Elenco Electronics M-2665K Assembly And Instruction Manual

Elenco™ Electronics, Inc.

150 W. Carpenter Avenue

Wheeling, IL 60090

[phone]

http://www.elenco.com

e-mail: [e-mail]

DIGITAL MULTIMETER KIT

MODEL M-2665K

WIDE RANGE DIGITAL MULTIMETER WITH

CAPACITANCE AND TRANSISTOR TESTING FEATURES

Assembly and Instruction Manual

Elenco™ Electronics, Inc.

Copyright © 1991 Elenco™ Electronics, Inc. Revised 2002 REV-P 753005

-1-

INTRODUCTION

Range

Switches

Current
Shunts

AC

Converter

Ohms

Converter

Voltage
Divider

Function
Switches

A/D

Converter

and

Display

Driver

Display

Decimal

Point

DC
Analog
Data

V

Ω

VAC

VAC/mA AC

mA

mA

Ω

mA

COMM

V/Ω

V

Figure 1 Simplified Block Diagram

THEORY OF OPERATION

A block diagram of the M-2665K is shown in Figure 1.
Operation centers around a custom LSI chip. This IC
contains a dual slope A/D converter display latches
decoder and the display driver. A block diagram of
the IC functions is shown in Figure 6. The input
voltage, current or ohm signals are conditioned by the
function and selector switches to produce and output
DC voltage between 0 and +199mV. If the input

signal if 100VDC, it is reduced to 100mV DC by
selecting a 1000:1 divider. Should the input be
100VDC, then after the divider it is processed by the
AC converter to produce 100mVDC. If current is to be
read, it is converted to a DC voltage via internal shunt
resistors. For resistance measurements, an internal
voltage source supplies the necessary 0-199mV
voltage to be fed to the IC input.

The input of the 7106 IC is fed to an A/D (analog to
digital) converter. Here the DC voltage amplitude is
changed into a digital format. The resulting signals
are processed in the decoders to light the appropriate
LCD segment.

Timing for the overall operation of the A/D converter
is derived from an external oscillator whose
frequency is selected to be 40kHz. In the IC, this

frequency is divided by four before it clocks the
decade counters. It is further divided to form the
three convert-cycle phases. The final readout is
clocked at about three readings per second.

Digitized measurements data is presented to the
display as four decoded digits (seven segments) plus
polarity. Decimal point position on the display is
determined by the selector switch setting.

Assembly of your M-2665K Digital Multimeter Kit will
prove to be an exciting project and give much
satisfaction and personal achievement. If you have
experience in soldering and wiring technique, you
should have no problems. For the beginner, care
must be given to identifying the proper components
and in good soldering habits. Above all, take your
time and follow the easy step-by-step instructions.
Remember, “An ounce of prevention is worth a
pound of cure”.

The meter kit has been divided into a number of
sections to make the assembly easy and avoid
major problems with the meter operation.

Section A - Meter display circuit assembly.

Section B - DC voltage and current circuit

assembly.

Section C - AC voltage and current circuit

assembly.

Section D - Resistance circuit assembly.

Section E - Capacitance and transistor testing

circuit assembly.

Section F - Final assembly.

1. The function of the A/D converter is to . . .

A. convert digital to analog.

B. divide analog signal by 2.

C. convert analog to digital.

D. convert AC to DC.

2. What type of divider network is used for voltage
measurements?

A. Divide by 20.

B. Capacitance.

C. Divide by 5.

D. Resistor.

3. When the AC voltage is measured, it is first . . .

A. divided down by 2.

B. converted to DC.

C. coupled to a halfwave rectifier.

D. low voltage.

4. When measuring current, the shunt resistors
convert the current to . . .

A. +0.190 to –0.190.

B. –1.199 to +1.199.

C. –0.099 to +0.099.

D. –199 to +0.199.

5. Which IC drives the LCD?

A. 358.

B. LM324.

C. 7106R.

D. 1N5232.

6. Resistance measurements are made by . . .

A. comparing voltage drops in the unknown

resistor and a reference resistor.

B. measuring the current in the unknown

resistor.

C. measuring the current in the reference

resistor.

D. equalizing the voltage drop in the unknown

and reference resistor.

7. Measurement cycles performed by the A/D
converter can be divided into what types of time
periods?

A. Long, short.

B. Auto zero, integrate, read.

C. Zero, read, interphase.

D. Autozero, read, cycle phase.

8. A resistor with band colors green-black-green­brown-green is what value?

A. 50.5kΩ +

5%.

B. 5.15kΩ +

10%.

C. 5.05kΩ +

.5%.

D. 5.05kΩ +

1%.

9. When checking a transistor, the selector knob
should be in the . . .

A. farad position.

B. ohm position.

C. diode position.

D. h

FE position.

10. Where do the leads need to be on the meter

when measuring 450mA?

A. A20, COM.

B. V, COM.

C. A, A20.

D. A, COM.

-34-

QUIZ

Answers: 1. C, 2. D, 3. B, 4. B, 5.C, 6. A, 7. B, 8. C, 9. D, 10.A

During autozero, a ground reference is applied as an
input to the A/D converter. Under ideal conditions the
output of the comparator would also go to zero.
However, input-offset-voltage errors accumulate in the
amplifier loop, and appear at the comparator output as
an error voltage. This error is impressed across the AZ
capacitor where it is stored for the remainder of the
measurement cycle. The stored level is used to provide
offset voltage correction during the integrate and read
periods.

The integrate period begins at the end of the autozero
period. As the per iod begins, the AZ switch opens and
the INTEG switch closes. This applies the unknown
input voltage to the input of the A/D converter. The
voltage is buffered and passed on to the unknown input
voltage to the input of the A/D converter. The voltage is
buffered and passed on to the integrator to determine
the charge rate (slope) on the INTEG capacitor. At the
end of the fixed integrate period, the capacitor is
charged to a level proportional to the unknown input
voltage. This voltage is translated to a digital indication

by discharging the capacitor at a fixed rate during the
read period, and counting the number of clock pulses
that occur before it returns to the original autozero
level.

As the read period begins, the INTEG switch opens and
the read switch closes. This applies a known reference
voltage to the input of the A/D converter. The polarity
of this voltage is automatically selected to be opposite
that of unknown input voltage, thus causing the INTEG
capacitor to discharge as fixed rate (slope). When the
charge is equal to the initial starting point (autozero
level), the read period is ended. Since the discharge
slope is fixed during the read period, the time required
is proportional to the unknown input voltage.
The autozero period and thus a new measurement
cycle begins at the end of the read period. At the same
time, the counter is released for operation by
transferring its contents (previous measurement value)
to a series of latches. This stored stat is then decoded
and buffered before being used for driving the LCD
display.

-2-

AZ

READ

+REF

(FLYING

CAPACITOR)

UNKNOWN

INPUT

VOLTAGE+

INTEG

INTEG

AZ

AZ

READ AZ

INTEG.

TO
DIGITAL
CONTROL
LOGIC

COUNTER OUTPUT

+.20

.15

.10

.05

0

0

10,000

1000500

0

166.7mS

1500

2000

Figure 2 Dual Slope A/D Converter

AZ

COMPARATOR

INTEGRATOR

BUFFER

AMP

EXTERNAL

INPUTS

A/D CONVERTER

A simplified circuit diagram of the analog portion of
the A/D converter is shown in Figure 2. Each of the
switches shown represent analog gates which are
operated by the digital section of the A/D converter.
Basic timing for switch operation is keyed by an
external oscillator. The conversion process is
continuously repeated. A complete cycle is shown
in Figure 2.

