[Test-Equipment] HP 34401A DMM display problem

[cmos at shol.com]

Dave,

I have fixed several of these meters.
If I remember correctly, about the only
other things on this board is a custom 
chip on the back. I do believe this display
board is still available from Agilent, and 
I think the cost was about $90.

There are about 3 different revisions of the
main board over the years(only the first version
is shown in the manual), but I think all the 
display boards are compatible. 

Jim, 



------- Original Message -------
>From    : DaveC[mailto:davec2468 at aim.com]
Sent    : 11/7/2010 1:47:08 AM
To      : test-equipment at mailman.qth.net
Cc      : 
Subject : RE: [Test-Equipment] HP 34401A DMM display
problem

 Bought recently, tagged as "needs new display". When
I first powered 
on this unit the display worked. After pressing a few
function 
buttons, display went dark.

Now when powered on the display goes all-segments-on
and stays like that.

I swapped in a known-good display and the DMM works
as expected: no errors.

Anyone have any experience with the display PCB on
this or other 
unit? The fluorescent matrix clearly works; it's
something to do with 
the on-board support circuitry.

Thanks,
Dave
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