2-3
WARNING: DISCONNECT POWER PRIOR TO SERVICING
2. Disconnect connectors P1, P2, and P3 on the circuit board assembly.
3. Loosen the power supply circuit board mounting hardware.
4. Lift the circuit board from the mounting pins and remove the circuit board from
the cabinet.
2-17.
TROUBLESHOOTING PROCEDURES.
The power supply module troubleshooting
procedures are presented in Table 2-1. During the execution of the troubleshooting
information, perform all the procedures for a symptom. The symptom may contain
multiple component failures. Once the trouble is isolated, refer to the circuit board
theory of operation and schematic diagrams to assist in problem resolution.
TABLE 2-1. POWER SUPPLY MODULE TROUBLESHOOTING
(Sheet 1 of 2)
SYMPTOM
CIRCUITRY TO CHECK
1. RED POWER SUPPLY
1. Check for an over-temperature condition by
INDICATION
inspecting the fans and filter.
2.. Check transistors Q21 and Q22 as follows:
A. Using a digital voltmeter, operate the voltmeter
to diode check. On Q21, place the negative lead on
the drain (center pin) and the positive lead on the
source.
1. If the voltmeter indicates a non-shorted
condition, check transistor Q23.
2. If the voltmeter indicates a shorted condition,
proceed as follows:
a. On Q21, place the negative lead on the drain
(center pin) and the positive lead on the gate
and record the voltmeter indication.
b. On Q22, place the negative lead on the drain
and the positive lead on the gate and
record the voltmeter indication.
c. The transistor with the lowest voltage is
defective.
2. Place the negative lead on the drain of Q21
and the positive lead on the source and
determine if a short circuit condition is
present.
3. If a short circuit condition is present,
defective Q21.
B. Repeat the procedure for transistor Q22.
3. Check transistor Q23 as follows:
A. Using a digital voltmeter, operate the
voltmeter to diode check and troubleshoot
transistor Q23 as follows:
1. Place the negative lead on the drain
and the positive lead on the gate and
determine if a short circuit condition is
present.