Any given measurement cycle performed by the A/D

converter can be divided into three consecutive time
periods: autozero (AZ), integrate (INTEG) and read.
Both autozero and integrate are fixed time periods.
A counter determines the length of both time
periods by providing an overflow at the end of every
1,000 clock pulses. The read period is a variable
time, which is proportional to the unknown input
voltage. The value of the voltage is determined by
counting the number of clock pulses that occur
during the read period.

SCHEMATIC DIAGRAM

-33-

-3-

VOLTAGE MEASUREMENT

Figure 3 Simplified Voltage Measurement Diagram

Figure 4 Simplified Current Measurement Diagram

200mV

Volts

9M

900k

90k

9k

1k

Common

1kV

200V

20V

2V

AC to DC
Converter

AC

DC

Low Pass

Filter

100mV

Ref

7106R

200µ

A

900

2mA

20mA

200mA

20A

100

9Ω

1Ω

Shunt

.01Ω

COM

20A

20A

200mA

20mA

200µA

2mA

AC - DC

Converter

AC

DC

Low
Pass
Filter

100mV

Ref

7106R

Figure 3 shows a simplified diagram of the voltage
measurement function.
The input divider resistors add up 10MΩ with each
step being a division of 10. The divider output
should be withing –0.199 to +0.199V or the overload

indicator will function. If the AC function is selected,
the divider output is AC coupled to a full wave
rectifier and the DC output is calibrated to equal the
rms level of the AC input.

Figure 4 shows a simplified diagram of the current
measurement positions.
Internal shunt resistors convert the current to
between –0.199 to +0.199V which is then

processed in the 7106 IC to light the appropriate
LCD segments. If the current is AC in nature, the
AC converter changes it to the equivalent DC value.

CURRENT MEASUREMENT

4. OPERATION MAINTENANCE

4-1 Battery and Fuse Replacement

-32-

This marking adjacent to another marking or a
terminal operating device indicates that the
operator must refer to an explanation in the
operating instructions to avoid damage to the
equipment and/or to avoid personal injury.

This WARNING sign denotes a hazard. It calls
attention to a procedure, practice or the like, which
if not correctly performed or adhered to, could result
in personal injury.

This CAUTION sign denotes a hazard. It calls
attention to a procedure, practice or the like, which
if not correctly adhered to, could result in damage to
or destruction of part or all of the instrument.

This marking advises the user that the terminal(s)
so marked must not be connected to a circuit point
at which the voltage, with respect to earth ground,
exceeds (in this case) 500 volts.

This symbol adjacent to one or more terminals
identifies them as being associated with ranges that
may in normal use be subjected to particularly
hazardous voltages. For maximum safety, the
instrument and its test leads should not be handled
when these terminals are energized.

5. SAFETY SYMBOLS

CAUTION

BEFORE ATTEMPTING BATTERY REMOVAL OR
REPLACEMENT, DISCONNECT THE TEST
LEADS FROM ANY ENERGIZED CIRCUITS TO
AVOID SHOCK HAZARD.

The fuse rarely needs replacement and blow almost
always as a result of operator error. To replace the
battery and fuse (2A/250V), remove the two screws
in the bottom of the case. Simply remove the old
battery or fuse and replace with a new one.

Be sure to observe the polarity when replacing the
battery.

4-2 Calibration Procedure

It is normally not necessary to recalibrate for long
intervals. If needed, adjustment should be done
with highly accurate standards (setter than 0.1%
accuracy).

Remove the two phillips head screws. Carefully
remove the plastic back cover. With the instrument
operating and set to the 200mV DC range (20µF
capacitance range), apply 190mV DC (10µF) from
an accurate source. With a small screwdriver
inserted into the semi-fixed resistor VR1 (VR2:
Capacitance), carefully turn the variable resistor
until the reading reads 190mV (10µF).

NOTE: Be sure to proceed basic calibration by DC
range first prior to capacitance.

WARNING

CAUTION

500V max.

!

-4-

RESISTANCE MEASUREMENTS

Figure 5 shows a simplified diagram of the resistance measurement function.

Figure 5 Simplified Resistance Measurement Diagram

External
Resistor

100

900

90k

900k

9M

9k

2k

200

20k

200k

2M

20M

Voltage
Source

Reference

Voltage

Low

Pass

Filter

7106R

DCΩ

AC CAP

A simple series circuit is formed by the voltage
source, a reference resistor from the voltage divider
(selected by range switches), and the external
unknown resistor. The ratio of the two resistors is
equal to the ratio of their respective voltage drops.
Therefore, since the value of one resistor is known,
the value of the second can be determined by using
the voltage drop across the known resistor as a
reference. This deter mination is made directly by
the A/D converter.

Overall operation of the A/D converter during a
resistance measurement is basically as described
earlier in this section, with one exception. The
reference voltage present during a voltage
measurement is replaced by the voltage drop
across the reference resistor. This allows the
voltage across the unknown resistor to be read
during the read period. As before, the length of the
read period is a direct indication of the value of the
unknown.

-31-

(D) Diode Test

1. Set the selector switch to the “Ohm” position.

2. Connect the red test lead to “V/Ω” input jack and
the black one to the “COM” jack.

3. Set the range selector knob to the “ ”
position.

4. If the semiconductor junction being measured is
connected to the circuit, turn off the power to the
circuit being tested and discharge all of the
capacitors.

5. Connect the test leads to the device and read
forward value on the digital display.

6. If the digital reads overrange (1), reverse the
lead connections.

The placement of the test leads when the
forward reading is displayed indicates the
orientation of the diode.

The red lead is positive and the black lead is
negative.

If overrange (1) is displayed with both lead
connections, the junction is open.

(E) Transistor h

FE

Measurement

1. Set the selector switch to “DC”.

2. The transistor must be out of circuit. Set the
rotary/function switch to the h

FE position.

3. Plug the emitter, base and collector leads of the
transistor into the correct holes in either the NPN
of the PNP transistor test socket, whichever is
appropriate for the transistor you are checking.

4. Read the h

FE (beta or DC current gain) on the

display.

(F) Capacitance Measurement

1. Set the range selector knob to the “FARAD”
position.

2. Set the range selector knob to the desired
capacitance position.

3. Short the leads of the capacitor to be tested
together to insure that there is no charge on the
capacitor.

4. Insert the capacitor leads into the capacitor test
socket. Note that there are two groups of holes.
One lead must be inserted into one of group one,
and the other lead must be inserted into one of
the holes of group two.

5. Read the capacitance value on the digital
display.

-5-

Figure 6 7106R Functions

a

b

a

b

c

d

e

f

g

TYPICAL SEGMENT OUTPUT

0.5mA

2mA

V+

Segment

Output

Internal Digital Ground

LCD PHASE DRIVER

LATCH

7 Segment

Decode

7 Segment

Decode

7 Segment

Decode

Thousand

Hundreds

Tens Units

*

CLOCK

To Switch Drivers

From Comparator Output

-4

LOGIC CONTROL

Internal Digital Ground

200

BACKPLANE

20

V+

TEST

V

500Ω

4

15

6.2V

1V

* Three inverters.

One inverter shown for clarity.

