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Lester 33367 Technician Service Manual

Made by: Lester
Type: Technician Service Guide
Category: Battery Charger
Pages: 12
Size: 0.42 MB

 

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Technician Service Guide                                                                                                                               33367B

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PORTABLE SCR REGULATED

BATTERY CHARGER

TECHNICIAN SERVICE GUIDE

PLEASE SAVE THESE IMPORTANT SAFETY AND OPERATING INSTRUCTIONS

To be able to troubleshoot safely and effectively, it is important

 to read this guide COMPLETELY before beginning any tests.

LOOK FOR THIS SYMBOL TO POINT OUT SAFETY PRECAUTIONS. IT  MEANS:

BECOME ALERT YOUR SAFETY IS INVOLVED.

  IF YOU DO NOT FOLLOW THESE

SAFETY INSTRUCTIONS, INJURY OR PROPERTY DAMAGE CAN OCCUR.

CAUTION:  REPAIRS BY QUALIFIED

PERSONNEL ONLY.  NOTE:  MODIFYING THIS
CHARGER FOR USE OTHER THAN THAT FOR
WHICH IT WAS INTENDED, REPAIRS BY
PERSONS NOT QUALIFIED, OR NOT USING
ORIGINAL EQUIPMENT REPLACEMENT PARTS
WILL VOID THE MANUFACTURER'S WARRANTY
AND LIABILITY.  INCORRECT REASSEMBLY
MAY RESULT IN A RISK OF ELECTRIC SHOCK
OR FIRE.

CAUTION:  DO NOT EXPOSE CHARGER TO

WATER, RAIN OR POWERWASH.

DANGER:  HAZARD OF ELECTRIC SHOCK!

ALWAYS UNPLUG THE ELECTRICAL CORDS,
FIRST FROM THE AC OUTLET, AND THEN FROM
THE CHARGER RECEPTACLE, BEFORE
ATTEMPTING ANY REPAIRS OR SERVICE TO
THE CHARGER.  TURNING THE CHARGER OFF
DOES NOT REDUCE THIS RISK.

WARNING:  DO NOT OPERATE THE

CHARGER IF IT IS MALFUNCTIONING.
PERSONAL INJURY OR PROPERTY DAMAGE
COULD RESULT.

WARNING:  DO NOT TOUCH THE BATTERY

TERMINALS OR CONTACTS ON THE CHARGING
PLUG.  AN ELECTRIC SHOCK COULD RESULT.

This service guide applies to most portable style
SCR regulated charger designs but not all.  This
service guide does not cover railroad or heavy
industrial styles of chargers.  Please contact the
factory for assistance if there is doubt regarding the
appropriate service guide for a specific model of
charger.

The battery charger is, at most, one third (1/3) of the
complete system, which includes the equipment, the
batteries, and the wiring to/from and between the
batteries.  To locate and correct a problem with
certainty, initial diagnosis and testing must include
all elements of the system.  The charger is
constructed so all parts can be tested and replaced
with basic hand tools.

See the appropriate owners manual, the model
number listed on the owners manual should match
the model number on the faceplate of the charger,
for detailed installation, operating procedures and
safety precautions.  FOLLOW ALL SAFETY
PRECAUTIONS.

*33367*


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Technician Service Guide                                                                                                                               33367B

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To discourage end users from disassembling the
charger, Underwriters Laboratories and Canadian
Standards Association require that the internal
replaceable fuses be omitted from the Owners
Manual wiring diagram and parts list for specific
models.  Those parts are included in the  service
wiring diagram contained in this service guide.

PROPER CARE OF DEEP-CYCLE BATTERIES

Batteries used on industrial equipment are subjected
to severe deep-cycle duty on a daily basis.  For this
reason, it is important that only deep-cycle batteries
are used.  Although these batteries are designed to
withstand such duty, the following precautions must
be observed to obtain good performance and
maximum cycle life.

1.  New batteries should be given a full charge

before their first use because it is difficult to
know how long the batteries have been stored.

2.  Limit the use of new batteries for the first 5

cycles.  New batteries are not capable of their
rated output until they have been discharged a
number of times.

3.  Do not excessively discharge batteries.

Excessive discharge can cause polarity reversal
of individual cells resulting in complete failure
shortly thereafter.  Limited use of new batteries
will minimize the chance of cell reversal.

4.  CHECK THE LEVEL OF THE ELECTROLYTE

IN CONVENTIONAL LIQUID ELECTROLYTE
LEAD ACID BATTERIES MONTHLY.
MAINTAIN THE PROPER ELECTROLYTE
LEVEL BY ADDING WATER WHEN
NECESSARY.  Electrolyte levels lower during
discharge and rise during charge.  Therefore, it
is mandatory that water be added to cells ONLY
when they are fully charged; do not overfill.  Old
batteries require more frequent additions of
water compared to new batteries.

5.  Keep tops of batteries clean and dry to prevent

excessive self-discharge.  Keep battery
terminals reasonably tight.

6.  Sulfation results when batteries in storage are

not maintained in a charged, active state.
Internal self-discharge can bring about the start
of this condition in as little as three days in warm
temperatures.  Batteries allowed to sit
unmaintained in storage will self-discharge,
sulfate to various degrees and lose capacity.
Repeated charging will generally result in the
recovery of most of the battery’s capacity,
though some permanent loss can be expected.

