Elenco Electronics XP-660, XP-760 Instruction Manual

POWER SUPPLY

MODELS XP-660 / XP-760

Variable Regulated

Model XP-660

Model XP-760

Instruction Manual

Elenco®Electronics, Inc.

ight © 2005, 1990 b

yr

Cop

t of this book shall be reproduced b

No par

y Elenco

®

Electronics

y means; electronic, photocopying, or otherwise without written permission from the publisher.

y an

, Inc.

ights reser

All r

ved. Revised 2005 REV-H 753660

Specifications for Model XP-660 @ 120VAC input

0-20V Supplies 5V Supply

Input Voltage 110-135VAC 60 Hertz Same
Output Voltage 0-20VDC Variable 5VDC + .1V
Output Current 0-1A over 0-20V range 0-5A
Load Regulation Less than .1V over 0-20V range Less than .15V
Line Regulation Less than .1V 110V to 130V Less than .15V
Ripple RMS Less than 5mV Less than 10mV
Current Protection .05 to 1A Variable current limiting Current foldback
Short Protection .05 to 1A current limit Current foldback
Output Impedance .1 ohms .03 ohms

Specifications for Model XP-760 @ 120VAC input

0-20V Supplies 5V Supply

Input Voltage 110-135VAC 60 Hertz Same
Output Voltage 0-20VDC Variable 5VDC + .1V
Output Current 0-1A over 0-20V range 0-5A
Load Regulation Less than .1V over 0-20V range Less than .15V
Line Regulation Less than .1V 110V to 130V Less than .15V
Ripple RMS Less than 5mV Less than 10mV
Current Protection .05 to 1A Variable current limiting Current foldback
Short Protection .05 to 1A current limit Current foldback
Output Impedance .1 ohms .03 ohms

-1-

Circuit Description

The Elenco®XP-660 and XP-760 use the same
basic power and regulator circuit. The only
difference is in the display function. The XP-660 has
two 0-1mA analog meters. These meters convert to
a voltmeter by placing a 20kΩ resistor in series or
an ampmeter by placing a .39Ω shunt resistor
across the meter.

The Model XP-760 has two 3 1/2 digit LED meters.
Voltage is read by connecting the meter to a voltage
divider on the power supply output. Current is read
by connecting the meter to a shunt resistor in series
with the power supply output.

When referring to the schematic diagrams, the
circuit components associated with each supply can
be identified by its number. The 5V supply begins
with 100. The 0-20V Power One Supply begins with
300 numbers and the 0-20V Power Two Supply
begins with 200 numbers. The basic circuit of these
supplies consist of 1) The power source, 2) The
regulator and 3) The readout circuit. These circuits
are shown in Figure 1 and will be discussed in detail
in the following paragraphs.

Figure 1 Block Diagram of 0-20V Power Supply

Power Source

The power supply f
consists of a tr
down windings. Connected to each winding is a
diode bridge and a filter capacitor
on the Power One Supply are diodes D301, D302,
D303, D304 and capacitor C304. These
components con

or Models XP-660 and XP-760

ansformer with f

vert the 120VAC input to 25VDC.

our isolated step

. The components

0-20V Regulators

Figure 2 shows a simplified circuit of the 0-20V
regulator circuit. This circuit consists of a high gain
amplifier transistor Q305. The gain of this stage is

ver 100,000 because of its extremely high load

o

This load consists of a current source

impedance
transistor Q301 and its biasing circuit. The effective
resistance of this circuit is over 500,000 ohms.
Transistor Q302 is a power device that controls the
output current. Transistors Q303 and 304 are
emitter f
current source
a closed negative feedback loop. If you analyze this
loop you will find that when the output voltage goes
down due to increase output current, the voltage at
the base of transistor Q305 goes negative. This
reduces the current in tr

.

ollowers used to prevent loading of the

Q301, Q302, Q305 and

.

ansistor Q305 and thus the

VR303 f

orm

collector voltage will increase, returning the output
voltage to very near its original value. The high gain
is essential to the output voltage. Diode D309 is
added to prevent drift with temperature changes
and to allow the output voltage to go to zero.

To protect the regulator from overloads and short
circuits
voltage drops across resistor R309 reaches .6V,
tr
v
limiting, transistor Q306 is prebiased via resistor
R309 and VR301 (see XP-660 schematic). This will
allow the output current limit between .05 and 1
amp. Transistors Q307 and Q308 are added to light
the o

, transistor Q306 is added. Whenever the

ansistor Q306 will conduct and lower the collector

oltage of amplifier Q305. To obtain variable current

load LED

er

v

.

