iron used is clean and that it has not been used with regular solder before.

Use only rosin solder flux.

If possible, heat sink all cadmium-soldered

joints together to reduce generated thermal emf's.

Use crimp connections with copper

d.

wire and lugs for the best low-thermal

joints.

The Model 1483 Low-Thermal Connection Kit contains a crimp tool, shielded cable, an assortment of copper

lugs,

copper wire, cadmium solder and nylon bolts and nuts. It is a complete kit for making very low-thermal measur-

ing circuits. The Kit enables the user of the Model 148 to maintain the high

thermal stability of the Nanovoltmeter

in his own circuit.

The Model 1486 male low-thermal

e.

input connector is for connecting custommade circuits to the Model 148. It also makes a good low-thermal shorting plug

for testing the Nanovoltmeter: crimp a

short length of pure copper No. 18 or

'IGURE 5. Model 1483 Low-Thermal

Connection Kit.

No. 20 wire between the two pins of

the connector.

Other available accessories are:

f.

contains replacement parts for the Model 1483.

The Model 1484 Refill Kit, which

The Model 1485 female low-

thermal input connector to use with the Model 1481, 1482 or 1486 for building

shielded low-thermal circuits.

10

0464.

MODEL 148 NANOVOLTMETER

2-7. ZERO SUPPRESS OPERATION.

OPERATION

Purpose:

a.

order to use a more sensitive range to observe a superimposed signal.

100 times full scale may be suppressed on the ranges from 0.1 millivolt to

0.01 microvolt. For example, the Model 148 can measure changes of less than one microvolt in a lOO-microvolt steady signal on its l-microvolt range.

Suupression Voltaxes Available: The COARSE Control sets the suppression

b.

voltage to one of eight values, depending upon its setting and the FUNCTION

Switch setting. (Refer to Table 3.) The FINE Control continuously adjusts the voltage between tile positive and negative value of COARSE Control setting.

For example, if the COARSE Control is at 1 for a suppression voltage of

0.24 millivolt, +0.24 mv.

FUNCTION Switch

Setting

MICROVOLTS

MICROVOLTS MICROVOLTS MICROVOLTS

MILLIVOLTS 1 0.24 millivolt MILLIVOLTS 2 1.2 millivolts MILLIVOLTS 3 12 millivolts

MILLIVOLTS 4 120 millivolts

The zero suppression circuit cancels any constant voltage in

up to

the FINE Control adjustment span is from -0.24 mv to 0 to

Maximum

ZERO SUPPRESS COARSE

Control Setting

1 2 3 4

Suppression

Voltage

0.24 microvolt

1.2 microvolt6

12 microvolt6

120 microvolt6

TABLE 3.

voltage shown is the maximum value, ?15%, for each FUNCTION Switch and

COARSE Control setting.

c. Operation,

Keep the COARSE Control in OFF position.

1.

Switches for the most sensitive meter reading.

Completely turn the FINE Control in the direction opposite to the meter

2.

deflection (counterclockwise for positive deflections and clockwise for negative deflections).

Increase the COARSE Control setting until the meter needle passes

3.

through zero.

Set the RANGE Switch to a more sensitive range, up to 100 times more

4. sensitive than the original range (four RANGE Switch positions). the FINE Control to zero, if necessary.

Suppression Voltage by Control Settings. The zero suppression

Adjust the RANGE and FUNCTION

Adjust the FINE Control for zero deflection.

Readjust

0365

11

OPERATION

MODEL 148 NANOVOLTMETER

NOTE

On the highest zero suppression range - 120 millivolts maximum - a zero offset will be apparent when changing the RANGE Switch settings. On this zero suppres-

sion range, first set the RANGE Switch to the range intended to be used. Then zero the meter with the ZERO SUPPRESS FINE Control. This offset is introduced

only when the ZERO SUPPRESS COARSE Control is set to 4 and the FUNCTION Switch

is set to MILLIVOLTS. There is no significant offset on any other zero supprss-

sion range.

2-8. DIFFERENTIAL MEASUREMENTS.

The Model 148 will measure the difference between two voltages, neither or which is

a.

at power line ground. It can be floated up to 1-400 volts off ground in ac operatior

the Model 148 is battery operated it is completely isolated from line.

Unplug the Model 148 power co? and use battery operation before measuring a source which is more than f400 volts instantaneous off ground.

Damage to the

instrument can result if the power line is connected under these conditions.

When

CAUTION

The front panel controls are electrically connected to the case.

"cord is unplugged,

Use necessary safety precautions.

For best results in making differential measurements, follow the steps below:

b.

Remove the link from the LO or GND terminal on the rear panel.

1. Connect the voltage source to the Nanovoltmeter i,L,wt.

2.

scribed in paragraph 2-5.

urements.

Do not ground any recorders used with this operation, since the low of the

the case may be at a voltage equal to the off-ground voltage.

Make measurements as de-

The zero suppress controls may be used for differential meas-

If the power

Model 148 output is no longer grounded.

3. If power line frequency pickup is a problem, battery operation usually provides

better results.

2-9. RECORDER OUTPUT. on any range is *l volt at one milliampere.

tance is less than 5 ohms within the amplifier pass band.

ac and battery operation.

The output of the Nanovoltmeter for a full-scale meter deflection

Accuracy is 1% of full scale. Output resis-

Output may be used during both

If the Model 148 is used for differential meas?xements, do not

ground the recorder connected to the output.

When recording the Keithley Model 370 Recorder offers complete compatibility with

a.

the Model 148. The output is sufficient to drive the Model 370 without the use of any re-

corder preamplifiers. The Model 370 allows maximum capability of the Model 148.

1% linearity, 10 chart speeds and can float up to *500 volts off ground.

Using the Model

It has

370 with the Model 148 avoids interface problems which may be encountered between a meas-

uring instrument and a recorder.

The Model 370 is very easy to use with the Model 148. All that is necessary is con-

b.

necting the two units and adjusting an easily accessible control for full-scale recorder

12

1067

MODEL 148 NANOVOLTMETER

OPERATION

L

Trouble (seen on meter)

Change in offset between ac

Possible Cause

Low Battery

Refer to

paragraph 2-4

and battery operation Very slow response time

High source resistance paragraph 2-12

Improper shielding paragraph 2-13

Excessive drift

I I

Thermal emfs

paragraph 2-14

I

Improper connection to input paragraph 2-15

Excessive noise or needle

instability

High source resistance paragraphs 2-11,2-l improper shielding paragraph 2-13 Improper connection to input

paragraph 2-15

Thermal emfs paragraph 2-14

Excessive temperature sensitivity Thermal emfs

paragraph 2-14

presence of large, constant zero suppress Controls on paragraph 2-5 signal Thermal emfs paragraph 2-14

Improper connection to input paragraph 2-15

Excessive 8-cps beat at output

or meter magnetic shielding

I

TABLE 4.

Troubleshooting Operating Procedures. *he Table gives some possible sources of

Improper location or poor

I

paragraph 2-13

I

errors while using the Model 148 and refers to instructions to correct the situation.

deflection. The furnished Model 3701 Input Cable mates with the output connector on the

Model 148. On the most sensitive ranges of the Model 148, under some conditions, a" 8-

cps beat may appear. This condition can be eliminated by mounting a 100~microfarad capac-

itor across pins 14 and 17 in the back of the Model 370 Recorder.

2-10.

ACCURACY CONSIDERATIONS.

For sensitive measurements - 10 millivolts and below -

other considerations beside the voltmeter affect accuracy. The Model 148 reads only the

signal received at its input; therefore, it is important that this signal be properly transmitted from trle source. The following paragraphs indicate factors which affect ac-

CllrWy: thermal noise, loading, shielding, thermal emfs and circuit connections.

Table

4 also offers a quick reference to correct troubles which may occur. 2-11 THERMAL NOISE.

The lower limit in measuring small potentials occurs when the Johnson noise, or

a. thermal agitation, becomes evident. The amount of noise present in the source is show" in the following equations.

1. The thermal noise in any ideal resistance can be determined from the Johnson noise,

equation:

-As

=4kTRF Eq. 1

where Er,, is the rms noise voltage developed across the voltage source;

T is the temperature in degrees Kelvin;

1067

13

OPERATION MODEL 148 NANOVOI~'~ETEl?

R is the source resistance in ohms; F is the amplifier bandwidth in cps; k is the Boltzmann constant (1.38 x lo-23 joules/OK).

For an ideal resistance at room temperature (300°K), equation 1 simplifies to

rms = 1.29 x lo-lo (R F)112

Peak-to-peak meter indications are of more interest than the rms value.

2.

mentally,

E

the peak-to-peak Johnson noise is about five times the rms value.

Eq. 2

Experi-

At room

temperature, equation 2 becomes

= 6.45 x lo-10 (R F)li2

EPP

Eq. 3

where Epp is the peak-to-peak noise voltage developed across the voltage source.

The Model 148 bandwidth, F,

3.

can be estimated from the response speed, tr, by:

F = 0.35/tr Eq. 4

The response speed varies with the range used and the source resistance.

On the O.l-

microvolt range when the source resistance is less than 10 ohms, for example, the bandwidth is greater that 0.7-cps.

The maximum specified response speed for this situation

is 0.5 second, so the 0.7-cps bandwidth is a minimum value.

As an example, determine the Johnson noise of a lo-ohm ideal resistor. Measured

4-

with the Model 148 on the 0.1~microvolt range and using equation 3, this becomes

17.1 x lo-10 volts peak-to-peak or 1.71 nanovolts peak-to-peak minimum. In general, good wirewound or low-noise metal-film resistors approximate ideal resis-

b.

tors,

and equations 2 and 3 are nearly correct. If the source resistance is.composed of

other materials, it may be necessary to include other terms in the equations to account for flicker, l/f, and current noise over and above the thermal noise.

c. As seen in equations 2 and 3, ficant in the microvolt region. fore, keep the source resistance as low as possible.

the noise of even low resistance values becomes signi-

The noise in non-ideal resistors is even greater. There-

Other effects of high source resis-

tances are decreased response speed and added pickup of extraneous voltages.

2-12. INPUT RESISTANCE.

is obtained by using high feedback factors.

The Model 148 is a feedback amplifier, and its input resistance

When the source resistance exceeds its physi-

cal input resistance - the amplifier without feedback - the feedback is partially de-

stroyed.

higher resistances may be used, but noise, offset,

result.

Normally, do not exceed the maximum source resistance specified in Table 2;

slow response time and instability may

On the most sensitive ranges,

the maximum source resistance is consistent with

Johnson noise considerations. Z-13. SHIELDING.

Due to its narrow bandwidth, the Model 148 is somewhat insensitive to ac voltages

a.

superimposed upon a dc signal at the input terminals.

However,

ac voltages which are

large compared with the dc signal may drive the Model 148 ac amplifier into saturation,

erroneously producing a dc output

at

the demodulator.

Therefore, shield the circuit to

the Nanovoltmeter input, particularly for low-level sources.

14

1067

MODEL 148 NANOVOLTMETER OPERATION

Improper shielding can cause the Model 148 to react in one or more of

b.

the following ways:

Needle jitter or instability, from 10% to 20% of full scale.

