B&K Precision 1655A User Manual [en, es]
INSTRUCTION
MANUAL
MANUAL DE
INSTRUCCIÓN
MODELS 1653A & 1655A
MODELOS 1653A & 1655A
Isolated-Variable
AC POWER SUPPLY
Aislada, variable
FUENTE DE PODER DE AC
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 B+K Precision Models 1655A and 1653A AC Power Supplies are sources of high voltage ac. The person using the
instrument should be a qualified electronics technician or otherwise trained and qualified to work with high voltage.
2. Use only a polarized 3-wire ac outlet. This assures that the power supply chassis, case, and ground terminal are connected to a
good earth ground and reduces danger from electrical shock.
3. When servicing any equipment equipped with a two-wire ac plug, treat it as “hot chassis” type and connect it to the ISOLATED
OUTPUT outlet of the ac power supply. Even some equipment with a polarized plug is the “hot chassis” type.
4. Never connect two pieces of “hot chassis” equipment to ISOLATED OUTPUT outlets simultaneously. There may be a serious
shock hazard between two chassis.
5. Don’t expose high voltage needlessly. Remove housings and covers only when necessary. Turn off equipment while making
test connections in high-voltage circuits. Discharge high-voltage capacitors after removing power.
6. If possible, familiarize yourself with the equipment being tested and the location of its high voltage points. However,
remember that high voltage may appear at unexpected points in defective equipment.
7. Use an insulated floor material or a large, insulated floor mat to stand on, and an insulated work surface on which to place
equipment; and make certain such surfaces are not damp or wet.
8. Use the time proven “one hand in the pocket” technique while handling an instrument probe. Be particularly careful to avoid
contacting a nearby metal object that could provide a good ground return path.
9. When testing ac powered equipment, remember that ac line voltage is usually present on some power input circuits such as the
on-off switch, fuses, power transformer, etc. any time the equipment is connected to an ac outlet, even if the equipment is
turned off.
10. Never work alone. Someone should be nearby to render aid if necessary. Training in CPR (cardio-pulmonary resuscitation)
first aid is highly recommended.
Instruction Manual
for
MODELS 1653A & 1655A
Isolated, Variable
AC POWER SUPPLY
22820 Savi Ranch Parkway
Yorba Linda, CA 92887
www.bkprecision.com
TABLE OF CONTENTS
page
TEST INSTRUMENT SAFETY..................... inside front cover
FEATURES................................................................................ 3
SPECIFICATIONS ....................................................................4
CONTROLS AND INDICATORS ............................................6
OPERATING INSTRUCTIONS.............................................. 12
Precautions ...............................................................................13
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 1655A 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.................................................38
Warranty Service Instructions......................................................38
Spanish Manual............................................................................39
2
WIDE VOLTAGE RANGE
Output voltage continuously variable from 0 to 150VAC.
WIDE CURRENT RANGE
Model 1655A
Heavy duty unit handles virtually all servicing needs.
Output current up to 3 amps continuous, 4 amps
intermittent.
Model 1653A
Handles many servicing needs. Output current up to 2
amps continuous.
WIDE LOAD MEASUREMENT CAPABILITY
Model 1655A
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.
Model 1653A
Built in dual-purpose meter measures output voltage from 0150V and output current from 0-2A.
ISOLATED OUTPUT VOLTAGE
Built-in isolation transformer for safe servicing of “hot
chassis” equipment. One isolated outlet on Mode 1653A, two
isolated outlets on Model 1655A for greater convenience.
Unless otherwise stated, all information in this section applies equally to Model 1653A and 4655A
FEATURES
BUILT-IN METER
protection
-
POWER LINE LEAKAGE TEST
EXPANDED LEAKAGE SCALE
full scale. Overload protected.
Built-in solid state soldering iron temperature control.
CIRCUIT BREAKER OVERLOAD PROTECTION
SOLDERING IRON TEMPERATURE CONTROL
3
Model 1655A
3-1/4 inch meter. Multi-color scales. Overrange
Model 1653A
2 inch meter. Overrange protection.
---Model 1655A offers the following additional features--
OSHA, UL, and CSA power line leakage test capability; fast
and safe measurement.
0-5mA (0-5000µA) leakage scale is expanded in most
commonly used 100-500µA portion, compressed to 5 mA
Isolated output protected by easily reset circuit breaker.