-2-

5V Regulator

The circuit of the 5V regulator is shown on the
schematic with components beginning with number

100. The heart of the regulator is IC1. This IC
contains the same basic circuit as the 0-20V
regulator, previously described (see schematic
diagram of XP-660). Transistor Q102 is the pass
transisitor that controls the output current. Transistor
Q101 is used to increase the impedance of the pass
transistor. Resistor R104 senses the current and
shuts down the IC if the current exceeds 5 amps.
The regulator features a current foldback circuit
which reduces the current to less than 1 amp when
the output is shorted. Resistors R105 and R106 form
the current foldback circuit. Resistors R102 and
R103 are added to form a stable 3.9V reference
voltage for the IC to operate.

Timing for the overall operation of the A/D converter
is derived from a 40kHz external oscillator. The IC
divides this frequency by four and the resulting clock
pulses are used to drive its decade counters. It is
then further divided to form three convert-cycle
phases. The final readout is clocked at about 2.5
readings per second.

The digitized data is presented to the display as four
decoded digits (seven segments) plus polarity. The
decimal point position on the display is selected by
the Volts/Amps switch.

A/D Converter - Any given measurement cycle
performed by the A/D converter can be divided into
three consecutive time periods, autozero (AZ),
integrate (INTEG) and read. A counter determines
the length of the time periods. The integrate period
is fixed at 1,000 clock pulses. The read period is a
variable time that is proportional to the unknown
input voltage. It can vary from zero counts for zero
input v
voltage. The autozero period varies from 1,000 to
3,000 counts. For an input voltage less than full
scale autozero gets the un
period.

oltage to 2,000 counts for a full scale input

used por

tion of the read

Figure 2 Simplified Regulator Circuit

XP-760 Digital Meters

Meter operation centers around the 7107 integrated
circuit (IC). This chip contains a dual slope A/D

ter, display latches, seven

er

(analog to digital) con
segment decoder

The input of the 7107 IC is fed to an A/D converter.
Here the DC voltage is changed to a digital format.
The resulting signals are processed in the decoders
to light the appropr

v

, and display drivers.

iate LED segments

.

ing the autozero cycle the accumulated offset

Dur
voltage errors in the converter are measured and
stored as a voltage on the external autozero
capacitor
offset voltage errors during the read cycle.

Dur
charged up for 1,000 clock pulses (100ms.), see
Figure 3. The charging rate is determined by the
unknown input voltage. At the end of the integrate
cycle the voltage on the capacitor is proportional to
the unknown input voltage.

Dur
discharged at a constant r
the discharge is therefore proportional to the
unknown input voltage. This time is converted to a
digital format by counting the number of clock
pulses that occur dur

. This v

ing the INTEG cycle the INTEG capacitor is

ing the read cycle the INTEG capacitor is

oltage is used to correct for the

ate. The time required for

ing the discharge.

-3-

Counter Output

Figure 3 Dual Slope A/D Converter

Operation Instructions

1)

Check the v
powered. Care must be taken not to exceed this
rating.

2) Plug the line cord into a 120V 60Hz AC outlet.

Adjust the v

3)
Load variation will have practically no effect on
the voltage setting due to the special regulation
circuit.

4) Connect the positive lead of your equipment to
the red output ter
negative lead to the black terminal marked (–).

5) Adjust the current limiting control to maximum
counter-clockwise position. Switch your
equipment on. The overload light will glow if
excessive current is drawn. Increase this control
until the light goes out and stays out during
normal use. Your equipment is now protected
from high current surges
of adjusting current limiting is to shor
and adjust the current to a desired v
Remove the short. This will now limit the current
to your setting.

Meters can be switched to read voltage or

6)
current.

oltage rating of the equipment to be

oltage control to the desired voltage

minal marked (+) and the

. An alternate method

t the output

alue.

Elenco

®

Models XP-660 and XP-760 are e

xtremely
versatile power supplies. All supplies are
completely isolated from each other. This means
that they ha

ve separate g

rounds. By tying the
ground terminal of one supply to the positive
terminal of the other, you can obtain an output of 0-

.

40V @ 1 ampere

. Also by stac

king the 5V ter

minal

you can increase the output to 45V.

The 0-20V supplies have an adjustable current
overload feature, a red LED will light when current
limiting is activated. The current limit control adjusts
the maxim

um current the supply will allow bef

ore
automatically turning down the output voltage. This
limit is between 50mA to 1 amp. You can set it to
your desired limit by shorting out the output terminal
and adjusting the current limit control to the desired
current. Remove the short and attach the load. The
maximum current drawn will be per your setting.