BATTERY TYPES

Battery manufacturers frequently use the same
battery cases for different battery types.
Replaceable liquid electrolyte deep-cycle batteries
have removable caps.  Water electrolyzed by
discharging and charging the battery is replaced
through these openings.

Gel cell and sealed “maintenance-free” deep-cycle
batteries are generally distinguished by non-
removable cell caps.  The physical appearance of
the battery case is frequently the same as that of a
replaceable liquid electrolyte battery though the cell
caps are generally not removable.

Refer to the battery manufacturer’s information
panel on the battery case to determine the type of
battery you have.  If the information panel is missing
or not legible, do not use the battery.  Refer to your
dealer if you do not understand what type of battery
you are using and have them set the “BATTERY
TYPE” switch on the charger accordingly, if
equipped.

The “BATTERY TYPE” switch is a two-position slide
switch visible on the front of the charger.  Using a
small screwdriver, slide the switch from one setting
to the other through the opening.  Take care not to
damage the switch when moving it to the desired
setting.

PERSONAL PRECAUTIONS

1.  Someone should be within range of your voice

or close enough to come to your aid when you
work near a lead-acid battery.

2.  Have plenty of fresh water and soap nearby in

case battery acid contacts skin, clothing or eyes.

3.  Wear complete eye and clothing protection.

Avoid touching eyes while working near
batteries.

4.  If battery acid contacts skin or clothing, wash

immediately with soap and water.  If acid enters
eye, immediately flood eye with running cold
water for at least 10 minutes and get medical
attention immediately.

5.  NEVER smoke or allow a spark or flame in the

vicinity of batteries.

6.  Be extra cautious to reduce risk of dropping a

metal tool onto battery.  It might spark or short
circuit battery or other electrical part that may
cause explosion.


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Technician Service Guide                                                                                                                               33367B

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7.  Remove personal metal items such as rings,

bracelets, necklaces and watches when working
with a lead-acid battery or charger.  A lead-acid
battery can produce  a short-circuit current high
enough to weld a ring or the like to metal,
causing a severe burn.

8.  NEVER allow a battery to freeze and NEVER

attempt to charge a frozen battery.

CHARGER TEST PROCEDURES

Disconnect both the AC and DC charger cordsets.
Remove the screws on each side of the charger and
lift the cover off.  Refer to the service wiring diagram
in this service guide and compare to the charger
under test to locate the described test points.  Make
sure that all the charger’s internal connections are
secure and tight.

SECTION

MALFUNCTION SYMPTOM

PAGE

1

Charger Does Not Turn On

3

A

Indicator lights do not
illuminate after connections
to AC and battery are made.

3

B

Indicator lights illuminate but
charger does not produce
output.

5

C

Indicator lights illuminate,
charger produces output but
ammeter does not deflect.

6

2

Charger Does Not Turn Off

6

A

Does not turn off.

7

B

Turns off too soon or runs
too long.

7

3

Transformer Testing

8

A

Test Output Coil

8

B

Test Auxiliary Coil

8

4

SCR Testing

9

5

Charger AC Circuit
Breaker Trips/Fuse Blows

10

6

Charger DC Circuit
Breaker Trips/Fuse Blows

11

7

Building Circuit Breaker
Trips/Fuse Blows

11

8

Factory Assistance

12

SECTION 1 - CHARGER DOES NOT TURN ON

The electronic timer kit is powered by the battery
and/or the AC line voltage and will not operate
unless powered by the proper DC battery voltage
and polarity and/or AC line voltage.  The minimum
amount of DC voltage required for the charger to
recognize a battery is connected varies by model.
Table 1 will provide general guidelines for testing but

may not represent the actual minimum voltage,
which may be lower.

Charger Nameplate

DC Voltage

Typical DC Voltage

Required

12

8

24

16

36

25

48

33

Table 1

Inspect and test for good AC and DC fuses/circuit
breakers before proceeding with this test.  If either
the AC or DC fuse is blown or circuit breaker has
tripped, proceed to the appropriate section for the
AC or DC protection device involved.

PART A

Indicator light(s) do not illuminate after
connections to AC line voltage and battery
system are made.

Measure and record battery system DC voltage
at battery posts of machine.

Connect the positive (+) voltmeter lead to the
positive (+) battery system post and the Negative  (-)
voltmeter lead to the negative (-) battery system
post.  Reread the charger nameplate information for
the specified DC VOLTS and verify the battery
system has the proper DC voltage for the charger.

If battery maintenance has recently been performed,
check the battery system to determine if a battery
has been installed reverse polarity.  A common error
is to install one or more 6-volt batteries in a battery
pack in reverse polarity.

Measure and record battery DC voltage at
charging receptacle.

If no DC voltage is measured or the DC voltage
measured is lower than the DC voltage measured at
the batteries, repair or replace charging wires,
attachments, and circuitry in equipment.

Measure and record battery DC voltage inside
charger case.

