Fluke-85 VDC error

[halexa]

Latest status,

I desolder all caps surrounding Z1 so I could access all traces around Z1, and gave the PCB a new IPA bath with a good scrub partially around Z1 and U4. I examined the PCB under microscope to see if there was anything interfering with the pins of U4 or the traces around it and followed all traces to and from Z1. And everything looks good.

But the status of the 85 in the VDC mode  is still broken.

So as a desperate action i desolder the U4 to see if there was something under the IC that I was missing, but that did not help either.

Was next a new CPU? or a new meter?



 

[ModemHead]

I'm impressed with your determination!  Sounds like you've eliminated the possibilities for a simple repair.  I'm sorry I can't think of any other ideas now, if the input to the ADC is wrong, the meter is going to read wrong, simple as that.

Was next a new CPU? or a new meter?

This model is too old to find a new CPU. There's the possibility of finding a parts donor, which according to the parts list, can come from an 85 or an 83.

[halexa]

Thank you all for superb guidance in my attempt to fix my Fluke85.

Guess its time to start scanning the auction sites for an 83 or 85 with a smashed LCD.

[retiredcaps]

I have bought an used Fluke 85 DMM.

Just curious if this 85 you bought was advertised as working or for parts only?

[halexa]

It was advertised as " powers up but unknown functionality" so it was a gamble from my side. Only paid 30usd for it.

[retiredcaps]

Only paid 30usd for it.

You can easily recoup that money by selling the Fluke 85 parted out.  The holster, fuses (if they were good), front/back case, zebra strips, lcd, input jacks all sold separately could net around $60 to $100.