1

2

3

OSC 1

OSC 2

OSC 3

DIGITAL SECTION

ANALOG SECTION of 7106R

C

REF

R

INT

C

AZ

C

INT

INT

C

REF

+

REF HI

REF LO

C

REF

BUFFER

V+

14

75 6

8

13

12

40

AUTO
ZERO

+

A-Z &

Z1

A-Z &
Z1

A-Z

DE (+)

DE (+)

DE (-)

DE (-)

IN HI

COMMON

IN LO

9

10

INT

10µA

V+

11

INT

+

+

+

2.8V

A-Z & DE(+

)

& Z1

15

V

Z1

6.2V

A-Z

COMPARATOR

ZERO
CROSSING
DETECTOR

POLARITY
FLIP/FLOP

TO
DIGITAL
SECTION

INTEGRATOR

7106R Pin Connections

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

40

39

38

37

36

35

34

33

32

31

30

29

28

27

26

25

24

23

22

21

OSC 1

OSC 2

OSC 3

TEST

REF HI

REF LO

+ REF CAP

– REF CAP

COMMON

INPUT HI

INPUT LO

AUTO-ZERO

BUFFER

INTEGRATOR

(–) SUPPLY

G (TENS)

C (100’s)

A (100’s)

G (100’s)

BACKPLANE

(7106R)

POLARITY

(MINUS)

AB (1000)

E (100’s)

F (100’s)

B (100’s)

D (100’s)

E (TENS)

F (TENS)

A (TENS)

B (TENS)

C (TENS)

D (TENS)

E (UNITS)

G (UNITS)

F (UNITS)

A (UNITS)

B (UNITS)

C (UNITS)

D (UNITS)

(+) SUPPLY

Pin Configuration

7106R

a

b

c

d

e

f

g

a

b

c

d

e

f

g

-30-

(A) DC/AC Voltage Measurement

1. Set the selector switch to “DC” or “AC”.

2. Connect the red test lead to “V/Ω” input jack and
the black one to the “COM” jack.

3. Set the range selector knob to the desired volt
position. If the magnitude of the voltage is not
known, set the range selector knob to the
highest range and reduce until a satisfactory
reading is obtained.

4. Connect the test leads to the device or circuit
being measured.

5. Tur n on the power to the device or circuit being
measured. The voltage value will appear on the
digital display along with the voltage polarity.

6. Tur n off the power to the device or circuit being
tested and discharge all of the capacitors prior to
disconnecting the test leads.

(B) DC/AC Current Measurement

1. Set the selector switch to “DC” or “AC”.

2. Connect the red test lead to the “A” input jack for
current measurement up to 200mA, and the
black one to “COM”.

3. Set the range selector knob to the desired “Amp”
current position.

If the magnitude of current is not known, set the
rotary/function switch to the highest range and
reduce until a satisfactory reading is obtained.

4. Open the circuit to be measured, and connect
the test leads in series with the load in which
current is to be measured.

5. Read the current value on the digital display.

6. Tur n off all power to the circuit being tested and
discharge all of the capacitor prior to
disconnecting the test lead.

7. To measure in the 20A range, use the “20A” jack
as the input jack. Be sure to measure within 10
seconds to avoid high-current hazard.

(C) Resistance Measurement

1. Set the selector switch to the “Ohm” position.

2. Connect red test lead to the “V/Ω” input jack and
the black one to “COM”.

3. Set the range selector knob to desired “Ohm”
position.

4. If the resistance being measured is connected to
a circuit, turn off the power to the circuit being
tested and discharge all capacitors.

5. Connect the test leads to the circuit being
measured. When measuring high resistance, be
sure not to contact adjacent point even if
insulated, because some insulators have a
relatively low insulation resistance, causing the
measured resistance to be lower than the actual
resistance.

6. Read resistance value on digital display.

3-3 Method of Measurement

-6-

ASSEMBLY

The meter kit has been divided into a number of
sections to make the assembly easy and avoid
major problems with the meter operation.

OPEN ONLY THOSE COMPONENT BAGS THAT
ARE CALLED FOR IN YOUR ASSEMBLY
PROCEDURE. DO NOT OPEN ANY OTHER
BAGS.

Do not build more than one section of your meter at
a time. Your instructor must approve the proper
operation of the section you have built before you
proceed to the next section. This procedure will
minimize the problems you may have at the
completion of the project.

Your kit program is divided into Sections “A – F”.
The small parts bags will be marked accordingly.
The sections are listed below.

Section A - Meter display circuit assembly.

Section B - DC voltage and current circuit

assembly.

Section C - AC voltage and current circuit

assembly.

Section D - Resistance circuit assembly.

Section E - Capacitance and transistor testing

circuit assembly.

Section F - Final assembly.

IMPORTANT CONSTRUCTION NOTES

1. Wash your hands with soap and water before you

assemble this kit. The high impedance areas on
the circuit board can be contaminated by salt
and oil from your skin. If these areas become
contaminated, your completed multimeter may
not meet the listed specifications. Handle the
circuit board only by its edges.

2. Avoid any excessive accumulation of resin build-

up whenever you solder a connection.

3. Take your time assembling the circuit board.

Work at a slow pace. Remember that accuracy
is far more important than speed.

4. When you perform the steps in assembly, identify

each respective component before you install it.
Then position it over its outline on the top legend
side of the PC board, unless otherwise indicated.

5. Check for the proper polarity of ICs, diodes,

electrolytic capacitors, battery snap and LCD.

Transistor hFE

Range Test Condition

NPN 10mA 2.8V
PNP 10mA 2.8V

Diode Test

Measures forward resistance of a semiconductor junction in k Ohm at max. test current of 1.5mA.

3. OPERATION

3-1 Preparation and caution before measurement

-29-

LCD Display

Range Selector Knob

Capacitor Input Socket

20A Input Jack

(200mA Max) A input Jack

Selector Switch

hFE Input Socket

Volt Ohm Input Jack

Common Input Jack

1. If the function must be switched during a
measurement, always remove the test leads
from the circuit being measured.

2. If the unit is used near noise generating
equipment, be aware that the display may
become unstable or indicate large errors.

3. Avoid using the unit in places with rapid
temperature variations.

4. In order to prevent damage or injury to the unit,
never fail to keep the maximum tolerable voltage
and current, especially for the 20A current range.

5. Carefully inspect the test lead. If damaged,
discard and replace.

3-2 Panel Description

-7-

Introduction

The most important factor in assembling your M-2665K Digital Multimeter Kit is good soldering techniques.
Using the proper soldering iron is of prime importance. A small pencil type soldering iron of 25 - 40 watts is
recommended. The tip of the iron must be kept clean at all times and well tinned.

Safety Procedures

• Wear eye protection when soldering.

•

Locate soldering iron in an area where you do not have to go around it or reach over it.

• Do not hold solder in your mouth. Solder contains lead and is a toxic substance. Wash your hands
thoroughly after handling solder.

• Be sure that there is adequate ventilation present.

Assemble Components

In all of the following assembly steps, the components must be installed on the top side of the PC board unless
otherwise indicated. The top legend shows where each component goes. The leads pass through the
corresponding holes in the board and are soldered on the foil side.

Use only rosin core solder of 63/37 alloy.

DO NOT USE ACID CORE SOLDER!

CONSTRUCTION

Solder

Soldering Iron

Foil

Solder

Soldering Iron

Foil

Component Lead

Soldering Iron

Circuit Board

Foil

Rosin

Soldering iron positioned
incorrectly.

Solder

Gap

Component Lead

Solder

Soldering Iron

Drag

Foil

1. Solder all components from

the copper foil side only.
Push the soldering iron tip
against both the lead and
the circuit board foil.

2. Apply a small amount of

solder to the iron tip. This
allows the heat to leave the
iron and onto the foil.
Immediately apply solder to
the opposite side of the
connection, away from the
iron. Allow the heated
component and the circuit
foil to melt the solder.

1. Insufficient heat - the
solder will not flow onto the
lead as shown.

3. Allow the solder to flow
around the connection.
Then, remove the solder
and the iron and let the
connection cool. The
solder should have flowed
smoothly and not lump
around the wire lead.

4.

Here is what a good solder
connection looks like.

2. Insufficient solder - let the
solder flow over the
connection until it is
covered. Use just enough
solder to cover the
connection.

3. Excessive solder - could
make connections that you
did not intend to between
adjacent foil areas or
terminals.

4. Solder bridges - occur
when solder runs between
circuit paths and creates a
short circuit. This is usually
caused by using too much
solder. To correct this,
simply drag your soldering
iron across the solder
bridge as shown.

