Elenco Electronics XP-650, XP-750 Instruction Manual
VARIABLE REGULATED
POWER SUPPLY
MODELS XP-650 / XP-750
Instruction Manual
Elenco Electronics, Inc.
Copyright © 1989 Elenco Electronics, Inc. Revised 1998 REV-D 753650
Model XP-750
Model XP-650
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Table of Contents
Safety Precautions Page 2
Specifications Page 2
Operating Instructions Page 3
Introduction Page 3
Circuit Description Page 3
Power Source Page 4
0-20V or 0-40V Regulators Page 4
XP-750 Digital Meters Page 5
Maintenance and Calibration Page 6
Variable 0-20VDC Regulator Calibration Page 6
Variable 0-40VDC Regulator Calibration Page 6
Digital Meter Calibration on Model XP-750 Page 6
Parts List XP-650 Page 7
Parts List XP-750 Page 8
Schematic Diagram XP-650 Page 9
Schematic Diagram XP-750 Page 10
Specifications for Model XP-650
Input Voltage 120VAC or 240VAC (factory set)
Output Voltage 0-20VDC or 0-40VDC
Output Current 3 Amps @ 0-20VDC
1.5 Amps @ 0-40VDC
Load Regulation Less than .1V (0 to full load)
Line Regulation Less than .1V (105 to 135V)
Ripple and Noise Less than .005V RMS
Current Protection .05 to 3A adjustable current limit
Short Protection .05 to 3A limit automatic reset
Output Impedance .025 ohms
Meter 40 Volts and 3 Amps, 5% full scale accuracy
Specifications for Model XP-750
Input Voltage 120VAC or 240VAC (factory set)
Output Voltage 0-20VDC to 0-40VDC
Output Current 3 Amps @ 0-20VDC
1.5 Amps @ 0-40VDC
Load Regulation Less than .1V (0 to full load)
Line Regulation Less than .1V (105 to 135V)
Ripple and Noise Less than .005V RMS
Current Protection .05 to 3A adjustable current limit
Short Protection .05 to 3A limit automatic reset
Output Impedance .025 ohms
Meters Two LED type meters. The voltmeter accuracy is better than 1/2% +
1 digit.
Resolution is 100mV. The ammeter accuracy is better than 1% +
1 digit.
Resolution is 10mA.
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Safety Precautions
CAUTION: When removing cover or replacing fuse, always disconnect the power cord from the AC
socket. Service repair should be done by qualified personnel who are knowledgeable of electrical hazards.
Certain safety precautions 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. Y ou should thoroughly familiarize yourself with the equipment before working on it. High voltage may appear at unexpected points in defective equipment.
Elenco power supplies are equipped with three wire line cords which ground the chassis to the power
line cord. DO NOT CUT OFF OR DISABLE THE GROUND PLUG.
The power supply secondary circuits are isolated from the 120V primary circuit via the power transformer. When working with the 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.
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Operating Instructions
1.
Check the voltage rating of the equipment to be powered. Care must be taken not to exceed this rating.
2. Plug the line cord into a 120V 60Hz AC outlet.
3. Set the voltage switch to 0-20V if the voltage required is under 20V. This assures cool operation of the
heat sinks. Adjust the voltage control to the desired voltage. 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 terminal and the negative lead to the black
terminal. The power should be turned off during this operation.
5. Adjust the current limiting control to maximum counter-clockwise position. Switch your equipment on.
The overload light will glow if more than 50 milliamps 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. An
alternate method of adjusting current limiting is to short the output and adjust the current to a desired
value. Remove the short. This will now limit the current to your setting.
Introduction
The Model XP-650 and XP-750 are solid-state DC power supplies, continuously variable from 0 to 40 volts.
Two current ranges are available, 0-20V @ 3 amps and 0-40V @ 1.5 amps. The units are precisely held to
the desired output voltage by a special regulating circuit. Maximum output current is externally adjustable
from .05 to 3 amps. An overload indicating lamps glows when current approaches limiting conditions. This
circuit is designed to protect the power supply against shorts or excessive demand. It also protects the
equipment from possible damage due to high surge currents. This supply is ideal for use in school labs,
service shops or anywhere a precise DC voltage is required.
Circuit Description
The Elenco Models XP-650 and XP-750 use the same power and regulator circuits. The only difference is
in the display functions. The Model XP-650 uses a 0-40V and a 0-3A analog meter. Model XP-750 has two
digital meters to read voltage and current. The voltmeter has better than 1/2% accuracy . The current meter
has better than 1% accuracy.
Both models basically have two independent regulated power supplies. These supplies, when placed in
series, will give 0-40 volts @ 1.5 amps. When they are placed in parallel, the output voltage will be 0-20
volts @ 3 amps.
The basic circuits of these supplies consist of 1) The power source, 2) The regulator and 3) The readout circuits. 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
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