Exide Technologies Section 93.30 - Manual (Page 13)

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4. Check square wave pattern at test points A1, A2 and A3. Note the 120-degree (5.5 mS) delay between the
three patterns (scope synchronized to the 60 Hz AC line). If A1 pattern is missing, replace IC3. If A2 or A3 is
missing, replace IC4.
5. Check ramp pattern at B1, B2 and B3. Compare with those shown in FIGURE 2. Note that the exact wave
shape depends on the phase angle of SCR gates. The steeper the ramp the earlier in each half cycle the SCR is fired
and the higher the output of the charger. If waveform at B1 or B2 is abnormal or missing replace IC2. If B3 waveform
is missing replace IC1.
6. Check waveform at test points C1, C2 and C3. This comparator pulse generator produces rectangular
waveforms of varying lengths with the leading edge varying in position to a fixed-in-time trailing edge. Compare with
FIGURE 2. If C1 or C2 is missing, replace IC2. If C3 is missing, replace IC1.
7. Check waveform at test point H. This waveform should be a continuous string of very short pulses with
approximately 10V amplitude. This is the picket fence generator output. If missing, replace IC3, IC5 or IC6.
8. Check bursts of picket fence signal at test points D1, D2 and E3. Compare with FIGURE 2. If D1 or D3 is
missing, replace IC4. If D2 is missing, replace IC3.
9. Check amplified picket fence pulse trains at test points E1, E2 and E3. These pulse trains are similar to
those at D1, D2 and D3 of FIGURE 2. If E1 is missing replace Q1 or Q2. If E2 is missing, replace Q3 or Q4. If E3 is
missing, replace Q5 or Q6.
Note: The following check should be made only after completing steps 1 through 9 above. Chargers with
output ratings higher than 150 Adc may be supplied with an Auxiliary Gate Drive PC Board (A14)
triggering the phase-controlled SCRs. The A14 board intercepts the SCR gate lead wiring from the
control module (A1) as shown in drawing EH0617 on page 31. The A14 board converts the “picket
fence” pulse train (waveform similar to D1) from the control module to a DC gating signal for the main
SCRs. The A14 output will be a square wave approximately 1.5 Vdc in amplitude.
10. If a main SCR fails to turn on, trace the gate signal from the control module to A14, and from A14 to the
appropriate SCR. The AC gate signal should be approximately the same magnitude at both input and output of A14. If
an input gate signal has no corresponding output signal, replace A14.
11. If a main SCR fails to turn off, resulting in a high charger output voltage, disconnect SO14 plug from A14
board. If the main SCR now turns off, replace A14. If the main SCR remains on, the main SCR is defective and must
be replaced.
12. Check ripple waveform symmetry of the charger by connecting the oscilloscope ahead of the filter choke
(L1). Connection may be made across the bleeder resistor (R1). With the unit adjusted for about 66% output current,
observe to determine that the 360 Hz ripple pulses are of uniform amplitude. If not, slowly adjust the two balance
adjust potentiometers (R24 & R32) on the trigger board (A1). Note that phase #1 is not adjustable and is used as a
reference. Adjust the two potentiometers for the most uniform pattern yielding the lowest ripple voltage at the output
terminals. This adjustment may also be made using a sensitive AC voltmeter at the charger output terminals, and
adjusting for minimum RMS voltage indication (less than 30 mV for a filtered charger).
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.