What Good Soldering Looks Like

A good solder connection should be bright, shiny,
smooth, and uniformly flowed over all surfaces.

Types of Poor Soldering Connections

-28-

AC Voltage

Range Resolution Accuracy Maximum Input

200mV 100µV+

1.2% of rdg + 2dgt

2V 1mV +

1.2% of rdg + 2dgt

20V 10mV +

1.2% of rdg + 2dgt AC 750V maximum 50Hz - 400Hz

200V 100mV +

1.2% of rdg + 2dgt

750V 1V +

1.2% of rdg + 2dgt

Resistance

Range Resolution Accuracy Test Current Input Protection

200Ω 0.1Ω +

0.8% of rdg +

2dgt

2kΩ 1Ω +

0.8% of rdg +

2dgt

20kΩ 10Ω +

0.8% of rdg + 2dgt Approximately Protected By

200kΩ 100Ω +

0.8% of rdg + 2dgt 1.2mA PTC

2MΩ 1kΩ +

1.0% of rdg + 3dgt

20MΩ 10kΩ +

3.0% of rdg + 4dgt

Maximum open circuit voltage: 2.8V

DC Current

Range Resolution Accuracy Protection

200µA 100nA +

0.5% of rdg + 2dgt

2mA 1µA+

0.5% of rdg + 2dgt Protected by

20mA 10µA+

0.5% of rdg + 2dgt 250V/2A Fuse

200mA 100µA+

0.5% of rdg + 2dgt

20A 10mA +

1.0% of rdg + 3dgt

AC Current

Range Resolution Accuracy Protection

200µA 100nA +

1.2% of rdg + 3dgt

2mA 1µA+

1.2% of rdg + 3dgt Protected by

20mA 10µA+

1.2% of rdg + 3dgt 250V/2A Fuse

200mA 100µA+

1.2% of rdg + 3dgt

20A 10mA +

3.0% of rdg + 3dgt

Capacitance

Range Resolution Accuracy Protection

2nF 1pF +

3.0% of rdg + 3dgt

2nF 10pF +

3.0% of rdg + 3dgt

200nF 100pF +

3.0% of rdg + 3dgt Test frequency 400Hz+3.0% Test Voltage 120mV

2µF 1nF +

3.0% of rdg + 3dgt

20µF 10nF +

3.0% of rdg + 3dgt

PART IDENTIFICATION CARDS

To help identify the resistors and diodes used in the construction of your digital
multimeter we have mounted the diodes and resistors of each section onto a card.
The card will help you find the diodes and resistors quickly. THE PARTS WILL NOT
NECESSARILY BE LISTED IN THE ORDER SHOWN IN THE PARTS LIST SECTION
OR IN THE ASSEMBLY PROCEDURE.

When you are ready to assemble the meter kit, follow the procedure shown. For an
example refer to page 11 for assembly of Section “A”. The first resistor called for is
R-20, 110kΩ resistor (brown-brown-yellow-gold). Locate it on the card ( ), verify that
it is the correct value. Some resistors may be mounted backwards on the card so you
must be certain that you are reading the resistors correctly. When the correct value
has been established, only then will you mount it into its correct position on the PC
board.

IDENTIFYING RESISTOR VALUES

Use the following information as a guide in properly identifying the value of resistors.

SECTION A

5 Bands

1 2

Multiplier

Tolerance

3

4 Bands

1

2

Multiplier

Tolerance

-8-

EXAMPLE

IDENTIFYING CAPACITOR VALUES

Capacitors will be identified by their capacitance value in pF (picofarads), nF (nanofarads), or µF (microfarads). Most
capacitors will have their actual value printed on them. Some capacitors may have their value printed in the following
manner. The maximum operating voltage may also be printed on the capacitor.

Second Digit

First Digit

Multiplier

Tolerance*

For the No.01234589

Multiply By 1 10 100 1k 10k 100k .01 0.1

Multiplier

Note: The letter “R” may be used at times to
signify a decimal point; as in 3R3 = 3.3

10µF 16V

103K

100V

The letter M indicates a tolerance of +

20%

The letter K indicates a tolerance of +

10%

The letter J indicates a tolerance of +5%

Maximum Working Voltage

The value is 10 x 1,000 =
10,000pF or .01µF 100V

*

-27-

1. FEATURES

• Wide measuring ranges: 34 ranges for AC/DC Voltage and Current, Resistance, Capacitance, TR hFE,
Diode Test.

• 10MΩ Input Impedance

• Big LCD for easy reading

• Tilt Stand

2. SPECIFICATIONS

2-1 General Specifications

Display 3 1/2 LCD 0.95” height, maximum reading of 1999.

Polarity Automatic “–” sign for negative polarity.

Overrange Indication Highest digit of “1” or “–1” is displayed.

Low Battery Indication “BAT” lettering on the LCD readout.

Operating Temperature 0

O

C to 50OC.
less than 80% relative humidity up to 35OC.
less than 70% relative humidity from 35OC to 50OC.

Storage Temperature –15

O

C to 50OC

Temperature Coefficient 0

O

C to 18OC and 28OC to 50OC.
less than 0.1 x applicable accuracy specification per degree C.

Power 9V alkaline or carbon zinc battery (NEDA 1604).

Battery Life (typical) 100 hours with carbon zinc cells.

200 hours with alkaline cells.

Dimensions 3.47” (88mm) (W) x 7.52” (191mm) (L) x 1.42” (36mm) (H).

Weight Approximately 10.4oz. (300g.)

Accessories Safety Test Lead 1 pair

2-2 Measurement Ranges (Accuracy: 1 year 18OC to 28OC)

DC Voltage

Range Resolution Accuracy Maximum Input

200mV 100µV+

0.5% of rdg + 2dgt

2V 1mV +

0.5% of rdg + 2dgt

20V 10mV +

0.5% of rdg + 2dgt DC 1000V or peak AC

200V 100mV +

0.5% of rdg + 2dgt

1000V 1V +

0.5% of rdg + 2dgt

Normal Mode Rejection Ratio: Greater than 46dB at 50Hz 60Hz (1k unbalance)

-9-

RESISTOR READING EXERCISE

(1) yellow-black-black-black-brown

(3) brown-red-violet-red-brown

(5) brown-black-black-black-brown

(7) white-black-black-yellow-green

(9) brown-black-black-orange-green

(11) gray-white-black-black-brown

(2) white-black-black-red-green

(4) green-black-green-brown-green

(6) brown-green-gray-orange-brown

(8) white-black-black-silver-green

(10) orange-white-red-red-brown

(12) brown-brown-black-red-brown

Answers to Resistor Reading Exercise: 1) 400Ω+1%; 2) 90kΩ+.5%; 3) 12.7kΩ+1%; 4) 5.05kΩ+.5%; 5) 100Ω+1%;

6) 158kΩ+

1%; 7) 9MΩ+.5%; 8) 9Ω+.5%;9) 100kΩ+.5%; 10) 39.2kΩ+1%; 11) 890Ω+1%; 12) 11kΩ+1%;

Before starting assembly of your digital multimeter
project, you should be thoroughly familiar with the 5
band color code system. Many of the resistor
values will be identified by color bands and it is easy
to mistake their value if you read the colors

incorrectly or read the value from the wrong end.
Do the following exercise in resistor values. Place
your answer in the box beneath the resistor.
Answers are on the bottom of this page.

Table 1

-26-

REINSTALLATION OF THE RANGE SELECTOR KNOB

If you removed the range selector knob for troubleshooting,
then follow the instructions below to reinstall it.

