Fluke 8842A multimeter stuck in remote mode

[raymond008]

Hi,
I recently got a fluke 8842A bench top multimeter.
Somehow, it get stuck in 'Remote' mode with no other digital display.
Does it means it failed to power up reset or it is actually locked to 'Remote' operation only?
Any hint?
Thanks.

[J-R]

Does the unit have a GPIB interface installed?  You could try removing it as a test.
Local button does nothing?
What happens if you try the full self-test?

[raymond008]

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.

[raymond008]

How do I trigger a full self-test?

[J-R]

Start reading at section 6-36 of the manual.  There is a ton of good troubleshooting information.

https://dam-assets.fluke.com/s3fs-public/8842a___imeng0300.pdf

[raymond008]

Thanks for the pointer. Looks like chapter 6 is a good starting point.
It mentioned about power supply multiple times.
I went back and check all supplies. 2 of them still out of spec.
7.5v mesasured as 4.2, -8.2v measured as -3.2. Definitely not right.
However, it's not zero. So, it's not a short on filter cap. I desoldered
CR613 and CR614 zener for that 2 voltages, they measured fine.
Now need to trace to the sink side to see what load them down.
One of them connect to the fluke custom analog switch. Need to find the pin out of them ...

[raymond008]

I push SQR button to start self-test.
It stuck at 06 ...