With both AC cord and charging plug  disconnected,
remove the cover from the charger and refer to the
wiring diagram for that model of charger.  Connect
the positive voltmeter lead to the same point inside
the charger where the WHITE (+) DC cord lead
connects.  Connect the negative voltmeter lead to


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Technician Service Guide                                                                                                                               33367B

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the same point inside the charger where the BLACK
(-) DC cord lead connects.  Test points E & F on the
service wiring diagram.  Connect the DC output cord
to the equipment charging receptacle and record the
DC voltage measured.  See figure 1.

Figure 1

The DC voltage measured at these test points must
be the same as the battery system voltage
measured at the batteries, before the charger can
operate.  If the voltage measured is zero, or lower
than the results of prior measurements, then replace
the DC charging cordset and/or the equipment
charging receptacle and retest.

Measure and record battery DC voltage at
electronic timer kit.

If the DC voltage measured at test points E & F are
correct, carefully remove the timer kit edge
connector or flag terminals attached to the DC sense
leads of the control cable from the electronic timer.
Carefully examine the control cable assembly,
electronic timer assembly connector and compare to
the wiring diagram for the charger model.  The same
DC voltage at test points E & F must be present at
the connector contacts of the RED (+) positive (pin 9
of the edge connector) and BLACK (-) negative (pin
5 of the edge connector) control cable assembly
sense wires, as shown on the service wiring
diagram.  If no DC voltage is measured or the DC
voltage measured is lower than the DC voltage
measured at test points E & F, repair or replace the
control cable assembly.  See figure 2.

Figure 2

If the DC voltage measured at the electronic timer
edge connector or flag terminals is correct, testing of
the AC line voltage must be performed.

DANGER:  HAZARD OF ELECTRIC SHOCK!

THE FOLLOWING TESTS REQUIRE THE
CHARGER TO BE CONNECTED TO A LIVE AC
OUTLET.  FOLLOW ALL ELECTRICAL SAFETY
PRECAUTIONS TO AVOID ELECTRIC SHOCK!

Inspect and test for proper AC supply voltage at
the outlet.

Disconnect the DC output cord from the equipment
charging receptacle.  Verify the charger AC power
plug is disconnected and measure the AC line
voltage at the outlet with a suitable meter.  If no
voltage is measured, test additional outlets until AC
voltage is measured. Read the charger nameplate
for the required nominal AC voltage  and verify this
matches the measured AC voltage at the outlet.
Make sure the charger voltage selector switch is set
to the correct position, if equipped.

Verify charger AC input circuit wiring is correct.

Locate the charger nameplate model number and
verify it and the model number listed on the wiring
diagram specific for the model being serviced match.
With the charger cover removed, inspect and verify
the charger is wired correctly according to the wiring
diagram.


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Technician Service Guide                                                                                                                               33367B

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Measure and record the AC line voltage at the
charger power switch.

Connect the AC power plug to a live electrical outlet
with the proper AC voltage per charger nameplate
and, if equipped, voltage selector switch setting.
Locate the WHITE and BLACK AC power cord lead
connections to the power switch.  Attach leads from
a suitable AC voltmeter to these AC cordset
connections and verify the presence of proper AC
voltage.  If no voltage is measured, replace the AC
cordset with the replacement service part specified
on the parts list for this specific model charger and
retest.

Measure and record the AC line voltage at the
AC fuse(s) or circuit breaker(s).

If the presence of AC voltage on the cordset is
verified, move the AC voltmeter test leads to the
transformer side of the AC fuse(s) or circuit
breakers(s).  Test points A and B on the service
wiring diagram.  See figure 3.

Figure 3

If no AC voltage is measured on the transformer
side of the AC fuse(s) or circuit breaker(s), test
points A and B, remove the AC power plug from the
AC outlet.  Test for continuity through the power
switch, AC voltage selector switch and AC
fuse(s)/fuseholder(s) or circuit breaker(s).  Replace
all parts measuring no continuity with replacement
service part(s) specified on the parts list for this
specific model charger and retest.

If the correct AC voltage is measured on the
transformer side of the AC fuse(s) or circuit
breaker(s), proceed to 

Section 3, Part B, Test for

correct transformer auxiliary coil voltage.

  If the

transformer auxiliary coil test indicates a failed
transformer, test for correct charger indicator light
operation after transformer replacement.  If the

transformer auxiliary coil test indicates proper AC
voltage output or the indicator lights still do not
illuminate after transformer replacement, the
electronic timer must be repaired or replaced.
Replace the electronic timer with the replacement
service part specified on the parts list for the specific
model of charger being serviced and confirm
indicator light illumination.

WARNING: ALWAYS TEST SCRs  BEFORE
REPLACING AN ELECTRONIC TIMER.  DAMAGE
AND SUBSEQUENT FAILURE WILL OCCUR TO
ALL ELECTRONIC TIMERS INSTALLED IN A
CHARGER THAT CONTAINS A SHORTED
ANODE TO GATE SCR, IF CONNECTED TO AC
POWER.

For SCR testing instructions see 

Section 4, SCR

Testing Procedure.

Part B

Indicator lights illuminate but charger does not
produce output.

Charger models with an ammeter will show no
deflection, models without an ammeter but with a
fault light indicator may show an overvoltage fault
condition.