All three power supplies are protected against

xternal shorts. The 0-20V supplies are protected

e

If the output is

y the current limiting f

b

ted the maximum current drawn will depend on

shor

eature

.

the limit control setting. The 5V supply features a
current foldback circuit. This circuit will limit the
output current to less than 1 amp. When the short
is remo
reset to 5V

ved, the output voltage will automatically

.

-4-

Safety Precautions

Certain safety procedures must be observed when
this power supply is used with external circuits that
are connected to AC power lines. There is always
some danger when working with electrical
equipment or circuits that operate at hazardous
voltages. You should thoroughly familiarize yourself
with the equipment before working on it. High
voltage may appear at unexpected points in
defective equipment.

The Elenco
wire line cords which ground the chassis to power
line cord. DO NOT CUT OFF OR DISABLE THE

GROUND PLUG.

®

power supplies are equipped with three

Variable 0-20VDC Regulator
Calibration

1) Connect an accurate digital meter to the output

of the 0-20V supply.

2) Set the voltage pot to maximum position.

3) Adjust the variable resistor VR302 of Power One

Supply for 20.0V. Adjust VR203 for Power Two
Supply.

Digital Meter Calibration
for Model XP-760

1) Note the small pot (R2) on the top of each

meter’s PC board. This is the GAIN pot which
controls the accuracy of the meter.

The power supply secondary circuits are isolated
from the 120V primary circuit via the power
transformer. When working with other equipment, this
may not always be the case. Always be familiar with
the equipment rating. Keep in mind that defective
equipment can have dangerous voltages at
unexpected points. CAUTION: When removing the
cover for fuse replacement, always disconnect the
power cord from the AC socket. Service repair should
only be done by qualified personnel who are
knowledgeab

le of electrical hazards.

Maintenance and Calibration

The Elenco®Models XP-660 and XP-760 have been
designed and manufactured to require no routine
maintenance. The circuits are protected by design
from e
information is provided in the event the supply requires
service or re-calibration.

xternal shor

ts or over

loads. The following

Fixed 5VDC Regulation Calibration

1) Connect an accurate digital meter to the output
of the 5V supply.

2) Adjust the variable resistor VR101 to read

5.0VDC.

2) To set the accuracy of the meter you need
another very accurate digital meter. Connect
this meter to measure the voltage on the output
terminals of the supply under adjustment. Set
the output to 18VDC
to Volts and adjust the GAIN pot for 18.0 on the
XP-760 meter.

3) To set the accuracy of the current measurement
connect a suitable load to the output and
connect the accur
the current in the load. Set the Volts/Amps
switch to Amps. Set the output current to 0.8

. Adjust VR304 (P

amps
VR204 (Power Two Supply) for a reading of 0.8
on the XP-760 meter.

. Set the Volts/Amps switch

ate digital meter to measure

ower One Supply) or

-5-

Parts List XP-660

Qty. Description Part #

Qty. Description Part #

Resistors

2 R105 .14Ω 5% 5W 101405
2 R213, 313 .39Ω 5% 2W 103911
2 R210, 310 68Ω 5% 1/4W 126800

R208, 209, 308, 309 200Ω 5% 1/4W 132000

4
2 R211, 311 270Ω 5% 1/4W 132700
4 R202, 203, 302, 303 470Ω 5% 1/4W 134700
3 R101, 222, 322 1kΩ 5% 1/4W 141000
4 R206, 214, 306, 314 1.2kΩ 5% 1/4W 141200
2 R201, 301 1.2kΩ 5% 1/2W 141201
2 R205, 305 2kΩ 5% 1/4W 142000
2 R215, 315 3.3kΩ 5% 1/4W 143300
1 R102 10kΩ 5% 1/4W 151000
2 R217, R317 20kΩ 1% 1/4W 152030
3 R103, 204, 304 22kΩ 5% 1/4W 152200
1 R104 27kΩ 5% 1/4W 152700
2 R216, 316 100kΩ 5% 1/4W 161000
2 R218, 318 200Ω Trim Pot LD 191320
3 VR101, 202, 302 5k
2 VR201, 301 200
2 R203, 303 5k

Ω Trim Pot SU 191451

Ω Pot Panel 192320

Ω Pot Panel 192450

Capacitors

3 C104, 206, 306 .001
5 C103,201,202,301,302 100
2 C205, 305 100µF Lytic 35V 281046
3 C105, 210, 310 100µF Lytic 25V 281055