Built-in solid state soldering iron temperature control
SPECIFICATIONS
OUTPUT ISOLATION
Leakage less than 0.1mA (25ºC, 50% relativ
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% (typical) of full scale (calibrated @ 120VAC)
Current:.............................................±5% (typical) of full scale
Leakage:............................................................±5% @ 500µA
MODEL 1655A
e humidity.)
OUTPUT ISOLATION
Leakage less than 0.1mA (25ºC, 50% relativ
VOLTAGE ADJUSTMENT RANGE
0-150VAC, with input at 120VAC
VOLTAGE/CURRENT SENSING
Sine wave average, calibrated in RMS.
MAXIMUM CURRENT (Isolated)
2A continuous (0-130V).
METER SCALES
Voltage:.........................................................................0-150V
Current:.............................................................................0-2A
METER ACCURACY (25ºC)
Volts:........±5% (typical) of full scale (calibrated @ 120VAC)
Current:............................................±5% (typical) of full scale
MODEL 1653A
e humidity)
4
MODEL 1655A
AC INPUT
120 VAC, 60Hz, 600 VA*
OPERATING TEMPERATURE RANGE
0° C to +40°C.
STORAGE TEMPERATURE
-30° C to +60°C.
WEIGHT
22lb (10kg.)
DIMENSIONS (WxHxD)
10.5” x 5.7” x 12” (267 x 145 x 305 mm)
PEAK CURRENT (Inrush)
30 A max (inrush limited to one cycle at 30A).
SOLDER IRON TEMPERATURE CONTROL
70% - 99% of power line (100W max).
MODEL 1653A
AC INPUT
120 VAC, 60Hz, 300 VA*
OPERATING TEMPERATURE RANGE
0°C to +40°C.
STORAGE TEMPERATURE
-30°C TO +60°C.
WEIGHT
12 lb (5.5 kg).
DIMENSIONS (WxHxD)
5.5” x 6.5” x 10.5” (140 x 165 x 267 mm).
NOTE: Specifications and information are subject to change
without notice. Please visit www.bkprecision.com for the most
current product information. *For 220V input, order model
number 1655A-220V or 1653A-220V.
5
FRONT PANEL CONTROLS
(Refer to Fig. 1 and 2)
1. POWER ON Switch.
2. POWER ON Pilot Light.
3. Function Switch.
Model 1655A
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.
CONTROLS AND INDICATORS
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.
Model 1653A
Alternate action pushbutton switch selects function of meter.
Push once to latch button in AMPS (in) position. Push again to
release button to VOLTS (out) position. The following
selections are available:
VOLTS. Connects meter to measure voltage at ISOLATED
OUTPUT. Use 0-150 VOLTS scale on meter. Voltage is
adjustable with AC Volts control.
AMPS. Connects meter to measure current of ISOLATED
OUTPUT. Use 0-2 AMPS scale on meter.
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
6. ISOLATED OUTPUT Receptacle(s). Isolated,
variable ac voltage outlet(s). The equipment under test
plugs in here. Single outlet on Model 1653A. Dual
outlets on Model 1655A.
7. *Leakage Probe. With LEAKAGE function selected,
touching probe tip to exposed metallic parts of
equipment under test checks power line leakage.
8. *SOLDER TEMP Control. Full counterclockwise
rotation turns off soldering iron outlet on rear panel.
Initial clockwise rotation turns on outlet at standby
(warm) temperature. Further clockwise rotation
increases soldering iron temperature. Temperature
adjustment is tapered, allowing fine adjustment of “hot”
temperature at upper end of adjustment range. This
control is completely independent of the POWER ON
switch.
9. *Solder Temp Pilot Light. Lights whenever soldering
iron outlet on rear panel is powered.
REAR PANEL CONTROLS
(Refer to Fig. 3 and 4)
10. AC Power Cord.
*=Model 1655A Only.
11. Fuse.
Model 1655A
4A fuse protects auto-transformer against excessive output
current at low voltages which may not trip the input
circuit breaker.
Model 1653A
3A line fuse protects against excessive input current. An
internal 3A fuse protects against excessive output current
at low voltages which may not blow the input fuse.
12. *Circuit Breaker. 3.15A circuit breaker protects against
excessive input current. Remove overload and push to
reset.