THIS MALFUNCTION SYMPTOM MAY BE DUE
TO FACTORS OTHER THAN THE CHARGER’S
PERFORMANCE.  TO HELP ISOLATE THE
PROBLEM, IT IS OFTEN NECESSARY TO USE
THE CHARGER ON A DIFFERENT SET OF
BATTERIES AND THE ORIGINAL SET OF
BATTERIES ON ANOTHER CHARGER.

Test for battery voltage increase.

This condition may be caused by a high resistance
in the DC charging circuit  due to a bad connection
or batteries.  Using an appropriate DC voltmeter,
measure and record the DC voltage across the
batteries without the charger connected.  Connect
the charger AC power plug to a live AC outlet and
the DC output plug to the equipment charging
receptacle.  Note and record the initial voltage
increase measured.

Under normal operation the battery system voltage
will usually increase one or two volts when the
charger first turns on.  After the initial increase the
battery voltage will gradually rise over time to it’s
final on-charge voltage.  The final on-charge voltage
will vary depending on battery age, condition,
temperature and other factors.  Conventional wet
lead-acid batteries will usually reach an on-charge
votlage of 2.5 volts per cell or higher, while sealed
batteries usually do not exceed 2.4 volts per cell.


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If the measured voltage increase on the batteries
indicates the full on-charge voltage when the
charger turns on, the source of the high resistance
must be corrected to obtain proper charging.
Rework bad connections on batteries or replace bad
battery cables and/or batteries.

If the measured voltage increase on the batteries
indicates normal rise, perform the same test where
the WHITE (+) DC cord lead connects (test point E)
and the BLACK (-) DC cord lead connects (test point
F) in the charger,  see figure 1.  If the measured
voltage increase indicates the full on-charge voltage
when the charger turns on, correct the source of the
high resistance.  Repair or replace the charger DC
cordset, equipment charging receptacle and/or
equipment wiring.

Inspect and test charger DC circuit.

If the measured battery system voltage increase on
the batteries and at charger test points E and F
indicate normal operation, disconnect both the AC
power plug from the outlet and the DC plug from the
equipment charging receptacle.

Inspect and make sure all connections to the
fuse/circuit breaker, shunt and ammeter, if equipped,
are secure and tight.

If the charger being serviced has an ammeter and
the needle did not deflect but the charger passed the

Test for battery voltage increase”

, replace the

ammeter with the replacement service part specified
on the parts list for the specific model of charger
being serviced and retest.

If the charger being serviced does not have an
ammeter and the charger passed the “

Test for

battery voltage increase” 

or replacement of the

ammeter did not correct the problem, measure
continuity of the charger’s DC circuits.

Place one test lead of continuity meter where the
WHITE (+) DC cordset lead connects (test point E)
and the other test lead of the continuity meter on the
SCR side of the shunt, to measure the positive
output side.  If continuity is not measured, rework
connections to the shunt and/or replace failed shunt
and retest.

To measure the negative output side, place one test
lead of the continuity meter where the BLACK (-) DC
cordset lead connects (test point F) and the other
test lead of the continuity meter on the SCR side of
the DC fuse/circuit breaker.  If continuity is not
measured, rework connections to the DC fuse/circuit
breaker and ammeter, if equipped, or replace failed
DC fuse, fuseholder/circuit breaker and/or ammeter,
as needed and retest.

If the charger passes both the “

Test for battery

voltage increase”

 and “

Inspect and test charger

DC

 

circuit

” proceed to  

Section 3, Part A, Test for

correct transformer output coil voltage.

  If the

transformer output coil voltage test indicates a failed
transformer, retest charger for proper operation after
transformer replacement.  If the transformer passes
the output coil voltage test or the charger still has no
output after transformer replacement, the electronic
timer must be repaired or replaced.

WARNING: ALWAYS TEST SCRs  BEFORE
REPLACING AN ELECTRONIC TIMER.  DAMAGE
AND SUBSEQUENT FAILURE WILL OCCUR TO
ALL ELECTRONIC TIMERS INSTALLED IN A
CHARGER THAT CONTAINS A SHORTED
ANODE TO GATE SCR, IF CONNECTED TO AC
POWER.

For SCR testing instructions, see 

Section 4, SCR

testing procedure.

Part C

Indicator light(s) illuminate, charger produces
output but ammeter does not deflect.

If the charger is known to be producing output
current, by performing the 

Test for battery voltage

increase, Section1, part B

 or by measuring output

current with an external ammeter, but the charger’s
ammeter needle doesn’t deflect, replace the
ammeter with the replacement service part listed on
the parts list for the specific model of charger being
serviced.

SECTION 2 - CHARGER DOES NOT TURN OFF

This malfunction symptom may be due to factors
other than the charger’s performance, such as bad
batteries or charging larger capacity batteries than
the charger is rated for. Chargers with a fault light
will indicate a “maximum charge time exceeded”
fault.

Bad batteries may not allow the battery system to
obtain an overall gassing point voltage, which is
approximately 2.25 volts per cell.  (2.25 volts per cell
X the number of cells in the battery system = battery
system gassing point voltage) The electronic timer
monitors the batteries for a full charge condition after
the battery voltage reaches the gassing point.  Verify
the battery system is capable of reaching the
gassing point voltage.  If the batteries cannot reach
the gassing point voltage, the useful life of the
batteries has ended and replacement is required.

