Circuit for HP3421A Data aquisition

It may sound incredible but we are still using HP 85's and HP 3421A's in our workplace. Slowly, the HP3421A's are dying, and to get them up and running again I dearly need a technical service manual or the circuit diagram of the motherboard. Can anybody help?


Hello Barrie,

Good to see you are still using the HP3421A's.
I do to, however mostly as MUX infront of a HP34401.
But sometimes I bring out the old Thermo Couples. I still need
to build a connection box for K-couples.



You've got mail.




Thanks for your responses guys. Now the drama starts while I try to nut out what all these error codes are really trying to tell me. Cheers


Hi Barrie,

The error codes you can find in the Operating manual on page 18.
On one of the HP3421A's I get an Error 0.
Most likely due to moving the 44462A Units.
On the other one a 19... it took me a while to realize that that one
is under HPIB control, so that's the HPIB address.



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