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Technician Service Guide                                                                                                                               33367B

10

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

Summary of Contents for 33367

Page 1: ...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...

Page 2: ...ratures 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 b...

Page 3: ...equired 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 f...

Page 4: ...e 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 SHO...

Page 5: ... 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 TI...

Page 6: ... 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 re...

Page 7: ...cid 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...

Page 8: ...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 ...

Page 9: ...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...

Page 10: ...or 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 p...

Page 11: ...KER 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 charge...

Page 12: ...lectrical 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 YELLOW BROWN BROWN WHITE DC OUTPUT AMMETER 40 AMP CIRCUIT BREAKER BLACK BLACK BLUE NATURAL BLUE ELECTRONIC TIMER 5 6 7 8 SHOWN IN 100 125 VOL...

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