1. High offset (dc bias). Changing the power cord polarity or the

2.

connection between the LO and GND terminals may affect the amount of offset.

Slow response time, sluggish action and/or inconsistent readings

3.

between ranges.

Amplifier saturation.

4.

Observe the wave form with an oscilloscope connected to the DEMODULATOR TEST Jack (Figure 3). With the input shorted, it should approximate the wave form shown in Figure 6. If excessive pickup occurs, the wave form will resemble that of Figure 7. The circuit

will operate reasonably well as long as the wave formis not clipped, as

shown in Figure 8.

---

FIGURE 6.

Normal Wave Form at Demodulator with Input Shorted. Scale is 0.1 v/cm vertical and 10 msec/cm horizontal.

At this point a dc offset is introduced.

FIGURE 7.

Wave Form at Demodulator

Shown with Some Pickup. are adequate; some noise.

there is no offset but

Scale is 0.5 v/cm vertical

Measurements

and 10 msec/cm ho,rizontal.

0365

FIGURE 8. Wave Form at Demodulator when

Amplifier is Saturated. DC offset is intro-

duced and there is greater noise. Note the

Nanovoltmeter still reacts to the input signal,

Scale is 5 v/cm vertical and 10 msecfcm horizontal.

15

OPERATION

To minimize pickup, keep the voltage source and the Nanovoltmeter away

c.

from ac sources. at the low side of the input or at the LO terminal. magnetic flux is proportional to the area of the loop.

areas in the shield connections as well as the input circuitry.

at only one point. Run all wires in the circuit along the same path, so the

loop area is only the small difference in position of two adjacent wires.

Shield as carefully as possible.

MODEL 148 NANOVOLTMETER

Connect all shields together

The voltage induced due to a

Therefore, minimize loop

Connect the shield

Strong third harmonic magnetic fields

d.

create an 8-cps beat at the Nanovoltmeter output and meter.

effect, turn off all possible nearby sources,

Remove the Model 148 and the measuring circuit as far as possible from the magnetic field.

as electrostatic shielding around the circuit may be necessary.

tion concerning your particular shielding problem, 1322 North Elston Street, Chicago, Illinois.

Shielding is preferable to input filters.

e.

add noise (see Johnson noise equation), tracted from the maximum source resistance in Table 2. filters tend to create loop instabilities with the Nanovoltmeter. across the input, however,

be used to filter ac components in some cases.

2-14.

velop an emf if there is a temperature difference between the metals.

may be seen by blowing on one junction and checking the meter indication.

b. Thermal emf's can cause the following problems:

THERMAL EMF'S.

Junctions between two dissimilar metals form a thermocouple and will de-

a.

Meter instability or zero offset much higher than expected. Note,

1.

though, the Model 148 can have some offset (paragraph Z-5).

If removal does not greatly reduce the beat, magnetic as well

is less likely to cause loop instabilities, and it may

- 180 cps for ho-cps units - may To reduce this

such as heavy-duty transformers.

For informa-

contact Perfection Mica Corp.,

Resistive-capacitive filters

and the resistance value must be sub-

Inductive-capacitive

Capacity alone

This effect

Meter is very sensitive to ambient temperature differences.

2.

seen by touching the circuit, by putting a heat source near the circuit, or

by a regular pattern of instability, corresponding to heating and air con-

ditioning systems or changes in sunlight.

To minimize the drift caused by thermal emf's, use metals having the same

c.

thermoelectric powers in the input circuit.

have a thermoelectric power within about i0.25 pv/"C of copper. This means a

temperature unbalance of l°C between these metals would generate a thermal emf of about 0.25 microvolt. power of about 320 IJ-v/'C, copper. of materials. Since the Model 148 input circuit is made of pure copper, use

metals with nearly the same thermoelectric power.

to copper; however,

mal emf on the order of a few nanovolts per OC.

all necessary equipment to make very low-thermal copper crimp joints.

16

Standard physical handbooks contain tables of thermoelectric powers

slight amounts of copper oxide will cause a very slight ther-

At the other extreme, germanium has a thermoelectric

and silicon will develop about 420 pv/OC against

Gold, silver and low-thermal solder

The best junction is copper

The Model 1483 Kit contains

This is

0375

MODEL 148 NANOVOLTMETER

OPERATION

Several other techniques will reduce the effects of thermal emf's.

d.

the zero suppression circuit to buckout constant voltages.

from "pen windows, fans, temperatures. solder,

such as supplied in the Model 1483 Kit.

If connections must be soldered, use only cadmium-tin low-thermal

air conditioning vents and similar sources which vary

Unl.ike metals - including

Keep all circuits

USC?

regular solder - may be used and low thermal cmf's obtained if a well-controlled oil bath or a good heat sink is used.

Thermal voltages may be calculated Cram the thermoelectric power of the materials in the junction and the possible temperature difference between the junctions.

2-15. CIRCUIT CONNECTIONS.

When measuring in the microvolt and nanovolt regions, consider the effect

a.

the physical connections will have on the potential being measured. IR drops,

which in most circuits are insignificant, now become important.

For example!,

No. 20 AWG copper wire has a resistance of approximately 10 milliohms per

foot.

produce five microvolts.

A l-milliampere current through a b-inch length of this wire will

To reduce this drop to 0.5 nanovolt would mean

using a wire 0.0006 inch long.

. Four-terminal connections can

, ,

often be used to eliminate this error. Refer to Figure

If

an

9.

unwanted IR drop is con-

j ;it the zero suppress may be used

to nullify the voltage.

~ 1 M":::d:48 1

d. '

If the currents or resistances

I /

FIGURE 9.

Using Model 148 with

4-Terminal Connections.

in the measuring system fluctuate, they will develop fluctuating voltages

which will appear as noise or drict

in the system.

2-16. OPERATING FROM SOURCE OTHER THAN 117 VOLT, 60 CPS.

If the ac power source is 234 volts,

a.

Line Voltage Switch on the back panel (Figure 3.)

l/8 ampere to l/16 ampere.

Use only 250-volt MDL fuses. No other adjust-

use a screwdriver to change the

Change the fuse from

ment is necessary.

For 50-cps ac power sources,

b.

Cl03 and C104.

The Model 148 can operate satisfactorily from 60 or 50-cps

change the sideband filter capacitors,

sources, but the best ac rejection is achieved when the filter is set for

the lint frequency.

(C104) for 50 cps.

Use Keithley part C105-.109M (ClO3) and C45-.0155M

Refer to Figure 23 for component location.

2-17. RACK MOUNTING. (See Figure 10.)

The Model 148 is shipped for bench use with four feet and a tilt-bail.

a.

'The Model 4002 Rack Mounting Kit converts the instrument to rack mounting

to the standard EIA (RETMA) 19-inch width.

To convert the Model 148, remove the four screws at the bottom of

b.

each side of the instrument case.

Lift off the top cover assembly with the

17

OPERATION

MODEL 148 NANOVOLTMETER

handles; save the four screws.

cover assembly, turn the two screws near the back.

will release the cover and allow it to drop off.

bail and replace the cover (2).

c. Attach the pair of rack angles (3)

previously

;he chassis with the two pawl-type fasteners at the rear. Store the top cover

with handles, feet and tilt-bail for future use.

Item

I k

See Fir. 10)

1

2 3

4 screw, Slotted, lo-32 UNC-2x1/4 (Supplied 5

removed. Insert the top cover assembly (1) in place and fasten to

Cover Assembly Cover Assembly, Bottom (Supplied with

Model 148) 17695B

Angle, Rack

with Model 148)

Front Panel (Supplied with Model

TABLE 5.

Parts List for Moi

To remove the feet and tilt bail from the bottom

The two pawl-type fasteners

Remove the feet and the tilt

o the cabinet with the four screws (4)

t

Keithley

Description Part No: Quantity

17162C 1

1

14624B 2

--- 4

148) --- 1

1 4002 Rack Mounting Kit.

,r. __--...

Z COVER ASSEMBLY

4

ACOVER ASSEMBLY

18

FIGURE 10.

Exploded View for Rack Mounting.

0464:

MODEL 148 NANOVOLTMETER CIRCUIT DESCRIPTION

SECTION 3.

CIRCUIT DESCRIPTION

3-1. GENERAL.

The Model 148 consists of a chopper demodulator system followed by a

a.

dc amplifier.

Feedback is applied to the whole loop. (See Figure 11.)

b. A mechanical chopper converts the dc input signal to a 94-cps signal 'The ac signal is amplified, demodulated, dc amplified and applied co the meter.

it to the input.

A feedback network samples the signal at the output and compares

The dc input signal and the feedback signal are compared in the input transformer primary. The transformer increases the voltagedifference signal between the two. The ac amplifier amplifies the difference signal; line-frequency sidebands of the 94-cps signal are filtered

out. The a~ signal is then demodulated by a saturated transistor switch and enters a dc amplifier, which has a feedback capacitor to filter out

the demodulator ripple. The dc amplifier output is connected to the

meter, the output terminals and the feedback network. The feedback resistors determine full-scale range. The zero suppress signal is connected to the feedback point in the input circuit.

FIGURE 11. Block Diagram of Model 148 Amplifier Circuits.

The power source for the Model 148 is either line voltage or the

c. rechargeable battery. Voltage from either source is applied to a dc-todc inverter and then to three highly regulated supplies. The three

supplies furnish power to the oscillator and the amplifier circuits.

There

is also a battery charging circuit to charge the battery when it is necess-

ary and when the line voltage is connected.

NOTE

The circuit designations referred to in this section are for Schematic Diagrams 17351F, 17352D and 17353D found at the back of the manual.

0464

19

CIRCUIT DESCRIPTION

MODEL 148 NANOVOLTMETER

3-2.

INPUT CIRCUIT. The dc input signal is connected through the high terminal of the INPUT

a.

Receptacle, JlOl, to the center contact of the mechanical chopper, GlOl.

(See Figure 12.) The feedback signal is applied to the center tap of the input transformer, TlOl. .The chopper alternately applies a positive and a negative square-wave signal across each half of the primary. The magnitude of the square

wave is proportional to the difference between the dc input and the feedback

signals.

TlOl steps up this signal and applies it to the grid of tube Vl.

Chopper

1

0

L

t

"in

VO

FIGURE 12. Model 148 Input Circuit.

The dc input signal, Vin, is applied to the mechanical chopper. The feedback signal, Vf (the dc amplifier output voltage, Vo, applied to the transformer primary. The signal, Vd, transformer is

the

difference between the two, Vd = Vin - Vf, When

times the feedback ratio,,@ ), is

stepped up by the

the dc input signal is initially applied to the Model 148, Vf is zero and the voltage across the primary is entirely Vin.

voltage rises, Vf increases and Vd

decreases to a small value.

As the output

Vf = Vinj OrgV, = Vin. Only beta, which depends upon the RANGE and

FUNCTION Switch settings, determines the amplifier gain.

The input compartment is designed to insure high thermal stability and

b.

to minimize internal ac pickup.