13. *Soldering Iron Outlet. AC outlet for soldering iron. Duty
cycle, and thus temperature, is variable with SOLDER
TEMP control on front panel. This outlet is intended only
for non-transformer type soldering irons rated at 100 watts
or less.
*=Model 1655A Only
7
Figure 1. Front Panel Controls and Indicators, Model 1655A
8
Figure 2. Front Panel Controls and Indicators, Model 1653A
9
Figure 3. Rear Panel Controls and Indicators, Model 1655A
10
Figure 4. Rear Panel Controls and Indicators, Model 1653A
11
OPERATING INSTRUCTIONS
PRECAUTIONS
SAFETY
The Model 1655A and 1653A AC Power Supplies are sources
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 1655A 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 1655A,
the 130-150 volt portion of the VOLTS scale is red as a reminder
that caution should be observed.
CAUTION
equipment.
12
Figure 5. Observe Caution Above 130V.
13
MAXIMUM OUTPUT CURRENT
NEVER EXCEED THE MAXIMUM OUTPUT CURRENT
RATING OF THE UNIT (Table 1). Excessive output current
can damage the variable auto-transformer.
Keep output current as low as possible; power only one piece
of equipment at a time. Use the ISOLATED OUTPUT only for
the equipment under test – not for the test equipment.
It is very important to observe the maximum current derating
(Table 1) above 130 volts, and to allow sufficient cooling time
when operating Model 1655A in the intermittent duty region.
Even at low voltages, the maximum output current should
never exceed 4 amps for Model 1655A or 2 amps for Model
1653A. Higher current may damage the variable autotransformer where the brush contacts the winding. A 3.15A
circuit breaker limits maximum input current to Model 1655A,
while a 3A fuse is used for Model 1653A. Additionally, output
fuses limit the output of the 1655A to 4 amps and the 1653A to 3
amps at low voltages that would not open the input protective
device. Never bypass the circuit breaker or fuses, or replace fuses
with a higher value.
Remove the overload to reset the circuit breaker or replace a
fuse. Turn off the unit when connecting or disconnecting
equipment from the ISOLATED OUTPUT receptacle(s).
CAUTION
For Model 1655A, the red portion of the 0-4A scale of the
meter indicates the caution zone (over 3A). This is a reminder
that only intermittent duty operation is permitted.
For Model 1635A, the output current should not exceed 2 amps
for continuous duty or intermittent duty operation. The full scale
meter indication of 2A is a reminder that this is the maximum
permissible output current.
14
Table 1. Maximum Output Current Derating.
Figure 6. Maximum Current Considerations.
15
Troubleshooting: Use As Isolation Transformer OPERATING INSTRUCTIONS
TROUBLESHOOTING: USING THE AC POWER SUPPLY AS ISOLATION TRANSFORMER
THE HAZARD
Most equipment with a 2-Wire Plug is Transformerless
Most recent television receivers and other consumer products
such as stereo amplifiers, tuners, tape decks, etc. do not contain
an isolation transformer. Such products often have a plastic or
wood cabinet which completely insulates the chassis and prevents
the user from touching it. However, when the cabinet is removed
for servicing the product, the chassis is exposed and may become
an electrical shock hazard to the service technician.
Bridge Rectifier Transformerless Equipment
One of the most commonly used types of power supply circuits
in television receivers and audio equipment is the transformerless
full wave bridge rectifier shown in Fig 7. In such cases, the
chassis is always “hot”, regardless of which way the 2-wire ac
plug is inserted. Touching a “hot” chassis is hazardous and can
cause fatal electrical shock.
Just because a unit uses a polarized power plug does not
guarantee safety. Some equipment with a bridge rectifier uses a
polarized power plug, and as mentioned above, always has a
WARNING
“hot” chassis.
Transformerless Half-Wave Rectifier Equipment
Another commonly used transformerless power supply circuit
is a half-wave rectifier where one side of the ac power line
connects directly to the chassis (also shown in Fig. 7). Unless the
equipment is equipped with a polarized plug to prevent insertion
the “wrong” way, the chassis may be “hot” (120VAC with
respect to earth ground) and cause an electrical shock if touched.
Other Transformerless Hazards
Equipment with voltage doubler power supplies may also be of
the “hot Chassis” variety and pose the same safety hazard. In
fact, and equipment with a 2-wire ac power plug should be treated
as hazardous “hot” chassis type and the safety precautions listed
on the next page should be taken.