Verify the charger is providing the charge rate
specified on the charger nameplate, DC AMPS, at
the start of the charge cycle (battery voltage below 2
volts per cell).  If the charger does not output the
specified amount of  DC amperes, see 

Section 1,

Part B, Test for battery voltage increase 

and

Section 4 SCR Testing.  

If a lower than specified


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charge rate is noted and the findings of the 

Test for

battery voltage increase

 are normal, an SCR may

have failed.  Each charger has two SCRs.

Part A

Does not turn off.

This may be caused by a failed SCR and/or
electronic timer.  If the charger is found to be
producing a high finish charge rate, while the
batteries are at or above the typical finish voltage of
2.30 volts per cell or higher, test for a shorted anode
to gate SCR, see 

Section 4-SCR Testing

.  If an

SCR with a shorted anode to gate is found, the
electronic timer has been damaged and must also
be replaced.  Replace with the replacement service
parts specified on the parts list for the specific model
of charger being serviced and retest.  If both SCRs
test good, repair or replace the electronic timer.

Part B

Turns off too soon or runs too long.

If batteries have not been used or charged regularly,
they may be sulfated and will not produce their full
capacity.  Repeated cycles (at least 5) of a light
discharge, followed by a full charge, will generally
result in the recovery of most of the battery’s
capacity.  Do not interpret this reduced battery
capacity as being caused by the charger’s turning off
too soon.  The charger is working properly if, after
several charge cycles, the battery capacity increases
to near normal.  Sulfation occurs most often when
batteries have been stored without weekly charging.
New batteries may also be sulfated due to extended
shipment or storage time prior to sale.

As batteries age, individual cells may weaken,
causing a reduction in battery capacity.  This
condition normally results in a higher finish rate on
conventional wet lead-acid batteries and shorter
charge times for both conventional and sealed types
of batteries.  Do not interpret this shorter charging
time and reduced battery capacity as being caused
by the charger’s turning off too soon.  The battery is
aging naturally and the charger is working properly.
When the batteries will no longer perform as
required, they should be replaced.

The charger is designed to cease charging when
essentially no further electrochemical reaction is
occurring inside the battery.  The electronic timer
senses the progress of the reactions and, when
these reactions virtually cease, turns the charger off.

For conventional wet lead-acid batteries there are
two ways to test if the electrochemical reaction has
actually ceased.

1.  An accurate hydrometer can be used to

determine cessation of the electrochemical
charging reaction.  If the measured specific
gravity of several cells does not increase in
three (3) consecutive readings taken one hour
apart while the charger continues to charge, the
charger is operating too long.

2.  An accurate 5 1/2-digit digital voltmeter can be

used to determine the cessation of the
electrochemical charging reaction.  Connect the
voltmeter test leads to the positive (+) and
negative (-) posts of the battery system being
charged.  Monitor and record the on-charge
voltage at 30-minute intervals.  If the on-charge
battery voltage either begins to decrease
between 30-minute intervals or increases by
less than 0.012 DC volts in two consecutive 30-
minute intervals, the charger is operating too
long.

To test sealed or gel batteries, an accurate digital
ammeter can be used to determine the cessation of
the electrochemical charging reaction.  Break the
DC charging circuit and insert the digital ammeter in-
line with the circuit.  Monitor and record the on-
charge current at 30-minute intervals when the
battery system voltage is at or above 2.32 volts per
cell.  If the on-charge current does not decrease by
0.015 DC milliAMPS in two consecutive readings,
the charger is operating too long.

In the event of an AC power interruption when the
charger is on, the charger will automatically restart
when AC power is restored.  This power outage can
make the apparent charge time seem longer than
the actual charge time.  To check for AC power
interruptions, plug an electric clock into the same
outlet to which the charger AC cord is connected.
Charge normally and note any time difference
between the test clock time and the actual time.

If battery maintenance has recently been performed,
check the battery system to determine if a battery
has been installed reverse polarity.  A common error
is to install one or more 6-volt batteries in a battery
pack in reverse polarity.

If testing indicates the charger is turning off too soon
or operating too long, replace the electronic timer
with the replacement service part specified on the
parts list for the specific model of charger being
serviced and retest.

 

WARNING: ALWAYS TEST SCRs  BEFORE

REPLACING AN ELECTRONIC TIMER.  DAMAGE
AND SUBSEQUENT FAILURE WILL OCCUR TO
ALL ELECTRONIC TIMERS INSTALLED IN A
CHARGER THAT CONTAINS A SHORTED
ANODE TO GATE SCR, IF CONNECTED TO AC
POWER.


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Technician Service Guide                                                                                                                               33367B

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SECTION 3 - TRANSFORMER TESTING
PROCEDURE

DANGER:  HAZARD OF ELECTRIC SHOCK!

THE FOLLOWING TESTS REQUIRE THE
CHARGER TO BE CONNECTED TO A LIVE AC
OUTLET.  FOLLOW ALL ELECTRICAL SAFETY
PRECAUTIONS TO AVOID ELECTRIC SHOCK!