Thermal stability is obtained in part by using only copper wire in the

1.

input circuitry. The input transformer primary and the mechanical chopper leads

are pure copper.

the mechanical strength without creating large thermal emf's.

portion of the FUNCTION Switch uses pure copper pins and rotor.

to components are made with pure copper crimp lugs.

The input connector is 99.5% copper; the impurities add to

The low voltage

All connections

Connections between

components are made by bolting the lugs together - not soldering - to reduce

thermal emf's.

The input compartment is doubly shielded against magnetic and electrostatic

2. pickup on all sides. The wires are physically placed to maintain minimum loop area, further minimizing pickup.

20

0464

MODEL 148 NANOVOLTMETER

The feedback network is formed from the output of the dc amplifier bacl;

c.

to the center tap of the primary of transformer TlOl.

selects the feedback ratio used for each range.

3-3. AC AMPLIFIER.

The ac amplifier circuit amplifies the 94-cps difference signal which

a.

corresponds to the dc input signal. The signal is applied to the grid of Vl and further amplified by tube V2. provides a high impedance load for V2.

transistors 44 and Q6. Potentiometer R109, between the Q3 emitter and Q4

base, adjusts the gain to compensate for beta variations.

each stage has some local degeneration. matching. The difference signal is amplified by transistors (27 and 98, which also form a full-wave signal for demodulation.

A series high-Q filter from the plate of V2 to circuit ground provides

b. notch rejection at the power-line frequency sidebands. pacitors Cl03 and Cl04 depend upon the power-line frequency. high Q of the inductor,

for 60-cps power lines and 44 cps and 144 cps for 50-cps power lines. ac amplifier's 94-cps gain and phase characteristics are affected very

little.

the filter forms sharp notches at 34 cps and 154 cps

A low-noise silicon transistor, Q3,

The signal is then ampl~ificd by

Transistor 95 is for impedance

CIRCUIT DESCRIPTION

The RANGE Switch, SlO2:

In addition,

The values of ca-

Due to the

ThC

The tube type and bias point of Vl are selected for low-noise oper-

c. ation at 94 cps. The high-Q tuned circuit in the plate of Vl has a good signal-to-noise ratio, and it provides a narrow bandwidth around 94 cps. The tuned circuit's Q is lowered on the higher ranges for amplifier stability.

3-4. DKMODULATOR.

switch demodulator. into a dc voltage with ripple component. Resistors R123 and R124 sum the

voltages from each to form a full-wave rectified signal. Jack 5102 allows

access to observe the waveform. The 94-cps oscillator furnishes a square-

wave drive for the demodulator.

3-5. DC AMPLIFIER.

The demodulator signal is amplified by two low-drift, high-gain silicon transistors, Qll pensate for temperature drift. Transistors Q13 and Q14 form the second amp-

lifier stage.

- transistors Q15 and Ql6 in pnp-npn configuration - draws little current at zero output. Diodes DlOl and D102 limit the output current, protecting Ql5 and Q16.

b. A feedback loop with capacitor Cl15 around the dc amplifier acts as an integrator, filtering the ripple component of the demodulated waveform. The effective capacity, which is approximately the value of Cl15 times

the dc amplifier gain, the response speed of the system. The capacitive feedback also lessens the noise in the amplifier outside the system bandpass.

Total gain is about 500.

Q9 and QlO in inverted configuration form a transistor

They convert the 94-cps wave from the ac amplifier

and 912, in differential configuration to com-

The emitter follower output stage

and the feedback factor (or open-loop gain) determine

0464

21

CIRCUIT DESCRIPTION

MODEL 148 NANOVOLTMETER

3-6. OSCILLATOR. phase-shift network for a 94-cps signal,

a transistor switch and phase compensation network for the square-wave demodu-

lator drive.

a. The phase-shift network consists of capacitors C301 through C303, resistors R319 through R321, and the combined resistance of R303 and R318, which bias transistor Q17. The input impedance of the emitter follower, 917, has little

loading effect on the effective value of this last resistance. Transistor Q18 compensates for signal losses in the phase-shift network.

adjusts the signal frequency.

miniature tube, Raytheon CK6418, provides variable degeneration to maintain a sine wave output to the next stage.

From the phase-shift network, the signal is amplified and used to drive

b.

the chopper. Transistor Q19 matches the impedance of transistor 920 to the

phase-shift network. Potentiometer R313 adjusts the signal amplitude.

transistor Q20, the signal is applied to the primary of transformer T301,

which drives the class B stage, transistors 922 and 923. After amplification

the sine-wave signal is applied to the mechanical chopper, GlOl. Transistor 921 develops the bias voltage for the class B stage, providing ambient temperature compensation for the chopper-drive signal amplitude. transformers T301 and T302 supply dc current for the class B stage.

The chopper drive signal is also applied to the primary of transformer

T3;;.

ting network,

for the chopper phase shift.

cut off to form a square-wave drive for the demodulator, transistors Q9 and QlO.

The transformer drives transistors Q24 and Q25 through a phase-compensa-

The oscillator circuit, stable to 0.1 cps, has three parts:

an amplifier to drive the chopper, and

Potentiometer R319

Resistor R322, the filament of a low-power sub-

From

The center taps of

resistors R308 to R310, R323 and capacitor C309, which compensates

The transistors alternate between saturation and

3-7.

from the power supplies to buckout steady background potentials in the input

signal. The lo-turn FINE Control, potentiometer R168, is connected between

-12 and +12 volt outputs.

Switch, S103, further divide the voltage.

in the MILLIVOLTS position,

primary of transformer TlOl.

ition,

copper resistor R137A, and a copper resistor R141. Using copper resistors for

the lowest voltage points shunted by evenohm resistors provides thermal and re-

sistive stability. 3-8. POWER SUPPLIES (See Figure 13.) The power supply for the Model 148 is

powered by an unregulated supply from the line voltage or rechargeable battery.

Either source feeds a dc-to-dc inverter and three highly regulated supplies

with outputs of +12, -12, and +1.2 volts.

circuits.

through the POWER SUPPLY Switch, S201.

is charged if necessary and the power supply uses line voltage. is in OFF, the battery charging circuit will operate if necessary; all other circuits are off.

battery;

ZERO SUPPRESSION.

the suppress voltage is divided by an evenohm, 0.25% resistor, R140,

a. The line voltage, battery and battery charging circuit are controlled

When the switch is in BATTERY, the power supply usas the

the other two circuits can not operate.

The zero suppress circuit provides a regulated voltage

The resistors R165 to R167 and R172 in the COARSE

When the FUNCTION switch, SlOl, is

the suppress voltage is applied directly to the

When the FUNCTION Switch is in MICROVOLTS pos-

These power all the other Model 148

When the switch is in AC, the battery

When the switch

22

0464

MODEL 148 NANOVOLTMETER

CIRCUIT DESCRIPTION

FIGURE 13. Block Diagram of Model 148 Power Supplies.

The unregulated supply consists of a full-wave rectifier, diodes

b. D212 and D213, and a dropping resistor, R232. The AC CONNECTED Lamp, DS201, is in series with resistor R226, which is connected directly

across this supply. For battery operation the primary of transformer

T201 is disconnected.

Voltage from the unregulated supply or the battery is applied to the

c. dc-to-dc inverter circuit. Transistors 428 and Q29 form a switching network to supply an interrupted voltage to transformer T202.

quency is about 2 kc, well away from the carrier frequency. has a saturable ferrite core.

The inverter circuit supplies voltages to

The switching fre-

Transformer T202

the three regulated supplies, which are basically the same series regulator

design.

For the +12 volt supply, diodes D206 and D207 full-wave rectify the

d. signal from transformer T202.

Q30.

The output of Q30 is divided by resistors R208 and R209 and compared

to the zener diode reference, D205.

The signal is applied to the pass transistor,

Transistors Q34 and Q33 amplify any potential difference and apply a signal t,o the base of transistor 932. Diodes D204 and D205 fix the emitter voltage of 432; therefore, the

collector voltage of Q33 directly determines the current through Q32,

which comes from the -12 volt supply.

The current drop through resistor

R216 determines the voltage at the base of transistor Q31, and therefore

.the output voltage through the base-emitter junction.

Diode D203 limits

0464

23

CIRCUIT DESCRIPTION

MODEL 148 NANOVOLTMETER

the base-to-emitter voltage of the 430 and 931 combination, thus also limit- * ing the current which it will pass. Diode D203 protects the pass transistor, Q30, if output of the supply is shorted,

For the -12 volt regulated supply,

e. the signal from transformer T202. Q35.

The output of Q35 is divided by resistors R217 and R218, thereby compar-

The signal is applied to the pass transistor,

diodes D210 and D211 full-wave rectify

ing it to the +12 volt supply, using ground as a reference. Transistors 938 and 939 amplify any potential difference and apply a signal to transistor Q37.

Transistors Q35 and Q36 form a Darlington combination, and work similarly to

that in the ,112 volt supply. The differences are that the -12 volt supply draws a higher current than the +12 volt supply, and therefore uses two diodes, D208 and D209, to protect the pass transistor. The negative "bootstrap" current supply is from a filter, resistor R225 and capacitor C210.

The +1.2 volt supply operates in the same manner as the 1~12 volt supply

f.

with these differences. The output of the pass transistor, Q40, is compared to

the output of the t12 volt supply divided down one tenth. The operating voltages for the comparator stage, 443 and 444, are obtained from the -h2 and -12 volt supplies.

Except for the comparator stage, npn transistors are used.

3-9. BATTERY CHARGING CIRCUIT.

The battery charging circuit operates when the POWER SUPPLY Switch, 5201,

a. is in AC or OFF position, and only when the battery needs charging.

The battery voltage is compared to a reference by two cascaded transistors,

b. 926 and Q27. When it is low, a charging current from transformer T201 is applied to the battery through the BATTERY CHARGING lamp, DS202, transistor 927 and diode D216. The reference is zener diode D214; the reference voltage is adjusted by

potentiometer R228. The difference between the battery and the reference poten-

tials determines the magnitude of the charge current through Q27. A silicon diode, 0216, prevents the battery from being run down because of leakage currents through Q27,

a germanium power transistor.

Diode D215 limits the base-to-

emitter voltage of the Q26 and Q27 combination, so no more than 400 milliamperes

(the rated maximum charge current of the battery) can flow in the circuit.

This circuit protects the battery. It decreases the charging current to

c.

a trickle-charge rate as the battery terminal voltage approaches the reference

voltage. It also limits the charge current if the battery was used beyond its

ampere-hour capacity, Note, however, that the battery can be damaged if it is used far beyond its capacity. A polarity reversal of a cell may occur, causing heavy circulating currents within the battery.

24

0464,

MODEL 148 NANOVOLTMETER

MAINTENANCE

SECTION 4.

4-1. GENERAL.

Section 4 contains the maintenance, troubleshooting and c.libratzon pro-

a. cedures for the Model 148. closely as possible to maintain the instrument's specifications.

The Model 148 requires no periodic maintenance beyond the normal care

b. required of high-quality electronic equipment. Components operate well below

maximum ratings. Principal maintenance is an occasional chopper replacement.