Place the PC board over the range selector knob and
fasten the knob to the PC board with a M2.3 x 8 screw.
CAUTION: Do not overtighten the screw. The knob
should be snug, but not loose. Turn back the M2.3 x 8
screw 1/2 turn. Slip the two shims under the knob (see
Figure L). If they do not slip in, turn back the screw
another 1/4 turn. Tighten the screw just enough so that
the shims can be pulled out. You should now have the
proper tension to hold the knob and contacts in place and
rotate the knob to the desired positions.

USING THE DIGITAL MULTIMETER

MEASURED RANGE SETTING

RESISTANCE 200Ω 2kΩ 20kΩ 200kΩ 2MΩ 20MΩ

00.1 .000 0.00 00.0 .000 0.00

INFINITY 1 . 1. 1 . 1 . 1. 1 .

47Ω 52.1 .052 0.05 00.0 .000 0.00

270Ω 1 . .267 0.26 00.2 .000 0.00

10kΩ 1 . 1. 10.18 10.2 .010 0.01

47kΩ 1 . 1. 1 . 52.7 .052 0.05

470kΩ 1 . 1. 1 . 1 . .472 0.47

2.2MΩ 1 . 1. 1 . 1 . 1. 2.12

SHORT

(LEADS TOUCHING)

*

* RESISTANCE OF TEST LEADS

Table 2

Bottom View of Selector Knob

& Slide Contacts

Slide Contact

Shim

Shim

Figure L

MEASURED

VOLTAGE 200mV 2V 20V 200V 1000V

117VAC 1 . 1. 1 . 117.0 117

100VDC 1 . 1. 1 . 100.0 100

Familiarize yourself with your new digital meter by
taking readings of known resistances and voltages.
You will find that the readings will not be as accurate
on certain ranges for a given measurement. For
example, when measuring a low resistance on a
high range, the reading will show a short 0.00.
When measuring a high resistance on a low range,
the reading will show infinity 1. Likewise, it is
important to use the correct range when measuring
voltages.

Table 1 shows an example of the readouts for
different values of resistance. Table 2 shows an
example of the readouts for 117VAC and 100VDC.
The shaded area indicates the most accurate range.
It must be remembered that the readings will shift
slightly when switching to a different range.

-10-

PARTS LIST - SECTION A

If any parts are missing or damaged, see instructor or bookstore. DO NOT contact your place of purchase as they will not
be able to help you.
Contact Elenco™ Electronics (address/phone/e-mail is at the back of this manual) for additional assistance, if needed.

RESISTORS

Qty. Symbol Description Color Code Part #

1 R24 56kΩ 5% 1/4W green-blue-orange-gold 155600
1 R19 100kΩ 5% 1/4W brown-black-yellow-gold 161000
1 R20 110kΩ 5% 1/4W brown-brown-yellow-gold 161100
6 R16, 17, 18, 21, 22, 23 1MΩ 5% 1/4W brown-black-green-gold 171000

Note: Resistor tolerance (last band) of 5-band resistors may be green instead of brown.

CAPACITORS

Qty. Symbol Value Description Part #

1 C2 100pF (101) Ceramic Capacitor 221017
1C3 .047µF (473) Mylar Capacitor 244717
1C4 .1µF (104) Mylar Capacitor 251017
2 C5, C6 .22µF (224) Mylar Capacitor 252217

SEMICONDUCTORS

Qty. Symbol Value Description Part #

1 ZD 1N5232/1N752 Zener Diode 315232
1 U2 4030/4070 Integrated Circuit 334030
1 U1 7106R Integrated Circuit 337106R

MISCELLANEOUS

SECTION A

Meter Display Circuit

Resistor

PARTS IDENTIFICATION

Capacitor

Ceramic Mylar

Diode

Integrated Circuit

Socket

Liquid Crystal Display (LCD)

*
*

*

Parts installed on PC board already.

Qty. Description Part #

1 Liquid Crystal Display (LCD) 35114A
1 Zebra 500000
1 PC Board 516000A
1 Solder Roll 551135
1 Battery Snap (BAT) 590098
1 Battery 590009
1 LCD Window Plate 621002A
1 Range Selector Knob 622003
1 Bushing 624004

Qty. Description Part #

1 LCD Stopper 629005
1 LCD Housing 629007
2 M2.3 x 6 Screw 642360
1 M2.3 x 8 Screw 642430
1 IC Socket 40-Pin 664040
6 Slide Contact 680016
1 Top Plate (A) 724001A
2 Shims (see page 26) 780006

*

*

Battery Snap

Top Plate (A)

LCD Housing

LCD

LCD Stopper

Zebra

LCD Window
Plate

-25-

Amps Section

1. 200mA scale not working:

A. Check fuse.

B. Measure across (A) terminal and (COM)

terminal for 1Ω (set meter in 200mA).

1. Lower or higher than 1Ω, Check R13.

2. 20mA scale not working:

A. Check fuse.

B. Measure between (A) terminal and

(COM) for 10Ω (set meter in 20mA).

1. Lower or higher than 10Ω, check R12
and R13.

Capacitance Section

1. Place .001µF cap in the socket and check pin 7
and pin 8 of U4 with a scope (meter set to 2N).

Pin 7 370Hz - 400Hz .12Vpp.

Pin 14 370Hz - 400Hz .3Vpp.

A. No signal at pin 14.

1. Check D3, D4 and shorts.

B. No signal at pin 7 but present at pin 1.

1. Check D5 and D6.

hFE Section

1. Check for shorts on socket pins.

2. Measure across B terminal to COM terminal for
251kΩ.

A. Lower or higher than 251kΩ; Check R14

and R15.

Decimal Point Section

1. Displays two decimal points.

A. Shorted output on U2.

2. No decimal points displayed.

A. Check U2 325.

Diode

1. Measure voltage across V OHM and COM
terminal (set in diode mode) = 1.3V.

A. Low voltage, check R26.

Battery Low Indicator

1. Not working.

A. Check ZD1, R19 and U2.

-11-

Mount the capacitors with 1/4” of
space between the body and the
PC board. Bend cap over as
shown.

Figure D

Figure A

Align the notch on the socket (if any) with the notch
marked on the PC board. Solder the socket to the PC
board. Inser t the IC into the socket with the notch as
shown below. Note: If the IC is already inserted into

the socket, do not attempt to pull it out, as this will
damage the IC and socket. Instead, solder the socket
to the PC board with the IC in it.

Figure C

Mount the diodes with the
band in the correct direction
as shown on the top legend.

ASSEMBLE THE FOLLOWING COMPONENTS TO THE PC BOARD

In all of the following steps the components must be installed on the top legend side of the PC board. The
board is turned to solder the component leads on the selector switch side.

Band

Figure B

Lay resistor flat against the
PC board.

U1 - IC Socket 40-pin
U1 - 7106R IC

(see Figure A)

R20 -

110kΩ 5% 1/4W Res.

(brown-brown-yellow-gold)

(see Figure B)

C2 - 100pF (101) Ceramic Cap.

(see Figure D)

R21 - 1MΩ

5% 1/4W

Res.

R22 - 1MΩ

5% 1/4W

Res.

(brown-black-green-gold)

(see Figure B)

C3 - .047µF (473) Mylar Cap.

(see Figure D)

R23 - 1MΩ

5% 1/4W

Res.

(brown-black-green-gold)

(see Figure B)

C4 - .1µF (104) Mylar Cap.

(may be marked 104)

(see Figure D)

R24 - 56kΩ

5% 1/4W

Res.

(green-blue-orange-gold)

(see Figure B)

U2 - 4030 IC or 4070

No IC socket used

Solder the IC to the PC board
with the notch in the direction
shown on the top legend.

C5 - .22µF (224) Mylar Cap
C6 - .22µF (224) Mylar Cap.

(see Figure D)

R16 - 1MΩ 5% 1/4W Res.
R18 - 1MΩ 5% 1/4W Res.
R17 - 1MΩ 5% 1/4W Res.