The transformer primary coil must be energized by
the AC voltage and frequency specified on the
charger nameplate in order to obtain accurate test
results.  Verify the specified voltage is present at test
points A and B on the service wiring diagram, see
figure 3.  If no voltage or an incorrect amount of
voltage is measured, testing of the AC circuit is
required before transformer testing can be
performed.  Begin the AC circuit testing with 

Inspect

and test for proper AC supply voltage at the
outlet.

Part A

Test for correct transformer output coil voltage.

Disconnect the AC power plug from the outlet and
the DC output plug from the equipment charging
receptacle.  Remove the cover from the charger and
disconnect both transformer output coil leads from
the heatsink plates.  For personal safety, make sure
the transformer leads are isolated and not making
contact with any components or the case of the
charger.  Attach the test leads of a suitable AC
voltmeter to the transformer output coil leads, tests
points C and D on the service wiring diagram, see
figure 4.  Reconnect the AC power plug to a live
outlet.  Measure and record the AC voltage present
at the transformer output coil leads and compare to
the values in table 2.

Figure 4

If the measured AC voltage indicates the
transformer has failed, indicated by significantly
lower voltage readings, replace the transformer with
the replacement service part specified on the parts
list for the model charger being serviced.

Part B

Test for correct transformer auxiliary coil
voltage.

Disconnect the AC power plug from the outlet and
the DC output plug from the equipment charging
receptacle.  Remove the cover from the charger.
Carefully remove the timer kit edge connector or flag
terminals attached to the DC sense leads of the
control cable from the electronic timer.

Before measuring the auxiliary coil output voltage,
inspect and test for continuity the transformer
auxiliary coil lead extensions. Also, inspect the
contacts in the edge connector for distortion,
corrosion or any condition that would prevent
electrical contact with the pads on the electronic
timer.  Measure continuity of the transformer
auxiliary coil circuit by placing the test probes of a
continuity meter on pins 4 and 6 of the electronic
timer edge connector.  If no continuity is measured
between the two points, rework or replace  the
transformer extension leads, edge connector and/or
transformer, as needed.

Attach the test leads of a suitable AC voltmeter to
the auxiliary lead contacts in the edge connector,
pins 4 and 6 on the service wiring diagram.  See
figure 5.  Reconnect the AC power plug to a live
outlet.  Measure and record the AC voltage present
at the specified edge connector pins and compare to
the values in table 2.

Figure 5


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Technician Service Guide                                                                                                                               33367B

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If the measured AC voltage indicates the
transformer has failed, indicated by significantly
lower voltage readings, replace the transformer with
the replacement service part specified on the parts
list for the model of charger being serviced.

Charger

Nameplate

DC Voltage

No Load

Output Coil

AC Voltage*

No Load

Auxiliary Coil

AC Voltage

12

28-44

24

56-90

36

90-126

48

120-168

24-32

Note: The voltage readings are approximate and
transformer failure is indicated when the
measured AC voltages are SIGNIFICANTLY
LOWER than the listed values.

(*) The wide AC voltage range is the result of
various AC line voltages that many charger
models have been designed to operate on.

Table 2

If it should become necessary to replace a terminal
on one of the transformer leads, the new terminal
must be crimped AND soldered.

SECTION 4 - SCR TESTING

The feedback  control design of the charger makes it
possible for one SCR in the SCR assembly to not
function and the charger to still have some output.
This condition can be detected by noting the
temperature of the separate SCRs and replacing the
complete assembly if one of the SCRs feels cold
and the other hot.  This condition may also suggest
it’s presence by continual melting of the DC fuse,
see 

Section 6 - Charger DC Circuit Breaker

Trips/Fuse Blows 

for additional information.

An SCR can fail in a shorted or open mode.  Shorted
SCRs can be detected by measuring the resistance
between the legs of the SCR with an ohm-meter.  An
SCR that is shorted Anode to Cathode will cause the
DC circuit breaker to trip or fuse to blow, see

Section 6 - Charger DC Circuit Breaker
Trips/Fuse Blows

 for more information.  An SCR

with a shorted anode to gate can be detected by
measuring the resistance between the anode to
gate.  To do so, first disconnect the charger AC
power plug from the outlet and the DC output cord
from the equipment charging receptacle.  Remove
the charger’s cover and carefully remove the control
cable edge connector from the electronic timer.

Locate the in-line bullet connectors on the brown
leads (gate) of the SCRs and disconnect, see figure
6.

Figure 6

Using an ohm-meter, measure the resistance
between between the brown gate lead of the SCR
and the heatsink plate (SCR anode).  Test each
SCR separately.  Connect the positive (+) lead of the
ohm-meter to the heatsink plate (anode) of one
SCR.  Connect the negative (-) lead of the ohm-
meter to the brown gate lead for that same SCR.
The resistance for a good SCR should be about 20
megohms.  Reverse the leads of the ohm-meter and
test the SCR again.  Resistance for a good SCR
should be in the megohms.

The resistance of a failed SCR, regardless of ohm-
meter polarity, will be about 50 ohms.

If an SCR with a shorted anode to gate is located,
the electronic timer has been damaged and must be
repaired or replaced with the SCR assembly.