(See paragraph 4-3.) Occasional verification of meter calibration should show

any need for adjustment. 4-2.

ponents of the Nanovoltmeter. only reliable replacements which meet the specifications. The Model 148 uses no special critical parts except for resistor R322, which is a subminiature

tube filament, 80164 in the Replaceable Parts List are purchased only from Keithley Instruments or its distributors.

PARTS REPLACEMENT.

The Replaceable Parts List in Section 5 describes the electrical com-

a.

and the components listed in Table 6.

It is recommended these procedures be followed as

Replace components only as necessary, and use

MAINTENANCE

Make sure parts coded

The physical location of components in the input compartment is critical.

b.

Place replacement parts in the exact position shown in Figure 14. Circuit loops will introduce extraneous ac signals; see paragraph 2-13. The order of the copper lugs on the insulated posts greatly affects offiset and noise in tllc

Model 148. Tag or record the number on each lead as it is removed.

in reverse sequence. them. When replacing these parts, such as Scotch-Brite found in the Model 1483 Kit, or its equivalent. the procedures necessary for good low-thermal connections.

Battery pack assembly

Mechanical chopper assembly (See paragraph 4-3.) GlOl

Input connector assembly JlOl Copper feedback resistor assembly Evanohm resistor assembly R139

Evanohm resistor assembly R140 Evanohm resistor assembly Function switch plate assembly

Input transformer assembly

TABLE 6.

crimped on them and the proper lead length. for replacements; follow instructions given in paragraph 4.-Z.

Model 14,8 Pre-assembled Components.

Table 6 lists components which have lugs crimped on

clean the lug with a non-metallic abrasive,

Circuit

ComDonent

Desig. BA201

R137

R14.1 SlOl TlOl

These parts have lugs

Use only Keithley parts

Replace

Follow

Keithley Part No.

Model 148'

17689A 17638A 17627A 17635A 17636A

17637A 16883A 17623B

1266

25

MAINTENANCE

MODEL 148 NANOVOLTMETER

FIGURE 14.

Model 148 Input Compartment.

If replacing, duplicate location and order of leads on posts.

Note exact physical location of parts.

Figure 21 gives

circuit designations.

4-3.

mechanical, it will eventually wear and become noisy.

MECHANICAL CHOPPER REPWXMKNTS.

a. The mechanical chopper

is

designed for long life. However, since it is

At this point, replace-

ment is necessary.

Removal Procedures.

b.

Disconnect the chopper drive coil at connector 5302 (Figure 20).

1. Carefully remove the three thumb screws in the input compartment and the three chopper lead lugs.

Carefully slide the degaussing coil, L302 (Figure 20), from the chopper

2. body; remove the old chopper.

Replacement Procedures.

c.

Slide the degaussing coil, L302, over the new chopper body from the bottom.

1.

Orient so that the cut-out in the coil fits over the chopper drive lead.

2. Mount the chopper and coil in the input compartment.

Dress leads as

shown in Figure 14.

26

0365

MODEL 148 NANOVOLTMETER

MAINTENANCE

Check the instrument for proper operation.

3.

subparagraph b, steps 1, 2 and 3.

Degaussing Coil Adjustment Procedures.

d.

With the input shorted,

1. a signal through the Model 148. Use a differential input to the Type 503 Oscilloscope (-i- and - inputs) to observe the wave form between the emitters

of transistors Q9 and QlO (Points P and Q, Figure 25).

The wave form amplitude varies as the degaussing coil is moved along

2.

the chopper body. Potentiometer R301 (Figure 21) determines the effect of the coil on the wave form. Adjust both the coil and the potentiometer for

minimum amplitude. Reverse the red and black leads to the degaussing coil

if necessary.

An 8-cps beat at points P and Q may be present. Use battery opera-

3.

tion to reduce the beat; refer to paragraph 2-3.

4-4.

might occur in the Model 148.

only specified replacement parts. troubleshooting. tact Keithley Instruments or its representatives. Paragraph 2-17 describes how to remove the Nanovoltmeter cover.

TROUBLESHOOTING. The following procedures give instructions for repairing troubles which

a.

If the trouble cannot be readily located or repaired, con-

use the ZERO SUPPRESS Controls to generate

Use these procedures to troubleshoot and use

Table 7 lists equipment recommended for

Follow paragraph 4-9,

Paragraphs 4-6, 4-7 and 4-8 give step-by-step procedures for trouble-

b. shooting and checking out the power supply, Follow these in the order given.

tables for these circuits. components and to determine their function. 17352D and 17353D, contain the voltages at certain points in the circuit.

Before troubleshooting inside the Model 148, check the

external circuits (paragraph 4-5). Always check out the

power supply and the oscillator circuits before touching

the amplifier circuits.

pear faulty only because of a defect in the power supply

or oscillator circuits.

4-5. PRELIMINARY TROUBLESHOOTING PROCEDURES.

Before troubleshooting,

a.

Isolate the Nanovoltmeter from all external effects:

Disconnect all outside circuits from the INPUT and OUTPUT Recep-

1.

tacles,

and GND and LO terminals.

Also refer to Section 3 to find the more crucial

Tables 9,

NOTE

The amplifier circuits often ap-

check the outside circuits to the Model 148.

oscillator and amplifier circuits.

10 and 12 are troubleshooting

The Schematic Diagrams, 17351F,

0972

27

MAINTENANCE

MODEL 148 NANOVOLTMETER

Use

Monitor oscillator frequency.

Keithley Model 662 Cuardrd DC Differen-

tial Voltmeter RCA Model WV98113 Sunior Vol.tohmyst, 11 m

input resistance,

.!3-;< accuracy, 0 to 1500

Check voltage at output term-

inals.

Check dc voltages through-

out circuits.

volts dc.

Tektronix Typ? 503 Oscilloscope, dc to 450 kc.

'CABL,C 7.

Equipent

Recommended for Troubleshooting and Calibrating

Check wave forms for troubleshooting and calibrating.

then Model 148. 'USC. these instruments or their equivalents.

Connrci. ii low-therraal short across the INPUT Receptacle.

2.

The best connector ins a I%&1 1486 male low-thermal connector with a short length of pure CUI)~:~I: No. 18 or No. 20 wire rimped between the two pins.

The

next best is a Hodcl 1481 Low-Thermal Input Cable with the clips connected

together‘

!0xr) the cable as far as possible from ac sources, and avoid a

loop where i:h,~: alligator clips are connected.

Set t.lh,. Z'KRD SUPPRESS COARSE Control to OFF.

3. 1f hac:~~-~:~~~~ operation is trouble free, set the POWER SUPPLY Switch to

b.

BATTERY.

li!sconnect the power cord from the power line. Battery operation

eliminates maoy ground-loop connection problems with the test equipment.

lf a<. opc?ration is used, check the Line Voltage Switch for correct

c.

position and hire Fuse for correct rating.

NOTE

Often; after checking out according to paragraph 4-5, the Model 148 wj.11 ilunction normally, This points to problems in the circuits

outs:iGt the Nanovoltmeter. Refer to Table 4 to check the external circuit.

4-6.

Model 148

CHECK WI' AND CALIBRATION PROCEDURES. The following procedures give the steps

a.

circuits.

If a circuit fails to check out at any point, refer to

to

check out and calibrate the

the circuit's troubleshooting table. Continue as long as the points check

out. Use the equipment listed in Table 7.

Procedures

b.

are given for the power supply, oscillator and amplifier circuits. These clover the principal adjustments to bring the instrument within speclficntions.

28

1067

MODEL 148 NANOVOLTMETER MhINTENANCE

If the Model 148 is not within specifications after performing these

C.

checks and calibrations, return the unit to Keithley Instruments for further checkout, or follow the troubleshooting procedures to find the fault.

NOTE

Make sure the power supply and oscillator circuits arc

operating correctly before checking the amplifiers. All circuits depend upon properly functioning power supplies. If taken out of order. the resulting adjustment may be faulty.

4-7.

POWER SUPPLY CHECK OUT AND CALIBRATION.

a. All circuits depend upon the power supplies. Therefore, the ~+12,

-12 and +1.2 volt outputs mst be operating correctly before further checks are made. If the power supply fails to check out at any point,

refer to Table 9. After clearing the trouble, continue the check.

Procedures for CheckFng Regulated Power Supplies.

b.

Set

Connect the low-thermal shorting plug to the INPUT.

1.

the

Model 148 controls as follows:

POWER SUPPLY Switch OFF RANGE Switch

100 FUNCTION Switch MILLIVOLTS ZERO SUPPRESS COARSE Control OFF Line Voltage Switch Set to line voltage

Plug in the power cord. The AC CONNECTED Lamp should light.

2.

Measure the voltage at the Yellow-White wire on the POWER SUPPLY

3.

Switch front deck (Point A, Figure 20). It should be -18 volts dc ,2 vdc.

4. Turn the POWER SUPPLY Switch to AC. Use the oscilloscope to check

the wave form at point E (Figure 26) in the dc-to-dc inverter. Wave form should resemble that in Figure 15.

Measure the signal levels and ripple with respect to low of the

5.

three regulated supplies. Table 8 gives the values.

Regulated

Power

SUPPlY

Test Point,

Signal Level,

Figure 21 Volts dc

Maximum Ripple, Resistance

Millivolts

Peak-to-Peak

+12 volt B 11.6 to 12.8 0.3

-12 volt C cl.2 volt D

TABLE 8.

Signal Level, Maximum Ripple and Resistance for Regulated Power Supplies.

11.9 to 13.1

1.16 to 1.28

2.0

0.2

9664

to Ground,

Ohms

850 2100 460 + 70

20!~ 3

29

MAINTENANCE

MODEL 148 NANOVOLTMETER

TROUBLE

No voltage at point Blown fuse. A (Fig. 20)

Irregular wave form Overloaded regulators at point E (Fig. 26)

Incorrect voltage at Defective D205, Q33, points B, C and D

(Fig. 21)

Incorrect voltage Shorted Vl or V2 only at point D filaments

(Fig. 21)

High ripple at points B, C and D

(Fig. 21)

PROBABLE CAUSE SOLUTION

D212, D213 or R232 OpelI.

Q29

Q34, 438 (0~. 439)s D204, D212

Defective Q43 or Q44

Defective oscillator

Defective D204, D212, D205, 433, 434, Q38 or Q39.

Check for shorted transformer T201 or wiring;

Check components; replace if

faulty. Check resistances at power supply

faulty. Check components; replace if

faulty.

Check Vl and V2 filament. Check components; replace if

faulty. See paragraph 4-8.

Check components; replace if faulty.

then replace fuse.

High ripple only at Defective Q43 and/or point D (Fig. 21)

Unable to adjust for Defective D214, R227,

-8.2v at

(Fig. 26)

High ripple at B, Low battery voltage. C and D (Fig. 21) on battery operation only.

TABLE 9.

c.

Connect the Nanovoltmeter to the ac power line. Put the POWER SUPPLY Switch in AC position.

Adjust potentiometer R228 (Figure 27) for this value.

point G

Troubleshooting Table for Power Supply and Battery Charging Circuits.