(brown-black-green-gold)

(see Figure B)

R19 -

100kΩ 5% 1/4W Res.

(brown-black-yellow-gold)

(see Figure B)

ZD - 1N5232 Diode

(see Figure C)

BAT - Battery Snap
Insert both wires through the
hole and mount the red wire to
the (+) hole and the black wire
to the (–) hole. Solder the
wires from the top legend
side.

Notch

Notch

-24-

U1 (7106R) Voltage Test

1. Measure the voltage across pin 40 and pin 15 on
U1 (7106R) for 9V.

A. Check the battery connection.

B. Check for a 9V and GND short.

1. One of the ICs may be bad. Remove
one IC at a time and check voltage
again between pins 40 - 15.

2. Measure the voltage across pin 40 and pin 9 on
U1 for 3V.

A. U1 is defective.

3. Check the Main Oscillator on U1 (7106R) pins 1,
2, 3.

Pin 1

Pin 2

Pin3

4. Measure the voltage across pin 5 and pin 6 on
U1 (7106R) for 70mV - 105mV (reference
voltage).

A. Adjust VR1 so the the junction of R46,

R27 and R28 equal to 100mV.

1. Can’t set to 100mV.
a. VR1 wrong value or defective.
b. R25, R27 and R28 wrong value.

B. Can’t obtain 100mV between pin 5 and

pin 6.

1. Check R21 and R46.

Voltage/OHM Section

1. Measure across V OHM terminal and COM
terminal for 10MΩ (set meter in 200mV) battery
installed.

A. Lower or higher than 10MΩ.

1. Check resistors R1 - R6.

2. LCD readings floating.

A. Measure across the COM terminal to pin

6 on U1 (7106R) for 1MΩ.

1. R22 open or defective.

AC Voltage Section

1. Apply 15VAC to meter and measure pin 1 and pin
7 of U3 (358) to COM terminal with a scope
(meter on 20VAC scale).

Pin 1 to COM 0.44Vpp

A. Check DC/AC switch

B. Check C7, R29 - R32, D7, D8 and U3.

Pin 7 to COM 1.4Vpp

A. Check R33 - R36, D9, D10, C9 and U3.

2. Check pin 10 and pin 11 of U1 (7106R) with a
scope.

Waveform on pin 10 and pin 11.

A. Check C4 and R23.

0.2Vpp

If the meter is not working, perform the U1 (7106R)
Voltage Test first. This test is to verify that the IC
and Reference Voltage are operational. Then

perform the tests that pertain to the Function that is
not working on your meter.

TROUBLESHOOTING GUIDE

Assemble the LCD into the housing with the parts
shown in Figure E. The LCD must be put in with
the notch in the direction shown in Figure E. Peel
off the clear protective film on top of the LCD (see
Figure G), then place the LCD plate into the
housing with the two curved corners on the inside
of the plate in the same direction as the two
curved corners on the housing. Wipe off zebra
edges with a lint-free cloth.

Mount the LCD unit to the PC board. Insert the
two pins on the side shown in Figure E into the
holes on the PC board. Then push the other end
down until it snaps into place.

Screw the LCD housing to the PC board with two
M2.3 x 6 screws as shown in Figure E.

Testing Procedure

Placing the top plate (A) over the knob will assist in
obtaining the correct knob position when doing
tests.

Connect the 9V battery and turn the range selector.
The LCD will display random numbers. As you turn
the knob clockwise, the decimal point will move
also. Check that all of the segments that make up
the certain number are displayed. If the LCD is
working correctly, move the knob to the off position
and remove the battery. If the tests are not working,
check for cold solder joints, part values and if the
LCD is assembled correctly. DO NOT PROCEED

TO SECTION B WITHOUT INSTRUCTOR’S
APPROVAL.

-12-

ASSEMBLE THE LCD

Figure F

Clear Protective Film

Figure E

After the LCD unit is assembled, insert
this side into the PC board first.

LCD Housing

LCD

Notch

LCD Stopper

Zebra - Do not touch edge

PC Board

M2.3 x 6 Screws

Battery

Range

Selector Knob

LCD Window Plate

NOTE: If the range selector switch
becomes hard to turn, then loosen the
M2.3 x 8 screw slightly.

-23-

Testing Procedure SECTION C - AC voltage
and current circuit

Measure an AC voltage with a known accurate
meter. Now measure the voltage with the kit meter.
The meters should be the same voltage.

Connect the kit meter and another meter of known
accuracy in series. Set the meters in the 200mA
position. Construct a circuit for an AC current and
measure the circuit current. Both meters should
have close to the same readings. If the meters do
not agree, check the parts just added. Do not re­adjust VR1 this will change the voltage reading set
in step 1. Check the 200µ - 200mA scales. The 20A
scale requires, a circuit of 1 - 10 amps. If the tests
are not working, check for cold solder joints and part
values. DO NOT PROCEED TO SECTION F

WITHOUT INSTRUCTORS APPROVAL.

Testing Procedure SECTION F

Set the meter in one of the farad scales. Make sure
that SW1 is in the AC/Cap position. Measure a cap
with another meter and then insert the same cap
into the kit meters CX connectors. Adjust VR2 so
that the meter reads the same as the accurate one.
This calibrates capacitance circuit of meter. Using
two or three different value capacitors, check each
scale. Compare the kit meter readings with another
meter. Turn the meter off and remove the battery.

Set the meter in the h

FE scales. Place an NPN

transistor into the socket. Make sure that the
transistor is in correctly. Depending on the type of
transistor, the meter will range from 20 to 550.
Place a PNP transistor into the PNP socket, the
range will also be 20 to 550. If the tests are not
working, check for cold solder joints and part values.

-13-

PARTS LIST - SECTION B

RESISTORS

Qty. Symbol Description Color Code Part #

1 R13 1Ω .5% 1/2W brown-black-gold-green / OR brn-blk-blk-sil-grn 111051
1 R12 9Ω .5% 1/4W white-black-black-silver-green 119050
1 R6 100Ω .5% 1/4W brown-black-black-black-green 131050
1 R5 900Ω .5% 1/4W white-black-black-black-green 139050
1 R28 1.3kΩ 1% 1/4W brown-orange-black-brown-brown 141230
1 R27 2kΩ 1% 1/4W red-black-black-brown-brown 142030
1 R46 5.6kΩ 5% 1/4W green-blue-red-gold 145600
1 R26 8.2kΩ 5% 1/4W gray-red-red-gold 148200
1R4 9kΩ .5% 1/4W white-black-black-brown-green 149050
1 R25 39.2kΩ 1% 1/4W orange-white-red-red-brown 153930
1 R3 90kΩ .5% 1/4W white-black-black-red-green 159050
1 R2 900kΩ .5% 1/4W white-black-black-orange-green 169050
1R1 9MΩ .5% 1/2W white-black-black-yellow-green 179051
1 VR1 200Ω / 220Ω Potentiometer 191320

Note: Some resistors may not have a color coding, but they will have the value imprinted on them.

Note: Resistor tolerance (last band) of 5-band resistors may be green instead of brown.

CAPACITORS

Qty. Symbol Value Description Part #

1C1 22µF Electrolytic (Lytic) 272244

SEMICONDUCTORS

Qty. Symbol Value Description Part #

2 D1, D2 1N4001 or 1N4007 Diode 314001

MISCELLANEOUS

Qty. Symbol Description Part #

1 Shunt Wire M1.6 x 60 100069
1 Fuse 2A 533020
1 SW1 Slide Switch 541104
1 Slide Switch Knob 622004
2 Fuse Holder Clips 663003
4 Input Socket 664000
1 Test Lead Set RWTL14

SECTION B

DC Voltage & Current Circuit

*

* Part installed on PC board already

-22-

Top Case

Figure K

(A)

Top Plates

(B)

Bearings

Springs

Spring

Range Selector Knob

Battery

Spring

Ball

Bearing

Grease

Selector

Knob

Bottom Case

Shield Plate

Battery

Cushion

M3 x 12 Screws

Stand

Figure F

Lytics have a polarity marking on
them indicating the negative lead, the
opposite lead is positive. The PC
board is marked to show the positive
(+) lead position. Mount the capacitor
with the positive (+) lead in the hole
marked on the PC board. Bend the
capacitor over.

