Global 1420 User Manual

1320

Model 1420

AC Power Supply

User Manual

1420 AC Power Supply

TEST INSTRUMENT SAFETY

WARNING

An electrical shock causing 10 milliamps of current to pass through the heart will stop most human heartbeats. Voltage as low as 35
volts dc or ac rms should be considered dangerous and hazardous since it can produce a lethal current under certain conditions. Higher
voltages are even more dangerous. Your normal work habits should include all accepted practices to prevent contact with exposed high
voltage, and that will steer current away from your heart in case of accidental contact with a high voltage. You will significantly
reduce the risk factor if you know and observe the following safety precautions:

1. The

2. Use only a polarized 3-wire ac outlet. This assures that the power supply chassis, case, and ground terminal are connected to a

3. When servicing any equipment equipped with a two-wire ac plug, treat it as “hot chassis” type and connect it to the ISOLATED

4. Never connect two pieces of “hot chassis” equipment to ISOLATED OUTPUT outlets simultaneously. There may be a serious

5. Don’t expose high voltage needlessly. Remove housings and covers only when necessary. Turn off equipment while making

6. If possible, familiarize yourself with the equipment being tested and the location of its high voltage points. However,

7. Use an insulated floor material or a large, insulated floor mat to stand on, and an insulated work surface on which to place

8. Use the time proven “one hand in the pocket” technique while handling an instrument probe. Be particularly careful to avoid

9. When testing ac powered equipment, remember that ac line voltage is usually present on some power input circuits such as the

10. Never work alone. Someone should be nearby to render aid if necessary. Training in CPR (cardio-pulmonary resuscitation)

Global Specialties Model 1420 AC Power Supply is a sou

instrument should be a qualified electronics technician or otherwise trained and qualified to work with high voltag

good earth ground and reduces danger from electrical shock.

OUTPUT outlet of the ac power supply. Even some equipment with a polarized plug are considered the “hot chassis” type.

shock hazard between two chassis.

test connections in high-voltage circuits. Discharge high-voltage capacitors after removing power.

remember that high voltage may appear at unexpected points in defective equipment.

equipment; and make certain such surfaces are not damp or wet.

contacting a nearby metal object that could provide a good ground return path.

on-off switch, fuses, power transformer, etc. any time the equipment is connected to an ac outlet, even if the equipment is
turned off.

first aid is highly recommended.

rce of high voltage ac. The person using the

e.

TABLE OF CONTENTS

page

TEST INSTRUMENT SAFETY ..................... inside front cover

FEATURES ................................................................................ 3

SPECIFICATIONS ..................................................................... 4

CONTROLS AND INDICATORS ............................................. 6

OPERATING INSTRUCTIONS .............................................. 12

Precautions ................................................................................ 12

Troubleshooting: Using the AC Power Supply as an

Isolation Transformer ........................................................ 16

Troubleshooting: Using the AC Power Supply as a

Variable AC Voltage Source. ....................................... ….21

Troubleshooting: Using the AC Power Supply to

Measure Electrical Loads .................................................. 23

Using the Model 1420 as a Leakage Tester .............................. 25

Soldering Iron Temperature Control ......................................... 27

page

CIRCUIT DESCRIPTION..........................................................29

MAINTENANCE AND CALIBRATION..................................30

Preventive Maintenance...............................................................30

Returning for Service...................................................................30

Fuse Replacement........................................................................30

Auto-Transformer Brush Replacement........................................31

Calibration Adjustments..............................................................31

Performance Tests........................................................................34

Troubleshooting...........................................................................35

CUSTOMER SUPPORT.............................................................37

WARRANTY INFORMATION.................................................37

Warranty Service Instructions......................................................38

2

WIDE VOLTAGE RANGE

Output voltage continuously variable from 0 to 150VAC.

WIDE CURRENT RANGE

Model 1420

Heavy duty unit handles virtually all servicing needs.
Output current up to 3 amps continuous, 4 amps
intermittent.

WIDE LOAD MEASUREMENT CAPABILITY

Model 1420

Built in multi-function meter. 0-150V. Two current
ranges of 0-2A and 0-4A for improved resolution. Current
scales also calibrated in VA at 120V.

ISOLATED OUTPUT VOLTAGE

Built-in isolation transformer for safe servicing of “hot
chassis” equipment. Two
isolated outlets on Model 1420.

FEATURES

Built-in solid state soldering iron temperature control.

BUILT-IN METER

Model 1420

3-1/4 inch meter. Multi-color scales. Overrange

protection.

---Model 1420 offers the following additional features---

POWER LINE LEAKAGE TEST

OSHA, UL, and CSA power line leakage test capability; fast
and safe measurement.

EXPANDED LEAKAGE SCALE

0-5mA (0-5000µA) leakage scale is expanded in most
commonly used 100-500µA portion, compressed to 5 mA

full scale. Overload protected.

CIRCUIT BREAKER OVERLOAD PROTECTION

Isolated output protected by easily reset circuit breaker.

