I did an on-site inspection and I couldn't find any strangeness.
But MCF couldn't be recovered yet though I tried to reboot, cold-boot, etc.
I thought replacing HIB card is a thing we should do at first.
Remaining works can be done in parallel with IFO works because it's now related to the power sources and IMC SAFE is not required.

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Check log
- DC24V is served properly from the power source according to a check by multimeter
- DC3V, 5V, and 12V are properly provided on the mother board according to a check by multimeter.
- Timing Slave seems to be synchronized according to an indicator on the front panels of Timing Slave and Fanout.
- ADC and DAC seems to be launched according to an indicator on each board.
- HIB card also seems to have no problem according to an indicator on the board.

Concerns
All AI output cables were not screwed and a GND pin side of some of them were half unplugged. I'm not sure it's a cause of this problem. But such kind of usages can make troubles on electronics. Note that "Portable" is not a reason of allowing unfixed cables. Before I started my work, I screwed all cables on the AI output. Please ensure that cables are screwed on the front/rear panels.

The speaker seems to emit a popping sound when IO chassis is ON/OFF. (I haven't check a situation when AI chassis is ON/OFF. And also, it may emit when the real-time models are launched up properly though they cannot be launched now.) Anyway, I thought my heart stop beating. It might be better to stop the speaker amp by corresponding persons before starting maintenance works or to share for maintainers the procedure to stop/re-start the speaker amp.