Exide Technologies JA5009-00 - Manual (Page 13)

9
g. Control Module PC Board Assembly (A1)
One preliminary note that should be kept in mind: The action of the overall feedback circuit controls
the battery charger output voltage so that the feedback voltage from the slider of the "FLOAT ADJUST"
potentiometer (R3) to the control module board matches the 6.4 Volt reference voltage on the module.
Measure this voltage and if it is not approximately 6.4 Volts the feedback circuit or related circuits are not
functioning. Proceed as follows using the GROUND ISOLATED oscilloscope described in Section III, 2, f,
2 on page 8. Make the following tests in the order shown.
1. If the gate signals were not checked as described in Section III, 2, f, 2, do so at this time. If one or
more of the gate signals are absent when attempting to operate the charger in a normal manner, make the
following checks. Refer to FIGURE 1 on page 29 for component layout and test point locations on the
trigger board (A1). See schematic on page 30 for related circuit diagram.
2. Check DC voltages at test points A (+10 volts) and B (-10 volts), referred to board ground,
(GND). If either or both voltages are missing, check fuse (F1), transformer (T1), and diodes (CR1-CR4) on
the PCB for malfunction. If ok, proceed as follows.
3. The following waveform tests must be made using the oscilloscope set with vertical sensitivity set
at 2V/CM and the horizontal time base set at 5MS/CM. Compare the waveforms observed with those shown
in FIGURE 2 on page 31 for the various test points indicated.
4. Check waveform at test point C and compare with FIGURE 2. If waveform is improper, check
CR12 and CR13. Check amplified inverted waveform at test point D. If it is not present, replace IC2.
5. Check ramp pattern at test point E. If not proper, replace Q1 only with its own type, Motorola
MPSA55. Do not substitute.
6. Check the ramp with floating DC reference at test point F. If it is not present, replace IC2.
7. Check the short pulse at point G. If not present, check uni-junction transistor Q3.
8. Check waveform at point H. Note that at both points G and H, there may be multiple pulses
instead of only one pulse per 8.33 ms period. This is normal particularly if the unit is calling for maximum
output voltage. If no pulse waveform is present replace transistor Q2.
9. Check the battery charger rectified waveform by connecting the oscilloscope across the bleeder
resistor, R1, and readjusting the input sensitivity to 20 V/CM. If the unit is turned “half-on”, the waveform
will look approximately like the waveform of I of FIGURE 2.
h. Current Sensing Resistor (SH1)
1. In light current chargers, the current sensing signal is taken directly across the DC ammeter. In
chargers with 50 Amp or higher output current, the sensing resistor is a meter shunt, which also serves as the
shunt for the panel ammeter. Use a portable precision digital voltmeter and measure the voltage drop across
the current sensing resistor. With a rated current output indicated on the panel ammeter, a nominal voltage
drop of approximately 30mV (in proportion to rated current) should be observed. If the voltage drop is
higher or lower than the nominal indication, replace the ammeter or shunt and recheck the voltage drop.
j. DC Voltmeter (M2)
1. The DC voltmeter is of the 2 percent accuracy type. It is connected across the charger output to the
battery and should indicate regardless of whether or not the charger is operating or the DC breaker is ON. If
it does not, use a precision voltmeter of the 1% accuracy type connected across the meter terminals. An
indication on the test meter will show that the panel meter is open. Check the wiring for an open circuit, or
replace meter if circuit wiring is complete.
2. A shorted voltmeter will show no indication. Battery current through a shorted meter will cause a
visible indication such as smoke from burning wire insulation. Disconnect the charger from the battery and
AC source and replace the meter and damaged wiring.
3. If the meter calibration is in doubt, checking against a precision meter will determine if the panel
voltmeter is off calibration more than two percent.