Procedures for Charger Circuit.

Disconnect the battery pack;

1.

Set the charger bias voltage to -8.1 volts dc at point G, Figure 26.

2.

444.

R228, R229 or 426.

do not let the terminals touch the chassis.

Check components; replace if

faulty.

Check components; replace if

faulty.

Charge battery (paragraph 2-4).

30

0664

MODEL 148 NANOVOLTMETER

MAINTEXANCE

FIGURE 15. 1nverter.

Correct Wave Form in dc-to-dc

Point E, Figure 26, was monitored.

Scale is 5 v/cm vertical, 0.2 msec/cm horizontal.

Connect the battery; make sure the polarity is correct (red to red).

3.

The positive side of the battery is ground. The BATTERY CHARGING Lamp should light,

showing the charging circuits work. The lamp brightness

directly indicates the charge current - the brighter the light, the

greater the current.

After connecting the battery pack,

4.

the bias voltage may change.

This is normal and no readjustment is required.

4-8. OSCILLATOR CHECK OUT AND CALIBRATION.

The oscillator circuit drives the demodulator and the chopper. If

a.

the power supplies check out, continue on the oscillator.

fails to check out at any point, refer to Table 10.

After clearing the

If the oscillator

trouble, continue to check.

Procedures.

b.

connect the Type 503 Oscilloscope and the Model 5512A Electronic

1.

Counter to point F (Figure 21).

Set the oscillator frequency to 94 cps to.1 cps with potentiometer

2.

R319 (Figure 28).

Set

3.

the oscillator signal amplitude to 15.4 volts peak-to-peak kO.2 v peak-to-peak, measured on the oscilloscope. tiometer R313 (Figure 28).

Check the wave form at point F.

4.

It should be essentially sinusoidal,

as in Figure 16.

0664

Adjust with poten-

31

MAINTENANCE

If transistors 42.1, 922 or Q23 are replaced, it my be necessary to change resistor R307.

bias for 422 and 423.

If it does not but resembles Figure 17, use a 15-kilohm resistor

16. for R307.

MODEL 148 NANOVOLTMETER

NOTE

A 27-kilohm resistor should provide the proper The wave form at point F should resemble Figure

Fl

in Oscillator Circui:t.

Scale is 2 v/cm &rtIcal,

2 msec/cm horizontal.

FIGURE 17.

Improper Wave Forms at Point F (Figure 21) in Oscillator Circuit. Wave A indicates the wrong bias; wave B is distorted. Scale for both is 2 v/cm vertical, 2 mseclcm horizontal.

32

0664

MODEL 148 NANOVOLTMETER MAINTENANCE

TROUBLE PROBABLE CAUSE

SOLUTION

Jnable to adjust fre- Shorted chopper drive Disconnect chopper at 5302. &lency to 94 cps

circuit Check for 94 cps at Q19 emitter

(Point H, Figure 28).

Check fol

shorted wiring and chopper coil.

Distorted, off-fre- Defective 417, 918 Voltage at point H should be 1 quency wave form

at

point H with chopper

or Ql9

to 2 volts peak-to-peak, sine

wave.

If not, check components;

disconnected replace if faulty. Low voltage, dis- Defective Q17, Q18,

torted wave form at Q19 or R322 (Fig. 17b)

Cheek components; replace if faulty.

>oint F

Defective 420, 421, Q22, Q23 or R313

Check the

voltages, y20 to Q23,

given on schematic 173531). Kc-

(Fig. 17 a or b) place faulty components.

Improper bias to

Adjust R307 as

in note.

922 and Q23 ( Fig. 17a)

Jnstable frequency. Defective 417, R319,

C301, C302, C303 or

Check components; replace if faulty.

Q17 or R319 are most

R321, R320, R303, R318 likely parts.

TABLE 10.

4-9.

AMPLIFIER CHECK OUT AND CALIBRATION. The check out and calibration of the amplifier circuits is divided

a.

into two parts:

Oscillator Circuit Troubleshooting Table.

operational check and gain calibration. The operational check does not have to be followed by gain calibration. the Model 148 operation. refer to Table 12.

After clearing the trouble, continue the check.

If the amplifiers fail to check out at any point,

NOTE

Check the power supply and oscillator circuits before adjusting the amplifiers.

If the other two circuits are changed, the

amplifier circuit nay need recalibration.

Operational Check Procedures.

b.

Connect the low-thermal shc,.ting plug to the INPUT.

1.

panel controls as follows:

POWER SUPPLY Switch RANGE Switch 0.3 FUNCTION Switch ZERO SUPPRESS COARSE Control

ZERO SUPPRESS FINE Control

Use this to check

Set the front

BATTERY

MICROVOLTS

OFF At

one

end of rotation

0664

33

MAINTENANCE

MODEL 148 NANOVOLTMETER

On the 0.3-microvolt range,

2.

0.2 microvolt (66% of full scale). plug is not used.

Switch the ZERO SUPPRESS COARSE Control to 1; the meter should

3.

shift 0.2 to 0.16 microvolt.

Connect the Type SO3 Oscilloscope to the Model 148 OUTPUT. Set the

4.

oscilloscope amplifier to dc coupling,

second/cm. SUPPRESS COARSE Control to 1 to obtain a O.l-microvolt signal. The response time (from 10% to 90% of final value) should be between 0.2 and 0.4 second.

Adjust potentiometer RlOV (Figure 25) for this value.

To properly calibrate the Model 148 amplifier gain, an accurate micro-

c. volt-millivolt source is necessary. very much on the source. gain be calibrated by Keithley Instruments. here are some guides.

Set the Model 148 to the 0.1~microvolt range. Set the ZERO

Potentiometer RlOV Is a critical control. It adjusts the amplifier gain which affects Jutput ripple, source resistance as well as response time. Adjust this control only if one of these characteristics is slightly out of specifications.

If one is not available, it is recommended that the

the meter offset should be less than

It may be higher if the shorting

0.2 volt/cm, time base to 0.1 or 0.2

NOTE

input resistance and maximum

The value of this calibration depends

If a source should be constructed,

Use good low-thermal construction techniques (paragraph 2-10, and

1.

following).

The source accuracy is determined by the accuracies of the divider

2.

and the power supply.

Divide the source to the microvolt level with an accurate low-thermal

3.

divider.

low-thermal performance. Use standard ratio techniques to measure the exact ratio. If the R107 is used,

erature dependance of the divider to about 60 ppm/OC, from the resistance

temperature coefficient of copper of about 4000 ppm/OC.

Gain Calibration Procedures.

d.

1.

2.

Receptacle.

3.

Controls for zero output at the output terminals.

4.

should be 1 volt dc fl% for all ranges.

Keithley Part R107 is a good low-level copper resistor with good

Its 1OOO:l ratio is accurate to better than 0.5%.

shunt it with about an 100~ohm evanobm resistor. This reduces temp-

Connect the microvolt source to the Model 148 INPUT. Connect the Model 662 Differential Voltmeter to the Model 148 OUTPUT

Before applying power to the microvolt source, adjust the ZERO SUPPRESS

For a given full-scale input signal, measure the output voltage. It

34

1067

MODEL 148 NANOVOLTMETER MAINTENANCE

Check the resistors in the RANGE Switch by following the ranges in

5. Table 11. If these ranges check out, all ranges are within specifications. If a range fails to check, refer to Table 12. Rezero using the Zero Suppress Control before each check.

After calibrating the amplifier, adjust the input voltage (or zero

6. suppression) for full-scale outputs as shown on the differential voltmeter,

on any range

from

1 microvolt

and above.

Adjust potentiometer R136 (Figure

25) for exactly full-scale meter deflection.

Resistor Used

Range

In RANGE Switch

100 Millivolts and all other ranges Rl37B, Rl39, R144

0.01 and 0.1 millivolt &J.@, Rl5Q

0.1 Millivolt

0.3 Millivolt 1 Millivolt 3 Millivolts

R170 R171 R145

R146 10 Millivolts R147 30 Millivolts R148 100 Millivolts and 100 Microvolts

R137 ratio

TABLE 11. Range Checkout.

If these ranges are correct, all Model 148

ranges are correct. If any fail,

check the listed resistor.

0664

35

TROUBLE

PROBABLE CAUSE SOLUTION

High zero offset Short in feedback network. Make sure lugs do not touch each other or

the copper plate in input compartment.

Check resistances.

Maladjusted degaussing coil. Adjust (paragraph 4-3).

Random zero drift, tens of nano- Noisy chopper Replace chopper; see paragraph 4-3. volts or more; sometimes reduced

if the cabinet slapped. Response speed is good.

Zero drift greatly affected by Maladjusted or dirty FUNCTION Loosen set ;xews on rotor hub (Figure slight movement of FUNCTION Switch. Switch within a setting.

); slide rotor zway from pins. Clean

rotor and pins with non-metallic abrasive.

Adjust such that the rotor is flush with

and makes contact with all three pins

consecutively, two at a time.

Zero drift very temperature sensitive.

Response speed very slow,

possibly offset also high. Cannot adjust to specifications

with R109.

TABLE 12 (Sheet 1). Amplifier Troubleshooting Table.

Contaminated INPUT Receptacle, Clean INPUT Receptacle with non-metallic

shorting plug, or connection abrasive. If contamination goes below

in input compartment.

plated surface, replace connector.

Clean

lugs with non-metallic abrasive; be sure

to return to posts in original order.

Low ac amplifier gain, due to

bad active element,

Set to O.l-microvolt range, ZERO SUPPRESS

COARSE to 3, FINE to an easily readable

signal. With oscilloscope, check for square wave at Vl, grid, and sine wave at input and output of each succeeding stage.

Check dc voltages, Vl through 98, given on

schematic 17351F. Replace faulty components

Improper amplifier phasing

See paragraph 4-10.

If it is incorrect,

use lissajous patterns to check phase from grid Vl through each stage to base Q7.

Shifts of up to about 300 dre acceptable,

Check capacitors and active elements.

TROUBLE

PROBABLE CAUSE SOLUTION

Response speed very slow,

possibly offset also high. Cannot adjust to specifications

with R109.

Demodulator does not "clamp" during one-half cycle (Fig-

ure 18).

Greater than 20-1~ peak-to-peak ripple at output terminals on ac power.

On battery operation,

output ripple is above 5 mv p-p. lOO-millivolt and all other

ranges out of calibration, all same direction.

Low gain in dc amplifier. Unsolder and lift one end of R123 and R124.

See points M and N, Figure 25. Apply 10 t( 1OOmv to base of Qll to zero meter.

Chang<

input by 1 millivolt; output should shift

0.3 to 3.0 volts. If not or if more than 1OOmv is required to zero, check transistors, beginning with Qll and Q12. Qll and

Q12 are matched for offset. Replace only

with parts purchased from Keithley. Leaky or shorted C115. Check; replace if faulty. Defective Q9, QlO, 424 Check for sine wave -t secondary of T302,

or 925. square wave at collector 924 and 925 and

base Q9 and QlO. Replace faulty componentr

Instrument located near high

HO-cps magnetic field, such by one.