R6 - 100Ω .5% 1/4W Res.
(brown-blk-blk-blk-green)

(see Figure E)

R5 - 900Ω .5% 1/4W Res.

(white-blk-blk-blk-green)

(see Figure E)

R4 - 9kΩ .5% 1/4W Res.

(white-blk-blk-brown-green)

(see Figure E)

R3 - 90kΩ 1/4W .5% Res.

(white-blk-blk-red-green)

(see Figure E)

R2 -

900kΩ .5% 1/4W Res.

(white-blk-blk-orange-green)

(see Figure E)

R1 - 9MΩ .5% 1/2W Res.

(white-blk-blk-yellow-green)

(see Figure B)

D1 - 1N4001 Diode
D2 - 1N4001 Diode

(see Figure C)

R12 - 9Ω 1/4W .5% Res.

(white-blk-blk-silver-green)

(see Figure B)

R13 - 1Ω .5% 1/2W Res.
(brown-black-gold-green)

(see Figure B)

Fuse Holder Clips

Fuse 2A
Mount holders with the tab
side as shown on the top
legend then insert fuse.

-14-

ASSEMBLE THE FOLLOWING COMPONENTS TO THE PC BOARD

In all of the following steps the components must be installed on the top legend side of the PC board. The
board is turned to solder the component leads on the selector switch side.

Figure E

Stand resistor on end as
shown with the body
inside the white circle.

White
Circle

R26 -

8.2kΩ 5% 1/4W Res.

(gray-red-red-gold)

(see Figure E)

R25 - 39.2kΩ 1% 1/4W Res.

(orange-white-red-red-brown)

(see Figure E)

C1 - 22µF Lytic Capacitor

(see Figure F)

R27 - 2kΩ 1% 1/4W Res.

(red-blk-blk-brown-brown)

(see Figure E)

R28 -

1.3kΩ 1% 1/4W Res.

(brn-orange-blk-brn-brn)

(see Figure E)

R46 -

5.6kΩ 5% 1/4W Res.

(green-blue-red-gold)

(see Figure E)

VR1 - 200Ω
Potentiometer

Shunt

+

C1

+

Tab

Push into board

up to stops

Solder the spring to the PC board as shown in
Figure Ja.

See Figure K for the following steps.

Peel off the protective backing on the top plates
(A) and (B) and stick them to the top case. Peel
off the protective backing on the battery cushion
and stick it onto the bottom case. (These may be
installed on the case already).

Turn the selector knob screw one full turn out as
shown in the figure.

Place the PC board on a standard piece of paper
(8 1/2” x 11”). Inser t the two springs into the
holes on the range selector knob. Put grease on

top of the springs and then place a ball bearing
on each spring. Press the top case onto the PC
board. Using both hands, slide your fingers
under the paper. Press your thumbs down on the
top case and then flip the board. Be sure to hold
the PC board to the case firmly or the ball
bearings will fall out. Fasten the PC board to the
top case with three M2.3 x 6 screws in the places
shown in Figure J.

Connect the battery and place it in the cavity of
the top case.

Place the bottom case onto the top case. Hold
the two sections together with two M3 x 12
screws.

-21-

FINAL ASSEMBLY

Spring

Pad

Screw Holes

Figure J

Figure Ja

Solder

Spring

-15-

Push the four input sockets into the PC board holes from the selector switch side until they stop (see
Figure G). Turn the board over as shown in Figure Ga and solder the sockets in place from the top legend
side. Apply enough heat to allow the solder to flow around the input sockets (see Figure Gb).

Push on the slide switch knob.

Connect the 9V battery to the meter. Turn the range
selector knob to the 20V position and connect the
test leads (red lead to VΩ and black to COM). Using
another meter of known accuracy, measure a DC
voltage less than 20V (such as a 9 volt battery). You
will calibrate the kit meter by measuring the same
voltage source and adjusting VR1 until the kit meter
reads the same as the accurate meter. When the
two meters agree, the voltage circuit is calibrated.
Turn the range selector knob to the off position.

Current Test

Connect the kit meter and another meter of known
accuracy in series. Set the meters in the 200µA

position. Construct a circuit for a DC current (for
example 9V and a 47kΩ resistor for 190µA) and
measure the circuit. Both meters should have close
to the same readings. If the meters do not agree,
check the parts just added. Do not readjust VR1 for
this will change the voltage reading set in step 1.
Check that 200µA - 200mA scales. The 20A scale
requires a circuit of 1 - 10 amps. If the tests are not
working, check for cold solder joints and part values.
Turn the meter off and remove the battery and test
leads. DO NOT PROCEED TO SECTION C

WITHOUT YOUR INSTRUCTOR’S APPROVAL.

Figure G

Figure Ga

Figure Gb

Top Legend Side

Top Legend Side

Solder

Socket

Sockets

Input

Sockets

Slide Switch

Slide Switch Knob

Testing Procedure

Voltage Test

Figure Gc

9V

– +

47kΩ

-20-

Mount the two 9-pin component sockets to the PC board with the notch at the base of the socket in the
direction shown in Figure I. Solder the sockets in place from the top legend side.

PARTS LIST - SECTION F

Qty. Description Part # Qty. Description Part #

1 Battery Cushion 620001 1 Shield Spring 680008
1 Top Case 623101A 2 Knob Spring 680009
1 Bottom Case w/Stand 623200A 1 Top Plate (B) 724000A
3 Screw M2.3 x 6 642360 1 Shield 780008
2 Screw M3 x 12 642367 1 Grease 790004
2 Bearing 666001

Note: The shield and battery cushion may be installed already.

SECTION F

Final Assembly

Figure I

Component Socket

Component Socket

Notch

Notch

Testing Procedure

Connect the 9V battery and test leads to the meter
(red to VΩ and black to COM). Set the range
selector knob to the diode scale and set SW1 in the
DC Ohm position. Connect a diode to the test leads
with the correct polarity (see figure below). The

meter will range for 100 - 950. If the tests are not
working, check for cold solder joints and part values.
Turn the meter off and remove the battery and test
leads.

DO NOT PROCEED TO SECTION E WITHOUT INSTRUCTOR’S APPROVAL.

COM

VΩ

-16-

PARTS LIST - SECTION C

RESISTORS

Qty. Symbol Description Color Code Part #

1 R31 5.05kΩ .5% 1/4W green-black-green-brown-green 145050
1 R33 5.6kΩ 5% 1/4W green-blue-red-gold 145600
2 R35, 36 5.62kΩ .5% 1/4W green-blue-red-brown-green 145650
1 R29 10kΩ 5% 1/4W brown-black-orange-gold 151000
1 R32 200kΩ 5% 1/4W red-black-yellow-gold 162000
1 R34 390kΩ 5% 1/4W orange-white-yellow-gold 163900
1 R30 2.2MΩ 5% 1/4W red-red-green-gold 172200

Note: Resistor tolerance (last band) of 5-band resistors may be green instead of brown.

