Tadiran Telecom SMVH09A-2A1B1NA Service Manual page 45

Troubleshooting
(4) Malfunction of Zero-crossing Inspection Circuit Malfunction of the IDU Fan Motor L1
Main detection points:
● Instant energization afte de-energization while the capacitor discharges slowly?
● The zero-cross detectioncircuit of the main board is defined abnormal.
Malfunction diagnosis process:
42
Start
Turn power off for
1minute,the turn
back on
U8 is still
displayed
Yes
The zero-cross detection circuit
abnormal.Replace the mainboard
with the same model
End
The unit returns to normal.
No
Conclusion:U8 is displayed due to
power off/on while the
capacitor discharges slowly.