Try turning off possible sources one

Move instrument from field

as poorly shielded heavy-duty source.

transformer.

R144, R139, or R137 out of Check resistors; replace if faulty.

tolerance.

Only 0.01 and 0.03~microvolt or millivolt ranges out of

calibration.

All microvolt ranges out of

calibration.

The millivolt

ranges are good. One range out of calibration.

TABLE 12 (Sheet 2). Amplifier Troubleshooting Table.

R149 or R150 out of tolerance. Check resistors; replace if faulty.

R137, ratio B to A out of

Check resistor; replace if faulty.

tolerance.

Corresponding resistor in

Check resistor; replace if faulty.

Table 11 out of tolerance.

MAINTENANCE

MODEL 148 NANOVOLTMETER

FIGURE 20. Top View of Model 148 Chassis.

circuits and some test points is shown above. circuit designations.

38

Location of components, printed

Refer to Parts List for

0365

MODEL 148 NANOVOLTKETER

MAlNTENANCE

i

FIGURE 21.

test points is shown above.

Refer to Parts List for circuit designations.

* Connect to point F at either place,

Bottom View of Model 148 Chassis.

The input compartment is shown without its shield.

not to both points simultaneously.

0664

i

Locations of components and some

39

MODEL 148 NANOVOLTMETER

MAINTENANCE

FIGURE 24.

Resistor Locations on Printed Circuit 76.

contains callouts for the other resistors.

Figure 25

FIGUM 25.

Resistor and Test Point Locations on Printed Circuit 76.

Figure 24 contains callouts for the other resistors.

0365’

41

MAINTENANCE

MODEL 148 NANOVOLTMETER

FIGURE 26.

Resistor and Test Point Locations on Printed Circuit 74,

Bottom Face.

9~ Connect to point E at either place, not to both points simultaneously.

FIGURE 27.

42

Component Locations on Printed Circuit 74, Top Face.

0664

MODEL 148 NANOVOL'DIETER

MAINTENANCE

FIGURE 28. An alternate location for point H is shown in Figure 20.

Resistor and Test Point Locations on Printed Circuit 75.

0664,

FIGURE 29. Capacitor and Transistor Locations on Printed Circuit 75.

43

MAINTENANCE

MODEL 148 NANOVOLTMETER

FIGURE 30.

Switch (S102). on opposite side.

Resistor Locations on RANGE

Figure

0

FIGURE 31.

31 shows resistors RANGE Switch (5102). Figure 30

resistors on opposite side.

Resistor Locations on

0

shows

44

FIGURE 32.

component Layout For PC-402.

0664

MODEL 148 NANOVOLTMFTER

REPLACEABLE PARTS

SECTION 5.

5-1.

REPLACEABLE PARTS LIST.

ponents of the Model 148 and its accessories.

REPLACEABLE PARTS

The Replaceable Parts List describes the com-

The List gives the circuit designation, the part description, a suggested manufacturer and the Keithle; Part Number.

The last column indicates the figure picturing the part.

The name and address of the uunufacturers listed in the "Mfg. Code" column

are contained in Table 14.

5-2.

Keithley Part Number,

HOW TO ORDER PARTS. For parts orders,

a.

include the instrument's model and serial number, the

the circuit designation and a description of the part. All structural parts and those parts coded for Keithley manufacture (80164) must be ordered from Keithley Instruments, Inc.

in the Replaceable Parts List,

completely describe the part, its function and

In ordering a part not listed

its location.

Order parts through your nearest Keithley distributor or the Sales

b.

Service Department, Keithley instruments, Inc.

amp Cbvar

CerD Ceramic, Disc ComP

DC% EAl

EMC

.Sllpl2TY~ M.il. No. Military Type Number

MY

Mylar

Carbon Variable

n

ohm

Composition

PMP

Metalized paper, phznolic case

Deposited Carbon Poly Polystyrene

P

pica (10-12) Electrolytic, Aluminum Electrolytic, metal cased

Ref.

Reference ETB Electrolytic, tubular ETT

Electrolytic, tantulum

v

micro (10e6) f farad " volt

Fig.

hy

k

M or meg

Figure

henry

kilo (103)

mega (106) or megohms

Var

w

ww

Variable

watt

Wirewound

wwenc Wirewound encapsulated WWVar

Wirewound Variable

milli (10w3)

zfg.

Manufacturer

MtF Metal Film

0664

TABLE 13.

Abbreviations and Symbols.

45

REPLACEABLE PARTS

(Refer to Schematic Diagram 17351F for circuit designations)

MODEL 148

MODEL 148 REPLACEABLE PARTS LIST

CAPACITORS

Circuit Desig. Value Rating

Cl01 Cl02 Cl03 (60 cps)

Cl03 (50 cps) Cl04 (60 cps) Cl04 (50 cps) Cl05 Not Used

Cl06 Cl07 .012 vf Cl08 Cl09

Cl10 Cl11

Cl12 Cl13 Cl14 Cl15

Cl16

Not Used Cl17 Cl18

Cl19 Cl20

.0143 uf

100 "

O.Ol)lf 16 v CerD

.184 ILf .lOV llf .0135 bf .0155 ,Lf

.liJ.f .22 pf

100 v MY 100 v 100 " Poly

100 v Poly 50 "

50 v 100 v Poly

4.7 pf

10 v ETB

100 vf 15 v

.Ol i.lf

25

jkf

100 iJf 10 pf 10 pf 25 I-if

.05 pf 200 vf

0.047pf *

600 v CerD

16 v 15 v 20 "

20 v 10 v

600 v 3v 200 "

500 " POlY C201 Not Used C7.02 Not Used C203 Not Used

C204 c205

100 pf 100 Kf

15 v

15 "

TYPO

Polv

MY

MY MY

EA.1

ETB EAZ

ETT ETT ETT

(non-polar)

MY

EAl

MPF

FAl

EAl

Mfg.

Keithley

Fig.

Code Part No. Ref. 84171

71590

12673

C45-.0143M

C238-.OlM

C105-.184M 23

21 23

12673 Cl05-.109M 23 84171 C45-.0135M 84171

C45-.0155M 23

84411 C41-.lM 84411 C41-.22M

84171 C45-.012M 05397

29309 72982

56289

29309

05397 05397

05079

56289

14655

C71-4.7M C210-100M

C22-.OlM C104-25M

C210-100M

C80-10M C80-10M

C106-25M

C62-.05M C48-200M

23

23 23

23 23 23 23

23 23 23 23 23

21

c142-.O.O47M

71590

29309 29309

C-138-*

C210-100M

23 23

46

C206 c207 C208 c209 c210 c211

.Ol bf

100 vf

100 wf .Ol I.rf

100 IJ.f 100 iJf

600 v

25 v

15 -.I

600 v

25 v

CerD PMP PMP CerD PMP PMP

72982 C22-.OlM

29309 29309

C211-100M C210-1OOM

72982 C22-.OlM

29309 29309

C211-100M

C211-1OOM

Refer to page 52 for higher designations.

*Value selected at factory

DIODES

Circuit Desig.

TYPO

DlOl Silicon D102

Silicon

Number

IN645 IN645

Mfg.

Code 83125

83125

Keithley Part No.

RF-14 23

RF-14 D103 Zetler lN709 12954 DZ-21 ill04 zeIlC?r

lN709 12954 DZ-21

23 23

23 23 23 23

Fig. Ref.

23

0179

MODEL 148

REPLACEABLE PARTS

DIODES (Cont'd)

Circuit Desig.

TYPO

NUmber

Mfg.

Code Part

Keithley Fig.

No.

Ref.

D201Not Used D202Not Used

D203 Silicon 1~645 83125 RF-14 23 D204 Silicon lN645 83125 RF-14 23 D205 ZiXUXC Special 80164 DZ-13 23

D206 Silicon lN645 83125 RF-38 23 D207 Silicon lN645 83125 RF-38 23 D208 Zener, 2.6V

D209 Not

Used --- --- --- --

lN702A 01295 DZ-33

23 D210 Silicon lN645 83125 RF-38 23 D211 Silicon lN645 83125 RF-38 23

0212 Silicon lN645 83125 RF-14 23

Refer to page 52 for higher designations.

MISCELLANEOUS PARTS

Circuit

Desig. Description

Mfg.

Keithley

Code Part No. Ref.

Fig.

GlOl Chopper JlOl

Receptacle, INPUT, Special Plug, Special, Mate of JlOl

5102 Jack, Telephone, DEMODULATOR TEST (Mfg.

No. 275)

JlO3 Receptacle, Microphone, OUTPUT (Mfg. No.

---

80PC2F)

Plug, Microphone, Mate of 5103 (Mfg. No.

8OMCZM)

J202 connector (Mfg. No. PSC4SS15-12)

3301

5302

---

-ma

Connector (Mfg. No. PSC4=15-12)

Receptacle

. Locking Ring (Mfg. No. 126-1430) . Receptacle (Mfg. No. 126-1429) 02660 . Body (Mfg. No. 126-1425) 02660 CS-161

Binding Post, LO (Mfg. No. DF21BC) 58474 Binding Post, GND (Mfg. No. DF2lGC) 58474 BP-11G

80164 80164

80164

83330

02660 02660

09962

09962 02660

17689A 17638A

CS-132

CS-65

CS-32 cs-33

cs-175

es-165 CS-163

BP-11B

20

2

3

--

20

3 3

0179

---

Shorting Link (Mfg. No. 938-L)

24655 BP-6

_-

47

REPLACEABLE PARTS

MODEL 148

MISCELLANEOUS PARTS (Cont'd)

Circuit Desig.

LlOl L102

Ml01

SlOl a--

s102

---

--s103

---

--s s201

---

5202

Mfg.

Description

Choke, 200 hy Choke, 120/80 hy

Meter

Code Part No. 80164

80164 80164

Rotary Switch less components, FUNCTION 80164

Knob Assembly, Function Switch

Rotary Switch less components, RANGE

Switch Assembly with components, Range

Knob Assembly, Range Switch

80164

80164 80164 80164

Rotary Switch less components, ZERO SUPPRESS 80164

COARSE

Switch Assembly with components, Coarse 80164

Knob Assembly, Coarse Switch

80164

Rotary Switch less components, POWER SUPPLY 80164 Knob Assembly, Power Supply Switch

Slide Switch, 117 234

80164

Keithley Fig.

Ref.

CH-1 20

CH-5 20

MB-14 20

** 2 16323A

SW-157 2 17632B 163238

SW-58 2 17626B

14838A

SW-158 2 14838A

SW-151

Knob Assembly, Fine Potentiometer 80164

TlOl T202

Transformer

Transformer 80164

Circuit Desig.

Value

RlOl 68 kS, R102 Rl03

10 kn

4.7M0

R104 250 lin R105 22 kn

Rl06 250 k.fi Rl07 100 kn

R108

22

kn R109 100 ki2 RllO 4.7 kJi

Rlll

22

kn R112 27 ti R113 10 kQ R114 10 kn R115 470 n

RESISTORS

Rating

TYPO

.lO%, l/4 w Comp

lO%, l/4 w Comp lO%, l/2 w

Comp l%, l/2 w DCb lO%, l/2 w Camp

l%, l/2 w DCb lO%, l/2 w camp lO%, l/2 w Comp lO%, .2 w CbVar lO%, l/2 w Camp

lO%, l/2 w Comp lO%, l/2 w Camp lO%, l/2 w Camp lO%, l/2 w Camp

lO%, l/2 w Comp

15110A 2

80164

17623B 20

TR-65 20

Mfg. Code

Keithley Part No.