2 C203, 303 2200µF Lytic 25V 292225
2 C204, 304 3300µF Lytic 50V 293347
2 C101, 102 4700µF Lytic 16V 294744

µF Disc 231036

µF Lytic 25V 281045

(axial)

Semiconductors

1 BR1 Diode bridge 6A 310148
2 D211, 311 Diode 1N4001 314001
15 D101, 201-206, 209, Diode 1N4002 314002

D301-306, 309
4 D207, 208, 307, 308 Diode 1N4148 314148
2 D210, 310
4 Q201, 207, 301, 307
1 Q101 Transistor TIP120 320120
3 Q102, 202, 302 Transistor 2N3055 323055
8 Q204-206, 208,

Q304-306, 308

Q203, 303

2

IC IC MC1723 331723

1

LED201, 301 LED Red 350001

2

Diode Zener 1N5240 10V
Transistor MPSA70

Transistor MPS5172

Transistor MPS6521

315240
320070

325172

326521

Miscellaneous

1 Transformer 440660
1 PC Board 512010
1 Fuse 1.5A Slow Blow 520150
2 Switch slide DPDT 541111
1 Switch Illuminated 541204
2 Volt/Amp Meter 571020
1 Cover 611060
1 Chassis 611660
1 Heatsink 1 TO-3 615001
2 Heatsink Ham Rod 615100F
4 Knob 622009
1 Bushing Strain 3 wire 624003
3 Binding Post Black 625031

Binding Post Hex Nut 625031HN

7
7

Binding Post Lockwasher 625031LW
3 Binding Post Red 625032
1 Binding Post Green 625033
4 PCB Support 625001
2 LED Lens 626014
6 Cable Ties 628982
1 Rivet .122 632211
4 Screw M3 x 0.5 x 5mm phillips, black 640300
1 Screw 6-32 x 1/2” 641665
4 Screw 8-32 x 3/8” 641840
4 Screw 6 x 3/8” Truss, AB 642652
8 Screw 6 x 3/8” AB 642660
1 Nut 6-32 Small 644601
4 Nut 8-32 644800
4 Nut 7mm 644101
3 Washer Flat #8 645008
4 Washer 8mm 645101
6 Washer 1/8” 645600
11 Lockwasher 5/16” 646101
1 Loc
5 Lockwasher #8 Ext. 646828
2 Lug ground 661001
4 Lug Solder #8 661002
1 Fuse Holder Lower Body 663005LB
1 Fuse Holder Nut 663005N
1
1 Fuse Holder Washer 663005W
1 IC Socket 14-Pin 664014

kwasher #6 646600

Fuse Holder Upper Body 663005UB

-6-

Schematic Diagram XP-660

-7-

Schematic Diagram XP-760

-8-

Parts List XP-760

Qty. Description Part #

Qty. Description Part #

Resistors

2 R105 .14Ω 5% 5W 101405
2 R213, 313 .39Ω 5% 2W 103911
2 R210, 310 68Ω 5% 1/4W 126800

R207, 307 100Ω 5% 7W 131017

2
4 R208, 209, 308, 309 200Ω 5% 1/4W 132000
2 R211, 311 270Ω 5% 1/4W 132700
4 R202, 203, 302, 303 470Ω 5% 1/4W 134700
2 R219, 319 910Ω 5% 1/4W 139100
3 R101, 222, 322 1kΩ 5% 1/4W 141000
4 R206, 214, 306, 314 1.2kΩ 5% 1/4W 141200
2 R201, 301 1.2kΩ 5% 1/2W 141201
2 R307, 312 1.5kΩ 5% 2W 141503
2 R205, 305 2kΩ 5% 1/4W 142000
2 R215, 315 3.3kΩ 5% 1/4W 143300
1 R102 10kΩ 5% 1/4W 151000
3 R103, 204, 304 22kΩ 5% 1/4W 152200
1 R104 27kΩ 5% 1/4W 152700
2 R216, 316 100k
2 R217, 317 1M
2 VR201, 301 200
1 VR101 5kΩ Pot SU 191451
2 VR302, 303 10kΩ Pot SU 191516
2 VR204, 304 200Ω Pot Panel 192320
2 VR202, 203 10kΩ Pot Panel 192511
2 R220, 320

Ω 5% 1/4W 161000

Ω 5% 1/4W 171000

Ω Pot LD 191320

.01Ω Shunt Wire

897120

Capacitors

3 C104, 206, 306 Disc .001µF Z5V 231036
2 C209, 309 Disc .1µF 251010
2 C207, 307
7 C103, 201, 202, 205 Lytic 100µF 25V 281045