Test Equipment Damage Hazard
In addition, to the electrical shock hazard if the “hot” chassis is
touched, there is also a high probability of damaging any acpowered test equipment used to service the equipment. Most test
equipment with a 3-wire power cord, such as oscilloscopes and
signal generators, have an earth ground chassis (connected to
earth ground through the third wire of the ac power plug).
Touching the ground lead of any such test equipment probe to a
“hot” chassis shorts the hot side of the power line through the
ground lead and instrument. Since the path through the
instrument is intended only as a signal ground, the excessive
current of a direct power line short may cause extensive damage
to the test equipment or to the equipment under test.
16
Figure 7. Servicing “Hot Chassis” Equipment Can Pose a Serious Shock Hazard.
17
THE SOLUTION
Don’t Ground the Chassis
Simply connecting a test lead from the chassis to a good earth
ground is not a satisfactory solution. If the chassis is “hot”, this
places a direct short from the “hot” side of the power line to earth
ground. Hopefully, this would only trip the circuit breaker for the
wall outlet. But a wall outlet is a very high energy source, and
before the circuit breaker is tripped, the grounding test lead may
“weld” or “disintegrate”, or severe damage may occur to the
equipment under test.
Use An Isolation Transformer
For servicing “Hot Chassis” equipment, always connect an
isolation transformer between the wall outlet and the equipment
under test. The Model 1655A or 1653A AC Power Supply
includes such an isolation transformer, among its many other
features.
As shown in Fig. 8, when an isolation transformer is used, the
chassis of the equipment under test is electrically isolated from
both sides of the power line. The chassis of the equipment under
test may not be grounded by connecting a test lead from the
chassis to a convenient earth ground (such as an earth ground
terminal of the test equipment).
Summary
Any piece of equipment with a 2-wire power plug may be the
“hot chassis” type, even if it is equipped with a polarized plug.
There is not disadvantage to using an isolation transformer, even
if the equipment under test already includes its own isolation
transformer. Therefore, for safety, treat all equipment with a 2-
wire power cord as “hot chassis” and use the ISOLATED
OUTPUT of the 1655A or 1653A AC Power Supply for servicing
such equipment.
PROCEDURE
(refer to Fig. 9)
1. Turn off the 1655A or 1653A AC Power Supply and set
AC Volts control to MIN.
2. Connect the power plug of the ac power supply to a 120
volt, 60 Hz ac wall outlet. The wall outlet must be the 3wire type with the third wire returned to a good earth
ground.
3. Connect any ac powered test equipment to be used to an
ac wall outlet (do not use the ISOLATED OUTPUT
receptacles of the ac power supply for test equipment).
4. Connect the ac power plug to the equipment under test to
the ISOLATED OUTPUT receptacle of the ac power
supply. This provides the isolation as shown in Fig. 8.
WARNING
CONNECT ONLY ONE “HOT CHASSIS” EQUIPMENT AT
A TIME. Unless both have an identical line-to-chassis
relationship, there is a shock hazard between two chassis.
5. Turn the POWER ON.
6. Select VOLTS function and adjust AC VOLTS control to
desired voltage (typically 120V).
7. It is recommended that the chassis of the equipment under
test be grounded with a test lead.
18
OPERATING INSTRUCTIONS Troubleshooting: Use As Isolation Transformer
Figure 8. Eliminating the Hazard of Servicing Transformerless Equipment
19
Figure 9. Using the AC Power Supply as an Isolation Transformer
20
OPERATING INSTRUCTIONS Troubleshooting: Use As Variable Voltage Source
TROUBLESHOOTING: USING THE AC POWER SUPPLY AS A VARIABLE AC VOLTAGE SOURCE
VARIABLE VOLTAGE SOURCE
Both the Model 1655A and 1653A AC Power Supplies offer
continuously variable output voltage from 0 to 150VAC. Several
applications are listed below, but the versatile instruments may be
used in any application where an ac power source of any value
from 0 to 150 volts is required, and within the maximum current
rating of the instrument.
24 VOLT APPLICATIONS
Class II industrial control equipment operates from nominal 24
volt, 60 Hz ac power. Such equipment is widely used in
industrial plants. These power supplies can be adjusted to 24
volts ac for bench servicing of the equipment.
130-150 VOLT APPLICATIONS
The ability to go higher then 130 volts is indispensable in
component and equipment testing where specifications must be
exceeded to verify designs and overvoltage margins.