Fig.

Ref.

01121 ~76-681CC1 32 01121 R76-10Kn 32

01121 Rl-4.7M0 32 79727 RlZ-250K 25 01121 Rl-22K 24

79727 R12-250K 24 01121 Rl-100K 24 01121 Rl-22K 24

80294 RP40-100K 25 01121 Rl-4.7K 25

01121 Rl-22K 24 01121 Rl-27K 25 01121 Rl-1OK 25 01121 Rl-1OK 25

01121 Rl-470 24

48

we Contact

the factory

tar repiacement.

0179

MODEL 148

REPLACEABLE PARTS

RESISTORS (Cont'd)

Circuit Desig. Value

R116 R117 R118 Rl19

RI70

R121 R122 R123 R124 R125

R126 Rl27 RI28 R129 R130

R131 R132 R133 R134

4. 7 ko

4.7 kR

4.7 ksl

4.7 ba

8.2 kn 150 n

8.2 kn 10 kn 10 ka

50 kn

50 kil 250 n 120 ICQ 120 kcl 12 kn

12 ksl 25 kc,

470 (1

100 0

Rating

lO%, l/2 w

lO%, lO%, lO%,

lO%, l/2 w

lO%, lO%, l%,

l%, II2 w

l%, l%,

l%, l%, l%,

l/2 w l/2 w

II2 w

l/2 w

l/2 w l/2 w l/2 w

l/2 w

lO%, l/2 w

Type Comp 01121 Rl-4./K 24

Comp 01121 camp 01121 Rl-4.7K camp 01121 Rl-4.7K Comp 01121 Rl-8.2K

Camp 01121 Rl-150 Comp DCb 79727 R12-10K DCb 79727 R12-10K DCb 79727 R12-50K

DCb DCb 19727 DCb 79727 K12-120K DCb C0mp 01121 Rl-12K

lO%, l/2 w Comp 01121 RL-12K l%,

l/2 w

DCb lo%, 112 w C0mp 01121 Rl-470 lO%, l/2 w Comp 01121 Rl-100

R135 8,6 ko, l%, l/2 w DCb

Mfg.

Keithley Fig.

Code Part No.

Rl-4.7K

01121

Rl-8.2K

79727 R12-50K

Rl2-250

79727

Rl2-120K

Rl2-25K

R12-8.6K 25

Ref.

24 24 24 24

25 24 25 25 25

24 24 25 25 24

24 25 24 24

R136 R137A & B RI38 R139 R140

Rl41 R142 R143 R144 R145

R146

R147 R148 R149 R150

Rl51

2 kn 1 kn & li

Not Used

111 0

1.11 ks?

10 kn Not Used Not Used

900 (1 99 kc1

32.3 ICC2

9 ICS~

2.33 ki,

900 n

100 n

3.3 m

R152 %- 680 kil

R153 >'v 330 k0

Rl54

WOO kc)

Rl55 "47 kQ R156

R157

?<l ?G

330 Ia

lO%, Special

l/4%, 113 w l/4%,

5%, l/2 w

l/4%, L/3 w l/4%,

l/4%, l/4%, II3 w

l/4%, l/3 w

l/4%, 113 w

l/4%, l/3 w

10x>, l/2 w lO%, l/2 w

lO%, l/2 w

lO%, l/2 w lO%,

9: Nominal value, factory set.

l/2 w

l/3 w

l/3 w l/3 w

l/2 w

WWVar

80294

ww 80164 wwenc

wwenc

CO164 80164

Camp 80164

wwenc wwenc

wwenc wwenc wwenc wwenc

wwenc

C0mp Comp Comp C0Illp C0mp

camp Comp

01686 01686

01686

01686 01686 01686

01686

01121

01.121

01121 01121 01121

RP35-2K

17627A I.763511

17636A

17637A

K1.05-900 RlOS-99K

R105-32.3K R1.05-9K R105-2.33K

RlO5-900

R105-100

Rl-3.3M Rl-680K Rl-330K

RI-100K

RI-47K

RL-LM

Rl-330K

25 21

21 21

21,

31 30

30 30 31 31 31

30

31. 31 31 31

30 30

0972

49

REPLACEABLE PARTS

MODEL 148

RESISTORS (Cont'd)

Circuit Desig.

Value Rating

R158 150 ks2 lO%, l/2 w

R159 68 kfl

lO%, l/2 w

R160 22 kn lO%, 112 w R161 6.8 k~

R162 3.3 kn R163 1 kn R164 470 a R165 4.7 m

R166

1I"Tl

R167 100 kn R168 10 kn R169 "33 kn

R170 1 Xl R171 332 icn R172 10 kn

R173 15 k0

lO%, l/2 w lO%, l/2 w lO%, 112 w lO%, l/2 w camp l%, l/2 w

l%, l/2 w l%, l/2 w 3%, 1.5 w lO%, l/2 w l/Z%, I.12 w

il4%, l/3 w

l%, l/2 w

l%, 1/8W,

RZOlNot Used

R202Not Used R203Not Used R204Not Used R205Not Used

Keithley

TYPO

Mfg.

Code Part No.

camp 01121 Rl-150K 30 camp 01121 camp 01121

camp 01121 camp 01121

Rl-68K 30

Rl-22K 30 Rl-6.8K

Rl-3.3K

camp 01121 Rl-1K 31

01121 Rl-470

DCb 79727

DCb 79727 DCb 79727

wwvar 73138

Rl2-4.7M

RlZ-1M RlZ-100K

RP41-10K

camp 01121 Rl-33K

MtF 75042

R61-1M

wwenc 01686 R105-332K

DCb 79727

MtF

07716

RlZ-10K

R88-15K0

Fig. Ref.

31 31

31 e9<

?d< ?<9<

20 25 30 30

w<

32

R206Not Used R207 1 kn

R208 6.98 kb2

R209 6.98 kn R210 4.7 kn

R211 2.7 kn R212 6.8 kn R213

22

11 R214 2.7 ks, R215 15 kn

R216 22 kn R217 10 kn R218 10 k.Q R219 4.7 kn R220 10 kn

R221 10 ko R222 2.7 kn. R223 2.7 n

R224 4.7 kfi R225 1 kn

lO%, l/2 w l%, 112 w l%, l/2 w lO%, l/2 w

lO%, l/2 w lO%, l/2 w lO%, l/2 w lO%, l/2 w lO%, l/2 w

lO%, l/2 w l%, l/2 w l%, l/2 w l%, l/2 w lO%, l/2 w

l%, l/2 w lO%, l/2 w lO%, l/2 w lO%, l/2 w lO%, l/2 w

camp DCb DCb camp

camp

camp camp camp camp

camp DCb DCb DCb camp

DCb camp camp camp

01121

79727 79727

01121 01121

01121 01121 01121 01121

01121

79727 79727 79727

01121

79727 01121 01121 01121 01121

Refer to page 53 for higher designations.

k Nominal value, factory set.

e* These resistors are located in S103, Figure 20.

Rl-1K R12-6.98Kn

24

25 RlZ-6.98Kfi 24 Rl-4.7K 24

Rl-2.7K 24 Rl-6.8K 25 Rl-22 24 Rl-2.7K 25 Rl-15K 25

Rl-22K 25

RlZ-10K 25

Rl2-1OK 25 R12-4.7K 24 Rl-1OK

24

R12-10K 25 Rl-2.7K 25 Rl-2.7 24 Rl-4.7K

25

Rl-1K 24

50

0179

MODEL 148

REPLACEABLE PARTS

TRANSISTORS

Circuit Desig.

Ql FET

QZFET

Q3NPN, Case TO-106 2N5134 Q4NPN, Case TO-106 2N5134 Q5 2N1381

:; 2Nl381 2N1381 Q8 2N1381

Q~~NPN, QlZNPN,

Case TO-106 2N5134 Case TO-106 2N5134

413 414 2Nl381

Q15 2N1605A Q16 2N651

Mfr.

Desig.

D1422

2N1381 2N1381

2Nl381

Mfr.

D1422 DICK

07263 07263

01295

01295 01295

01295 01295 01295

07263 07263

01295 01295 02735 04713

Refer to page 55 for designations Q17 to 925 and to 930 2N1381

431 2N1381 432 2N1381 Q33 2N1381 434 2N1381

01295 01295 01295 01295 01295

Q35 PNP, Case TO-540139 02735

Keithley

Fig.

Part No. Ref.

TG-45 32 TG-45 32

TG-65 22 TG-65 22 TG-8 22

TG-8 22

TG-8 22 TG-8 22 TG-8 22 TG-8 22

TG-65 22 TG-65 22 TG-8 22

'TG- 8 22

TG-16 22

TG-9 22

page 53 for Q26 CO (229.

TG-8 22 TG-8 22

TG-8 22

TG-50 22

0179

Q36 437 Q38

Q39 Q40Not Used

Q41Not Used Q42Not Used

Q43Not Used Q44Not Used

Circuit Desig.

Vl

VZNot Used

2N1381 2N1381 2N1381 2N1381

01295 01295 01295 01295

TG-8 TG-8 TG-8 TG-8 22

VACUUM TUBES

Keithley Part No.

Number

Mfg.

Code

CK512AX 80164 EV-512AX

22 22 22

Fig. Ref.

21

51

REPLACEABLE PARTS

Refer to Schematic Diagram 17352D for circuit designations.

MODEL 148

NOTE

CAPACITORS

Circuit

Desig. Value Rating

Refer to page 46 for lower designations.

c212 500 kf 25 v IcAl

C213 500 IJ.f

C214

Refer to page 54 for higher designations.

Circuit

Desig.

Refer to page 47 for lower designations.

D212 D213 D214 D215

D216 D217 D218

D219

D220

.Ol pf

TYPO

Silicon Silicon ZfXXXC

Silicon

Silicon ZCSler ZCXltZr

Rectifier Rectifier

25 v

600 v CerD

Number

IN645 lN645 1N713 lN645

lN645 lN746A lN746A lN4148

1~4148

5Pe

FAl

DIODES

Mfg.

Code

56289 C94-500M 27

56289

72982

Mfg.

Code

83125 83125 12954 DZ-14 83125 83125 01295 01295 DZ-40 01295 01295 RF-28

Keithley Part No. Ref.

C94-500M C22-.OlM 27

Keithley Fig. Part No.

RF-l.4 RF-14

RF-14 RF-14 27

DZ-40 RF-28

Fig.

27

Ref.

27 27

52

Circuit Desig.

BA201 Battery Pack, 6-volt 4-amp-hr nickel-

cadmium

DS201

--DS202

---

F201 (117 v) Fuse, l/8 amp, 3 AG, type MDL

F201 (234 v) Fuse, l/16 amp, 3 AG, type hDL

---

F202 X01 Terminal Block (Mfg. No. 3008)

.I202

Bulb, AC CONNECTED, bayonet base (Mfg.

