There is no GBIP on this unit.
It turns out the -30v is dead. After replacing VR605 (7924 voltage regulator), the multimeter boot up 'properly'.
Now I facing a few other issues.
There seems to be more power related issue. If I plug back the AC RMS module plugin, the display flickering.
Then I found out the 2 input relays (K301, K401) are gone ... Here I stuck with another problem.
The multimeter boot up but stuck with all lights on. If I touch any button, it get to '0' (standby?).
All button seems to do the right thing, changing mode, changing samping rate etc ...
But the sampling rate light (S, M or F) stay steady, not blinking at the rate of sampling.
Does it means there is no sampling signal?
I connect the front lead to voltage source and nothing change. The display still show '0'.
I replace K301 and K401 with a normal mini 5V relay but nothing change.
Now I need to trace the circuit to see how the sampling circuit works ...
Any advice will be welcome.