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3. TESTING OF COMPONENTS
a. Power Transformer (T1)
With the ac and dc circuit breakers open or OFF, open the cabinet and carefully check the line voltage
across line terminals on TB1, terminals L1 to L2 (do not confuse terminals L1 and L2 with the inductor components,
also labeled L1 and L2). If ac voltage is indicated, turn on the ac circuit breaker (CB1) and check the voltage at
terminals X1 and X5. The ac secondary voltage on the power transformer (T1) is approximately 180Vac. This can be
measured at the bottom terminal of each SCR (Q1/Q2) with a DVM.
b. Polarity Protection Diode (CR1)
If the polarity protection diode (CR1) is shorted, the battery will discharge into it. This will trip the dc
circuit breaker (CB2). With all power disconnected from the charger, disconnect the flying lead of CR1 and check
across the diode with an ohmmeter (both polarities) for a shorted condition and replace if required. A normal diode
should measure at least 10,000 Ohms in one polarity.
c. Rectifier Modules (Q1/Q2)
The SCRs (Q1/Q2) rarely fail while open. If a failure occurs in the SCRs, the breaker(s) will trip
similarly to the polarity diode (CR1). To check the device(s), remove wires from the SCR modules (Q1/Q2) and
inspect with an ohmmeter for shorted terminals. See the schematic symbol on the side of the device for terminal
connections. SCR modules usually fail because of surge voltages. Therefore, the surge suppressors (SS1, SS2)
should also be checked to determine if they are damaged or not connected.
d. Surge Suppressors (SS1, SS2)
The Metal-Oxide Varistor (MOV) type of surge suppressor is used on the input and output of the battery
charger. If an MOV surge suppressor fails during a high-energy transient it may explode. This is an obvious failure
and the part must be replaced. When the suppressor shows an infinite resistance in both directions measured with it
disconnected from the charger and has a normal appearance it can be presumed to be in good operating condition.
There is no way to test a good MOV.
e. Control Module PC Board Assembly (A1)
The voltage feedback and Current Limit circuit controls the battery charger output voltage. The feedback
voltage from the wiper of the Voltage Adjustment potentiometer to output terminal (-) is 6-7Vdc when the charger is
not in current limit. If the charger's output voltage is lower then expected, the resistors in the feedback loop should be
checked or current limit control may not be fully clockwise (CW), or the charger may be in current limit.
f. DC Voltmeter (M2)
The dc voltmeter (M2) is connected across the charger's output or the charger's input before the dc
breaker (CB2) depending on the position of the Voltage Check switch (SW2). The meter will only indicate if the
charger's input power is applied, and ac breaker (CB1) is on. If there is no display, check for 9 Volts at pins 2 and 3
(around 9.5Vdc). The input signal is connected to pins 14 and 15 (output Volts/100). Calibrate the dc voltmeter (M2)
by adjusting the potentiometer located on the meter itself. If the meter calibration is in doubt, check by using a
precision digital multimeter.
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