No. 49)

Light Socket, Red (Mfg. No. 81410-231)

Bulb, BATTERY CHARGING, bayonet base

(Mfg. No. 49)

Light Socket, Amber (Mfg. No. 81410-233)

Fuse Holder FUSS, 1 amp, 8 AG

Connector (Mfg. No. 02-018-013-5200)

MISCELLANEOUS PARTS

Description

Mfg.

Code Part No. Ref.

80164 Model 14,8920

08804 PL-23 72619 PL-5R

08804 PL-23

72619 PL-5A 71400 FU-20

71400 Fu-21 75915 FH-3 75915 m-1

83330 W-47

91662 CS-127

Keithley Fig.

2

21

3 20 20

20

0179

MODEL 148

REPLACEABLE PARTS

MLSCELLANEOUS PARTS (Cont'd)

Circuit Desig.

---

vs..

Line Cord Line Cord Clamp

Description

Mfg. Code

80164 CO-5 80164 CC-4

Keithley Fig. Part No. Ref.

3

5201 Rotary Switch (See pg. 48 ) 80164 SW-158

s202 Slide Switch, Line Voltage

80164 SW-151

3

T201 Transformer 80164 TR-63 20

RESISTORS

Circuit Desig.

Value Rating

TYPO

Mfg. Code Part No.

Keithley Fig.

RCf. Refer to page 50 for lower designations. R226 w20 0 .l%, 2 w ww 01686 R92-220 26

R227 330 n .l%, 2 w ww 01686 R92-330 27 R228 1 ki? lO%, l/2 w wwvar 80294 RP39-1K 27

R229 1.8 ku l%, l/2 w DCb 79727 R12-1.8K 27 R230 680 12 lO%, 112 w camp 01121 Rl-680 27

R231 10 n .l%, 2 w ww 01686 R92-10 26 R232 18 n .l%, 2 w ww 01686 R92-18 26 R233 100 (1 lO%, l/2 w CCJlllp 01121 Rl-100 27 R234 1.5 kn lO%, l/2 w camp 01121 Rl-1.5K 27 R235 1. 11 ww

R236 75 kR Deb R237 R238

10 k0 10 kn

lO%, l/4 w lO%, l/4 w

Comp Comp

01686 R92-1 20

79727 RlZ-75K 27 01121 R76-10K

01121 R76-10K

Refer to page 54 for higher designations.

TRANSISTORS

Circuit

Desia.

NUmber

Mfg. Code

Keithley Part No.

Fig.

Ref. Refer to page 55 for lower designations.

Q’J6 2N1372 02735 ~27 2Nl535 04713

9253

2N651 04713

929 2N651 04713

TG-8 27

TG-7 27 TG-9 27 TG-9 27

Refer to page 51 for higher designations.

ge Nominal value, factory set.

0179

53

REPLACEABLE PARTS

Refer to Schematic Diagram 17353D for circuit designations.

MODEL 148

NOTE

CAPACITORS

circuit

Desig. V.&-W Rating

TYPO

Mfr.

Keithley Part No.

Fig. Ref.

Refer to page 52 for lower designations.

c301 .22 pf 50 v MY 84411 C41-.22M 29 c302 .22 pf 50 v MY 84411 C41-.22M 29 c303 .l pf 50 v MY 84411 C41-.lM 29 c304 100 uf 15 v EAL 29309 C210-100M 29 c305 10 IJf 15 v PMP 56289 C93-10M 29

C306 100 jlf 15 v EAL 29309 CZlO-100M 29 c307 100 pf 15 v EAL 29309 C210-100M 29 C308

2

vf 50 " MPCb EC1 C-215-2M 21 c309 .22 I.lf 50 " MY 84411 C41-.22M 29 c310 470 pF 1ooov CerD 71590 DD-471 c311 470 pF 1ooov CerD 71590 DD-471

Circuit

Desig.

5301

J302

-__

---

--L302

T301

T302

Description

Connector (Mfg. No. 02-016-013-

5200)

Connector

. Nut (Mfg. No. 41-153) . Locking Ring (Mfg. No. 126-1428) 02660 . Plug (Mfg. No. 126-1427)

Degausing Coil

Transformer 80164 Transformer 80164

MISCELLANEOUS PARTS

Mfr.

91662 02660 02660

80164

Keithley Part No.

Fig. Ref.

CS-126 20 CS-160

CS-164 CS-162

CH-6 20

TR-64 21 TR-68 21

54

RESISTORS

Circuit

Desig.

Value Rating

Refer to page 53 for lower designations. R301

R302 R303 R304 R305

R306 R307

2n

'W n

12

Ml

ZL

8.2 ksl

a15 kcl lO%, l/2 w

lO%, 5 w lO%, l/2 w

lO%, l/2 w l%, l/2 w lO%, l/2 "

lO%, l/2 w

* Nominal value, factory set.

5Pe

wwvar

camp

camp DCb camp

camp ComP

Keithley

Mfr.

71450

Part No. Ref.

RP34-2

01121 Rl-0 01121

Rl-12K

79727 R12-5K

01121

Rl-4.7K

01121 Rl-8.2K 01121

Rl-15K

Fig.

21

-28

28 28

0179

MODEL 148

REPLACEABLE PARTS

RESISTORS (Cont'd)

Circuit Desig.

R308 R309 R310

R311 R312 R313 R314 R315

R316 2.5 ka R317 R318 R319

Va he Rating

4.7 kn

lO%, l/2 w lO%, l/2 w lO%, l/2 w

Not Used

10 n

5m

6.8 ko

4.7 kc?

lO%, l/2 w camp lO%, l/2 w lO%, l/2 w lO%, l/2 w camp

l%, l/2 w

10 m

l%, l/2 w

12 kn lO%, l/2 w

2

kn

lO%, l/2 w

R320 2.2 !a l%, 112 w R321

R322 R323 R324 R325

4 ka

Lamp, 3v

4.7 kn 10 kn 10 kn

l%, l/2 w lO%, l/2 w

lO%, l/2 w lO%, l/2 w

TYPO camp

camp camp

wwvar camp

DCb DCb camp

wwvar

DCb DCb

CM-2158

camp camp camp

Keithley

Mfr.

Part No.

01121 Rl-4.7K 01121 Rl-4.7K 01121

Rl-4.7K

01121 Rl-10 80294 RP39-5K

01121 Rl-6.8K

01121 Rl-4.7K 79727 Rl2-2.5K

79727 Rl2-1OK 01121 Rl-12K 80294 RP39-2K 79727 R12-2.2K

79727 R12-4K

CM

PL-37 01121 Rl-4.7K 01121 Rl-1OK 01121 Rl-1OK

Fig. Ref.

28 28 28

28 28 28 28

28 28 28

28

28 28

28 28 28 28

TRANSISTORS

Circuit Desig. TyPe

Mfr. Desig.

Mfr.

Refer to page 51 for lower designations.

Q17NPN, Case TO-106 2N5134 07263 Q18NPN, Case TO-106 2N5134 07263 Q19 2N1605 93332 Q20 2N1381 01295

Q21 2N1381 01295 Q22 2N1381 01295 923 2N1381 01295 Q24 2N1381 01295 425 2N1381 01295

Refer to page 53 for higher designations.

MODEL 1481 REPLACEABLE PARTS LIST

Description

Plug Assembly. Cable Assembly, 48 inches

.Copper Alligator Clips (2) (Mfg.

Mfr.

80164 80164

76545

No. 6005)

Keithley Part No.

Fig. Ret.

TG-65 29 TG-65 29 TG-22 29 TG-8 29

TG-8 29

TG-8 29 TG-8 >

with HS-2

29 TG-8 29 TG-8 29

Keithley Part No.

CS-132

14731B

AC-9

0179

55

REPLACEABLE PARTS MODEL 148

MODEL 1482 REPLACEABLE PARTS LIST

Mfg.

Description

Plug Assembly 80164 CS-132 Cable Assembly, 10 feet

MODELS 1483, 1484 REPLACEABLE PARTS LIST

Mfg.

Description

Crimp Tool for Copper lugs 1 #8 Nylon Screws 50 #8 Nylon Hex Nuts 50 Co~oer Bolt-on Lugs 100 CoKper Spade LugsCopper Hook Lugs Copper Splice Tubes

Low-Thermal Cadmium-Tin Solder

Copper Alligator Clips (Mfg.

No. 6005) Shielded Cable Insulated #20 Copper Wire

Non-metalic Abrasive

Quantity

100 100 100

10 feet

10

10 feet

100 feet

3 pads

Code Part No. Kit Model

80164 80164 80164 80164 80164 80

164

80164 80164

76545

80164 80164 80164

Code

80164

Keithley

TL-1

-mm m-m

17340A 17339A 1733bA 17338A

--AC-9

SC-5

ws-1

17774A

Keithley Part No.

14731B

Used on

1483 1483, 1484 1483, 1484

1483, 1484 1483, 1484 1483, 1484 1483, 1484 1483, 1484

1483, 1484 1483, 1484 1483, 1484 1483, 1484

01121 Allen-Bradley Corp.

Milwaukee, Wis.

05397 Kemet Co.

Cleveland, Ohio

I

01295 Texas Instruments, Inc.

Semi-Conductor Components Div.

Dallas, Texas Cleveland, Ohio

01686 RCL Electronics, Inc.

Riverside,, N. 3.

02660 Amphenol-Borg Electronics Corp.

Broadview, Chicago, Illinois

02735 RCA Semiconductor 6 Materials Div.

of Radio Cqrp. of America

Somerville, N. J.

04713

TABLE 14 (Sheet 1). Code List of Suggested Manufacturers. (Based on Federal

supply Code for Manufacturers, Cataloging Handbook H4-1.)

MDtoro1a,

Semiconductor Products Division Phoenix, Arizona

Inc.

08804 Lamp Metals and Component

Dept. G. E. Co.

09052 Gulton Industries, Inc.

Alkaline Battery Division

Metuchen, N. J.

12673 Wesco Division of

Atlee Corp.

Greenfield, Mass.

12954 Dickson Electronics Corp.

Scottsdale, Ariz.

15909 Daven Co.

Livingston, N. J.

I

56

0972

I

1

I I

I I I I I I

I

‘2

c

SERVICE FORM

Model No.

Name Company Address

City

List all control settings and describe problem.

Show a block diagram of your measurement system including all instruments connected (whether power is turned on or not). Also describe signal source.

Serial No.

State

P.O. No.

Phone

(Attach additional sheets as necessary.)

Date

Zip

Where is the measurement being performed? (facton/, controlled laboraton/, out-of-doors, etc.)--_ What power line voltage is used?

Frequency?

Variation?

Any additional information. (If special modifications have been made by the user, please describe below.)

*Be sure to include your name and phone number on this service form.

OF. Rel. Humidity?

Ambient Temperature?

Variation?

OF.

Other?

Keithley 148 Service manual

Specifications and Main Features

Frequently Asked Questions

User Manual