WARNING: ALWAYS TEST SCRs  BEFORE
REPLACING AN ELECTRONIC TIMER.  DAMAGE
AND SUBSEQUENT FAILURE WILL OCCUR TO
ALL ELECTRONIC TIMERS INSTALLED IN A
CHARGER THAT CONTAINS A SHORTED
ANODE TO GATE SCR, IF CONNECTED TO AC
POWER.

DANGER:  HAZARD OF ELECTRIC SHOCK!

THE FOLLOWING TEST REQUIRES THE
CHARGER TO BE CONNECTED TO A LIVE AC
OUTLET.  FOLLOW ALL ELECTRICAL SAFETY
PRECAUTIONS TO AVOID ELECTRIC SHOCK!


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The SCRs may be electrically tested for an open
condition by turning them on one at a time manually
while the charger is energized. To do so, first
disconnect the charger AC power plug from the
outlet and the DC output cord from the equipment
charging receptacle.  Remove the charger’s cover
and carefully remove the control cable edge
connector from the electronic timer.

Before testing the SCRs, inspect and test for
continuity the gate lead of each SCR.  (Note: The
SCRs in some charger designs are soldered directly
into the printed circuit board and will not have gate
leads.) First, inspect the contacts in the edge
connector for distortion, corrosion or any condition
that would prevent electrical contact with the pads
on the electronic timer.  Measure the continuity of
each BROWN gate lead by placing one test probe
from the continuity meter on the brown gate lead at
the SCR.  Place the remaining test probe on the
appropriate contact in the electronic timer edge
connector, pins 1 and 2 on the service wiring
diagram.  Repeat the same test on the remaining
SCR gate lead.  If no continuity is measured on the
gate lead(s), rework or replace the edge connector,
in-line bullet connector and/or wiring, as needed.

Each SCR may be turned on manually by
connecting a 3 volt  battery to the SCR. (Note: Some
SCRs may require only 1.5 volts DC to forward
bias.)  Connect the AC power plug to a live outlet,
connect the DC output plug to a fully charged battery
pack and set the power switch to AUTO.  Connect
the negative (-) end of the battery to the output side
of the SCR (cathode) by attaching to  the shunt, test
point E on the service wiring diagram, or the positive
DC cordset connection. Momentarily touch the lead
from the positive (+) end of the battery to the gate
lead of each SCR in the electronic timer edge
conenctor, pins 1 & 2 on the service wiring diagram.
See figure 7.  Do not continue this for more than a
few seconds as it is possible to damage the SCRs
and charger.

Figure 7

If the SCRs are good, the charger’s ammeter will
indicate current flow when each SCR gate lead is
touched by the positive (+) end of the battery.  For
chargers without an ammeter an in-line ammeter
may be used in the DC charging circuit to test for
current flow or a DC voltmeter may be used to test
for momentary battery voltage increase.

If the ammeter does not indicate current flow for
each SCR, the SCR not causing ammeter deflection
has failed and the SCR assembly must be replaced.

SECTION 5 - CHARGER AC CIRCUIT BREAKER
TRIPS/FUSE BLOWS

Before proceeding, verify the rating of the blown
fuse is correct for the model of charger being
serviced.  If the value is lower than specified for the
charger being serviced, install a fuse of correct size
and recheck charger operation.  If the AC protection
device is a circuit breaker, the quickest and most
accurate way to eliminate the possibility of a faulty
breaker is to replace the breaker with a known good
one.

There are two modes of failure, instantaneous and
delayed blowing of the AC protection device.   If the
AC protection device allows the charger to operate
for a period of time before blowing, this is usually the
result of gradual heating of the protection device.
Inspect the connections to the circuit breaker/fuse
for signs of heat caused by a loose connection,
corrosion, physical damage or otherwise.

If the AC protection device itself passes inspection,
the most likely cause is a failed SCR.  The failure of
one SCR will force the remaining SCR to try and
produce the charger’s full output.  This results in a
high current draw on the portion of the input AC sine
wave that the remaining good SCR is rectifying.  The
higher AC current draw eventually causes enough
heating of the AC protection device to cause it to
blow.  See 

Section 4 - SCR Testing.

Instantaneous blowing of the AC protection device
indicates a direct short.  Refer to the service wiring
diagram, the only component following the AC
protection device is the transformer.  If the AC
protection device itself passes testing and
inspection, replace the transformer and retest.  If the
wiring diagram for the specific model of charger
being serviced shows any other component(s)
between the AC protection device and the
transformer, isolate each component and test with a
continuity meter for a shorted condition before
replacing the transformer.

DANGER:  REPLACE THE FUSE OR FUSE

ASSEMBLY ONLY WITH THE CORRECT FUSE
OR FUSE ASSEMBLY.  FIRE, PROPERTY
DAMAGE, AND PERSONAL INJURY CAN


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Technician Service Guide                                                                                                                               33367B

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RESULT IF THE CHARGER IS USED WITH AN
INCORRECT FUSE.

