2. Service
Functional-Group-Diagnostic Trees (Diagnostic Section 2)
70
2.1.2.3.0 A1 Fault
1 Remove power, ensure interconnecting cables are not shorted, then either
troubleshoot or replace A1, and retest.
The problem is on the motherboard (A1), in one or more of the following:
CR3 full-wave bridge rectifier circuit,
C4 and R4 filter capacitor and bleeder resistor , or
Over voltage protection circuitry (around CR1).
You may elect to use the A1 Theory of Operation information in chapter 3 to
effect component-level repair
2.1.2.4.0 AC-Line Fuse Fault Isolation: A11/A12 Inputs
If the ac-line fuse doesn't blow after disconnecting A11P101, then the fault
can be further isolated:
1 Reconnect all connectors. (Install a new fuse if necessary.)
2 Disconnect A1P2 from A1J2 on A1 motherboard. (This breaks the circuit at
the dc-dc power converter module, A12.)
3 Apply ac-line voltage again.
4 Check the ac-line fuse immediately for possible open condition.
QUESTION: Did the ac-line fuse blow?
If Yes: Go to, 2.1.2.5.0.
If No: Go to, 2.1.3.0.0 (Fault is in the A12 power supply module or
the circuits loading the supply.
2.1.2.5.0 A11P101 Connection Test
1 Disconnect A11P101.
2 Check for a short circuit between pins 1 or 4 (positive side) and pin 2 (gnd) of
the cable using an ohmmeter or equivalent.
3 Verify that the pins are not shorted: flex the cable several times to ensure
there are no intermittent connections
QUESTION: Is the cable faulty?
If Yes: Replace A11P101 cable, and retest: go to 2.1.1.1.0.
If No: Remove power, replace A11, and retest.
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