C301, 302, 305

3 C105, 210, 310
2 C208, 308 Lytic 220µF 25V 282245
2 C203, 303
2 C204, 304
2 C101, 102

Lytic 4.7µF 50V Radial

Lytic 100µF 25V Axial

Lytic 2200µF 25V
Lytic 3300µF 50V
Lytic 4700µF 16V

264747

281055

292225
293347
294744

Semiconductors

1 BR1
17 D201-206, 209, 211 Diode 1N4001 314001

D301-306, 309, 311
4 D207, 208, 307, 308 Diode 1N4148 314148
2 D210, 310
4 D201, 207, 301, 307
4 Q102, 202, 302

Q204, 206, 208,

8

Q304-306, 308

Q101 Trans. 6121/1061 326121

1

Q203, 303 Trans. MPS6521 326521

2

Diode bridge 6A

Diode Zener 1N5240 10V
Transistor MPSA70
Transistor 2N3055
Transistor MPS5172

310148

315240
320070
323055
325172

Semiconductors (Con’t)

1 IC101 MC1723 331723
2 IC201, 301 MC7805CT 337805
2 LED201, 301 LED Red 350001

Miscellaneous

2 LED Display 355614MI
1 Transformer 440660
1 PC Board 512010
1 Fuse 1.5A Slow Blow 520150
2 Switch 3PDT 541047
1 Switch Illuminated 541204
1 Cover 611060
1 Chassis 611760
1 Heat Sink 5V 615001S
2 Heat Sink Clip On 615005
2 Heat Sink 20V 615100F
4 Knob Push On 622009
1 Bushing 624003
4 PCB Support 625002
3 Binding Post Black 625031
7 Binding Post Lockwasher 625031LW
7 Binding Post Hex Nut 625031HN
3 Binding Post Red 625032
1 Binding Post Green 625033
2 LED Lens Red 626014
5 Cable Tie 628982
7 Rivet .122 632211
2 Screw 6-32 x 1/2” 641665
4 Screw 8-32 x 3/8” 641840
4 Screw 6 x 3/8” Truss, AB 642652
8 Screw 6 x 3/8” 642660
4 Nut Hex 7mm 644101
1 Nut 6-32 644600
1 Nut 6-32 Small 644601
4 Nut 8-32 644800
3 Washer Flat #8 645008
4 Flat Washer Pot 8 x 14mm 645101
4 Washer Fiber #4 645404

Flat Washer 1/4” OD 645600

7

kwasher #6 646600

Loc

1

kwasher #8 Ext. 646828

Loc

5

Lockwasher Pot 3/8” 646900

4

Lug Ground 661001

2

Butt Connector 661100

1

Feet 662001

4
1 Fuse Holder Lower Body 663005LB
1 Fuse Holder Nut 663005N
1 Fuse Holder Upper Body 663005UB
1 Fuse Holder Washer 663005W
1 Line Cord 3 Wire 862105

-9-

WARRANTY POLICY

All of our instruments have been tested and conform to our rigid requirements on
performance and durability, they are guaranteed to be free of defects in
workmanship, materials and construction for a period of 2 years. If this product
should f
will repair or replace the unit at no cost. For the remainder of the warranty period, a
nominal service charge is required to cover shipping and handling. Elenco®will either
repair or, at its sole option, replace any par
and other optional materials which are defective in either workmanship or material
under nor

This warranty does not cover equipment which has been tampered with in any way,
or damage caused b
unassembled products
properly packed and insured, and must include proof of purchase. This warranty
applies only to the or

EXPRESSED OR IMPLIED
DAMAGES. Please contact Elenco®for further instructions before returning your

instr

ail in normal use within the first 3 months from the date of purchase, Elenco

xcept for fuses

t e

, probes, lamps, batteries

mal and proper use.

y accident, negligence

. This product must be retur

iginal purchaser.

. ELENCO

®

IS NO

, alteration, misapplication or

ansportation prepaid,

NO O

ned tr

THER WARRANTIES ARE

T LIABLE FOR CONSEQUENTIAL

ument.

®

Direct all warranty inquiries to:

Elenco

150 Carpenter Avenue,Wheeling, IL 60090 • Phone: [phone]

®

Electronics, Inc. • Service Department

-10-

Elenco®Electronics, Inc.

150 Carpenter Avenue

Wheeling, IL 60090

[phone]

Fax: [phone]

Web site: www.elenco.com

e-mail: [e-mail]