SECTION 6 - CHARGER DC CIRCUIT BREAKER
TRIPS/FUSE BLOWS

Before proceeding, verify the rating of the blown
fuse is correct for the model of charger being
serviced.  If the value is lower than specified for the
charger being serviced, install a fuse of correct size
and recheck charger operation.  If the DC protection
device is a circuit breaker, the quickest and most
accurate way to eliminate the possibility of a faulty
breaker is to replace the breaker with a known good
one.

There are two modes of failure, instantaneous and
delayed blowing of the DC protection device.   If the
DC protection device allows the charger to operate
for a period of time before blowing, this is usually the
result of gradual heating of the protection device.
Inspect the connections to the circuit breaker/fuse
for signs of heat caused by a loose connection,
corrosion, physical damage or otherwise.

If the DC protection device itself passes inspection,
confirm the DC voltage polarity from the battery
system is correct.  Disconnect the AC power plug
from the electrical outlet, remove the charger’s
cover, connect the DC output cord to the equipment
charging receptacle and measure the DC voltage
present at test points E and F on the service wiring
diagram.  See figure 1.  Verify the positive (+) is on
test point E, WHITE DC cordset lead, and the
negative (-) is on test point F, BLACK DC cordset
lead.

If the proper polarity is not measured, locate and
correct the wiring defect.  If the correct polarity is
measured at test points E and F, the cause of the
DC protection device opening may be caused by a
shorted SCR.  See 

Section 4 - SCR Testing.

DANGER:  REPLACE THE FUSE OR FUSE

ASSEMBLY ONLY WITH THE CORRECT FUSE
OR FUSE ASSEMBLY.  FIRE, PROPERTY
DAMAGE, AND PERSONAL INJURY CAN
RESULT IF THE CHARGER IS USED WITH AN
INCORRECT FUSE.

SECTION 7 - BUILDING CIRCUIT BREAKER
TRIPS/FUSE BLOWS

This condition can be caused by a charger problem,
a “weak” fuse or circuit breaker protecting the circuit,
or an overloaded circuit.  If the building AC power
fuse or circuit breaker blows, connect the charger to
other outlets (on different circuits) in the building.  If

the charger operates properly on other circuits, have
a qualified electrician check the original circuit.  If the
charger causes other fuses or circuit breakers (in the
building) to blow, the charger must be checked for a
problem.

Disconnect both the AC power plug from the outlet
and the DC output plug from the equipment charging
receptacle.  Remove the charger cover.  Locate the
charger nameplate model number and verify it and
the model number listed on the wiring diagram
specific for the model being serviced match.  Inspect
and verify the charger is wired correctly according to
the wiring diagram.

Locate and disconnect the transformer primary coil
leads from the AC fuse(s)/circuit breaker(s), test
points A and B on the service wiring diagram.  See
figure 3.   Using a continuity tester, measure the
continuity between the two flat blades of the AC
power plug, see figure 8.

Figure 8

If no continuity is measured between the two flat
blades of the AC power plug, replace the
transformer and retest.

If continuity is still measured between the two flat
blades of the AC power plug, disconnect the AC
cordset lead(s) from the on/off power switch.  Again,
measure for continuity between the two flat blades of
the AC power plug, as shown in figure 8.  If
continuity is still measured between the two flat
blades of the AC power plug, replace the AC cordset
and retest.

If no continuity is measured between the two flat
blades of the AC power plug, isolate each remaining
component (on/off power switch, AC voltage selector
switch and any additional components shown in the
wiring diagram specific for the model being serviced)
in the AC input circuit and measure for continuity.
Replace the failed component(s) that measure
continuity with the replacement service part(s)
specified on the parts list for the model charger
being serviced and retest.


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Technician Service Guide                                                                                                                               33367B

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SECTION 8 - FACTORY ASSISTANCE

Technical support is available from the factory
Monday through Friday, 8am - 4:30pm CT.

Contact may be made by the following methods:

Mail: Lester Electrical

         625 West ‘A’ Street

         Lincoln, NE 68522-1794   USA

   Attention: Service Department

Phone: (402) 477-8988

FAX: (402) 474-1769

E-mail: 

service@lesterelectrical.com

SERVICE WIRING DIAGRAM

BLACK

AC VOLTAGE *

SELECTOR

SWITCH

POWER

SWITCH

BLACK

GREEN

WHITE

100-125
200-250

VAC

INPUT

WHITE

WHITE

AC

FUSE

1b

1a

2b

2a

BROWN

BROWN

GRAY

BLACK

AC

FUSE

TRANSFORMER

SCR

BLACK

BLACK

BLACK

SCR

BLACK

1

2

3

4

9

10

11

12

SHUNT

Y

E

L

L

O

W

B

R

O

W

N

B

R

O

W

N

WHITE

DC

OUTPUT

AMMETER

40 AMP

CIRCUIT BREAKER

BLACK

BLACK

BLUE

NATURAL

BLUE

ELECTRONIC

TIMER

5

6

7

8

*SHOWN IN

100-125 VOLT

POSITION

RED

ORANGE

BLUE

BLACK

BLUE

YELLOW

BROWN

BROWN

9

7

6

5

4

3

2

1

C

E

B

A

F

D

01821

PLEASE REFER TO THE SPECIFIC DIAGRAM IN THE OWNERS MANUAL.