TROUBLESHOOTING EQUIPMENT THAT BLOWS
FUSES
One of the problems with troubleshooting equipment with a
severe overload or short is that it repeatedly trips its circuit
breaker or blows fuses. Full power cannot be applied long
enough for normal voltage and waveform measurements to be
performed. The variable voltage feature permits operation at a
lower voltage that does not activate the protective device; testing
and troubleshooting can be performed with power applied.
Using the Model 1655A or 1653A AC Power Supply as shown
in Fig. 10, voltage can be set to 0 volt and slowly increased while
monitoring the current. Problems such as a defective circuit
breaker that open too soon are quickly spotted. If current reaches
its normal value (typically, about 70% of the fuse of protective
device rating) at a low voltage such as 20 volts, there is a major
short in the power supply or one of the main power distribution
circuits. If current increases to its normal value more gradually,
allowing voltage to approach 100 volts or more, an overload in
one of the circuits is probably the cause. Current that increases
sharply above a certain voltage may indicate electrical breakdown
or arcing within a component. Voltage or current measurements
in various circuits (see Fig. 10) while varying the input voltage
can help isolate the fault.
INPUT VOLTAGE SPECIFICATION TESTING
Most ac powered equipment is specified to operate over a
range of input voltage such as 120VAC ±10%. Complete
performance testing cannot be conducted without a variable ac
source. Some testing may merely consist of measuring regulated
dc voltages while varying the ac source voltage; with other tests
conducted at nominal line voltage.
LOW OR HIGH LINE VOLTAGE RELATED FAILURES
Occasionally, an equipment malfunctions only during
conditions of low or high line voltage. Troubleshooting of such
problems is almost impossible without a variable ac voltage
source. Either Model 1655A or 1653A AC Power Supply serves
as a variable ac voltage source.
21
Troubleshooting: Use As Variable Voltage Source OPERATING INSTRUCTIONS
Figure 10. Using the Variable Voltage Feature to Troubleshoot Equipment with Short Circuit
22
OPERATING INSTRUCTIONS Troubleshooting: Load Measurement
TROUBLESHOOTING: USING THE AC POWER SUPPLY TO MEASURE ELECTRICAL LOADS
LOAD MEASUREMENT PROCEDURE
Measurement of electrical load is extremely simple when using
the Model 1655A or 1653A AC Power Supply as the power
source. Refer to Fig. 11. The built-in meter may be switched to
measure the voltage and current being delivered to the equipment
under test. Multiplying the voltage times the current give the
electrical load in volt-amps.
For Model 1655A the calculations is not even required if the
measurement is made at the standard value of 120 volts. The
0-2A and 0-4A current scales are also calibrated as direct reading
0-24VA and 0-480VA scales.
NOTE
The VA scales are accurate only at 120 volts. At other voltages,
use the 0-2A or 0-4A current scales and calculate the electrical
load by multiplying output voltage times output current.
SERVICING APPLICATIONS
An initial check of electrical load can often give a clue to the
problem when troubleshooting electronics equipment. If the
equipment under test is drawing considerably less current than
normal, perhaps one of the power supply voltages is absent,
disabling several circuits. If current is higher than normal, a
transistor or other component may be shorted. If current remains
higher than normal after other faults have been corrected, a leaky
filter capacitor is suspected. Such problems should be corrected
to prevent another impending failure.
The normal electrical load or current drain for the equipment
under test is usually specified in its servicing literature. If that
information is not available, the normal current drain is typically
60% to 80% of the rated current of the circuit breaker or line fuse.
DESIGN APPLICATIONS
The design goals of any ac powered electronic product include
input power requirements. Using the ac power supply as the
power source for breadboard and prototype units provides
continuous monitoring of electrical load for various circuit
configurations, at various input voltages, and at various
temperatures.
PRODUCTION TESTING
Final testing of electrical and electronics equipment nearly
always includes monitoring of electrical load in all modes of
operation. The B+K Precision ac power supplies provide both
variable voltage and electrical load measure meant capabilities
needed in such a test station.
ENERGY EFFICIENCY
Energy efficiency has become an important consideration in
equipment selection. Equipment with the least electrical load is
the most energy efficient. The electrical load of similar products
can be compared side by side, demonstrating energy efficiency to
a customer in terms readily understood by a layman.
23
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