CAPACITORS

1C9 .1µF (104) Ceramic 251010
1C7 .1µF (104) Mylar 251017
1C8 22µF Electrolytic (Lytic) 272244

SEMICONDUCTORS

4 D7 - D10 1N4148 Diode 314148
1 U3 358/17358 Integrated Circuit 330358

MISCELLANEOUS

1 U3 IC Socket 8-pin 664008

SECTION C

AC Voltage & Current Circuit

ASSEMBLE THE FOLLOWING COMPONENTS TO THE PC BOARD

D9 - 1N4148 Diode

D10 - 1N4148 Diode

(see Figure H)

R35 - 5.62kΩ .5% 1/4W Res.

R36 - 5.62kΩ .5% 1/4W Res.

(green-blue-red-brn-green)

(see Figure B)

C7 - .1µF (104) Mylar Cap.

R29 - 10kΩ 5% 1/4W Res.

(brown-black-orange-gold)

(see Figure B)

R34 -

390kΩ 5% 1/4W Res.

(orange-white-yellow-gold)

(see Figure E)

R32 -

200kΩ 5% 1/4W Res.

(red-black-yellow-gold)

(see Figure E)

R31 - 5.05kΩ .5% 1/4W Res.

(green-blk-green-brn-green)

(see Figure E)

In all of the following steps the components must be installed on the top legend side

of the PC board. The board is turned to solder the component leads on the
selector switch side.

C9 - .1µF (104) Ceramic Cap.

R33 -

5.6kΩ 5% 1/4W Res.

(green-blue-red-gold)

(see Figure E)

D7 - 1N4148 Diode
D8 - 1N4148 Diode

(see Figure H)

R30 -

2.2MΩ 5% 1/4W Res.

(red-red-green-gold)

(see Figure E)

C8 - 22µF Lytic Capacitor

(see Figure I)

U3 - IC Socket 8-pin
U3 - 358 Integrated Circuit

Align the notch on the socket (if any)
with the notch marked on the PC
board. Solder the socket to the PC
board. Insert the IC into the socket with
the notch as shown below.

Socket

Notch

C8

Figure I

Mount the capacitor with the
negative ( ) lead in the negative
hole and the positive (+) lead in
the positive hole marked on the
PC board. Lay the capacitor flat
against the PC board as shown.

Figure H

Mount the diode with the
band in the direction of the
arrow on the top legend.

-19-

ASSEMBLE THE FOLLOWING COMPONENTS TO THE PC BOARD

In all of the following steps the components must be installed on the top legend side of the PC board. The
board is turned to solder the component leads on the selector switch side.

U4 - IC Socket 14-pin
U4 - 324 Integrated Circuit

Align the notch on the socket (if
any) with the notch marked on
the PC board. Solder the socket
to the PC board. Insert the IC
into the socket with the notch as
shown below.

Notch

R44 - 76.8kΩ 1% 1/4W Res.

(violet-blue-gray-red-brown)

(see Figure E)

R43 - 11kΩ 1% 1/4W Res.

(brown-brown-blk-red-brn)

(see Figure E)

R42 - 39.2kΩ 1% 1/4W Res.

(orange-white-red-red-brn)

(see Figure E)

R14 - 240kΩ 5% 1/4W Res.
R15 - 240kΩ 5% 1/4W Res.

(red-yellow-yellow-gold)

(see Figure B)

C12 - .01µF (103) Mylar Cap.

C13 - .01µF (103) Mylar Cap.

D3 - 1N4001 Diode
D4 - 1N4001 Diode

(see Figure H)

R45 - 158kΩ 1% 1/4W Res.

(brown-grn-gray-orange-brn)

(see Figure E)

D11 - 1N4148 Diode

(see Figure C)

R7 - 98.8Ω 1% 1/4W Res.

(wht-gray-gray-gold-brn)

(see Figure E)

R8 - 900Ω 1% 1/4W Res.

(wht-blk-blk-blk-brn)

(see Figure E)

R9 - 9kΩ 1% 1/4W Res.

(wht-blk-blk-brn-brn)

(see Figure E)

R10 - 90kΩ 1% 1/4W Res.

(wht-blk-blk-red-brn)

(see Figure E)

R11 - 909kΩ 1% 1/4W Res.

(wht-blk-wht-org-brn)

(see Figure E)

VR2 - 200Ω

Potentiometer

D5 - 1N4001 Diode
D6 - 1N4001 Diode

(see Figure H)

R39 - 39.2kΩ 1% 1/4W Res.

(org-wht-red-red-brn)

(see Figure E)

R37 - 150Ω 5% 1/4W Res.

(brn-grn-brn-gold)

(see Figure E)

C11 - .01µF (103) Mylar Cap.

C10 - .01µF (103) Mylar Cap.

R41 - 1.91kΩ 1% 1/4W Res.

(brn-wht-brn-brn-brn)

(see Figure E)

R38 - 10kΩ 1% 1/4W Res.

(brn-blk-blk-red-brn)

(see Figure E)

R40 - 4.12kΩ 1% 1/4W Res.

(yel-brn-red-brn-brn)

(see Figure E)

PARTS LIST - SECTION D

Qty Symbol Description Part #

1 PTC 1kΩ Thermister 190415

ASSEMBLE THE FOLLOWING COMPONENT TO THE PC BOARD

The other components for this section have been installed already.

SECTION D

Resistance Circuit

-17-

Testing Procedure

Connect the 9V battery and test leads to the meter
(red to VΩ and black to COM). Set the range
selector knob to one of the Ohm scales. Make sure
that SW1 is in the DC/Ohm position. Using two or
three different value resistors, check each scale.
Compare the kit meter readings with another meter

of known accuracy. If the tests are not working,
check for cold solder joints, part values, and the
contacts on the selector knob to make sure that they
are intact. Turn the meter off and remove the battery
and test leads.

-18-

PARTS LIST - SECTION E

RESISTORS

Qty. Symbol Description Color Code Part #

1R7 98.8Ω 1% 1/4W white-gray-gray-gold-brown 129830
1 R37 150Ω 5% 1/4W brown-green-brown-gold 131500
1 R8 900Ω 1% 1/4W white-black-black-black-brown 139030
1 R41 1.91kΩ 1% 1/4W brown-white-brown-brown-brown 141930
1 R40 4.12kΩ 1% 1/4W yellow-brown-red-brown-brown 144130
1R9 9kΩ 1% 1/4W white-black-black-brown-brown 149030
1 R38 10kΩ 1% 1/4W brown-black-black-red-brown 151030
1 R43 11kΩ 1% 1/4W brown-brown-black-red-brown 151130
2 R39, R42 39.2kΩ 1% 1/4W orange-white-red-red-brown 153930
1 R44 76.8kΩ 1% 1/4W violet-blue-gray-red-brown 157630
1 R10 90kΩ 1% 1/4W white-black-black-red-brown 159030
1 R45 158kΩ 1% 1/4W brown-green-gray-orange-brown 161530
2 R14, R15 240kΩ 5% 1/4W red-yellow-yellow-gold 162400

OR red-yellow-black-orange-green
1 R11 909kΩ 1% 1/4W white-black-white-orange-brown 169060
1 VR2 200Ω / 220Ω Potentiometer 191320

Note: Resistor tolerance (last band) of 5-band resistors may be green instead of brown.

CAPACITORS

Qty. Symbol Value Description Part #

4 C10 - C13 .01µF (103) Mylar 241017

SEMICONDUCTORS

Qty. Symbol Value Description Part #

1 U4 324 / 17324 Integrated Circuit 330324
4 D3 - D6 1N4001 or 1N4007 Diode 314001
1 D11 1N4148 Diode 314148

MISCELLANEOUS

Qty. Symbol Description Part #

2h

FE, CX 9-pin Socket 664009

1 U4 IC Socket 14-pin 664014

SECTION E

Capacitance and Transistor Testing Circuit

PTC - Thermister 1kΩ

Mount part in holes shown only

DO NOT PROCEED TO SECTION E WITHOUT INSTRUCTOR’S APPROVAL.