[volt-nuts] HP 3456A -3 Fault

[David Smith]

Hello Friends,
I have two HP 3456A's that have the same "-3" fault in the "test" mode. Both DVM's started exhibiting this same fault about the same time. I've troubleshot one of the DVM's to a failure in the Isolation Logic "Transmitter." I have no waveform at the output of A3T1.
Before I continue with troubleshooting I thought I'd ask a question of the group.  Is there a common mode failure of these DVM? Is there something in particular or area that I should be looking at/for?
It's probably coincidental that they would both fail at about the same time with the same -3 fault.
Your input is greatly appreciated.
Best regards,

Dave - W6TE