SOLDERING IRON TEMPERATURE CONTROL

Built-in solid state soldering iron temperature control

3

4

SPECIFICATIONS

MODEL 1420

OUTPUT ISOLATION

Leakage less than 0.1mA (25ºC, 50% relative humidity.)

VOLTAGE ADJUSTMENT RANGE

0-150VAC, with input at 120VAC

VOLTAGE/CURRENT SENSING

Sine wave average, calibrated in RMS

MAXIMUM CURRENT (Isolated)

3A continuous, 4A intermittent (0-130V). Intermittent not to

exceed 4 minutes at 4A followed by 5 minutes at 1A max.

METER SCALES

Voltage ..................................................................... :0-150V

Current:. ........................................................................ 0-2A

......................................................................... 0-4A

Volt-Amps (Voltage Set to 120) ............................ 0-240VA

................................................................. 0-480VA

Leakage ...................... 0 to 5mA (5,000µA), expanded scale

METER ACCURACY (25ºC)

Volts:......................±5% of full scale (calibrated @ 120VAC)

Current:...........................................................±5% of full scale

Leakage:............................................................±5% @ 500µA

FRONT PANEL CONTROLS

(Refer to Fig. 1)

1. POWER ON Switch.

2. POWER ON Pilot Light.

3. Function Switch.

Model 1420

Five interlocking pushbutton switches which select
function and meter scale. Pressing a button releases
the previous selection. The following selections are
available:

VOLTS. Connects meter to measure voltage at

ISOLATED OUTPUT. Use 0-150 VOLTS
scales on meter. Voltage is adjustable with AC
VOLTS control.

AMPS 0 – 4. Connects meter to measure current of

ISOLATED OUTPUT. USE 0-4 AMPS scale on
meter. When voltage is set to 120 VAC, the 0-480
VA scale may be used to measure the output load
in volt-amps

AMPS 0-2. Connects meter to measure current of

ISOLATED OUTPUT. Use 0-2 AMPS scale on
meter. When voltage is set to 120VAC, the
0-240VA scale may be used to measure the
output load in volt-amps.

LEAKAGE COM. Connects meter to measure leakage with

respect to common side of ac line. Use LEAKAGE scale on
meter. Voltage must be preset to 120VAC for accurate
leakage measurements.

LEAKAGE HOT. Connects meter to measure leakage with

respect to hot side of ac line. Use LEAKAGE scale on
meter. Voltage must be preset to 120VAC for accurate
leakage measurements.

4. Meter. Appropriate scale is selected by function switch.

5. AC VOLTS Control. Adjusts voltage at ISOLATED

OUTPUT receptacle(s) from 0 to 150 volts.

6

8

Figure 1. Front Panel Controls and Indicators, Model 1420

10

Figure 3. Rear Panel Controls and Indicators, Model 1420

OPERATING INSTRUCTIONS

PRECAUTIONS

SAFETY

The Model 1420 AC Power Supply is a source of
high voltage ac. Improper or careless use could result in fatal
electrical shock. The most commonly encountered conditions
which may pose a shock hazard are identified and corresponding
precautions listed in the TEST INSTRUMENT SAFETY section
which starts on the side front cover of this manual. Know and
observe these precautions.

Although Model 1420 is equipped with dual isolated outlets,
only one “hot Chassis” equipment should be connected at a time.
Unless the line-to-chassis relationship is identical, a shock hazard
will exist between the two chassis.

INPUT POWER

These instruments are intended for use only with 120 volt,
60Hz line voltage. Do not operate from 50Hz, or 220-240 volt
power systems. The instrument may be safely operated from 100
volt, 60Hz line voltage, although the maximum output voltage
will be lower.

VENTILATION

The holes in the case provide convection cooling (hot air rises
and escapes through the top vents, while cool air is drawn in to
replace it through the bottom). Never block these ventilation
holes with a manual, schematic diagram, other equipment, etc. If
the air is blocked, the temperature inside the ac power supply may

become excessive and cause failure of the unit. Similarly, avoid
operating locations near sources of heat.

MAXIMUM OUTPUT VOLTAGE

Exceeding the maximum input voltage rating of the equipment

under test (typically 130VAC) may cause severe damage to the

The output voltage of the ac power supply is adjustable from 0
to 150VAC. This is very useful in certain testing situations for
stressing equipment beyond its normal operating range to
determine its breakdown point. However, for most testing and
servicing applications, input voltages higher than the maximum
specified by the manufacturer should be used with great
precaution.

For normal testing and servicing, check the maximum input
voltage specification of the equipment under test and make sure
you do not adjust the output voltage of the ac power supply
higher than that value. Most ac powered equipment has a
maximum input voltage rating of 130VAC. If unsure of the
maximum rating, do not exceed 130 VOLTS. On Model 1420,
the 130-150 volt portion of the VOLTS scale is red as a reminder
that caution should be observed.

CAUTION

equipment.

12