Hi Randy,
Thanks for the post, but I had already seen that video. Nothing new there
that I didn't already know.
I used to have an older 887AB that had the mechanical chopper. I installed
the chopper-stabilized opamp circuit that you developed and posted; it
worked great in the unit. I traded it for the unit that I have now (didn't
work at the time I traded, but the repair was easy - had a bad transistor in
the +18V power supply regulator). The unit I have now is a much better
instrument - less needle jitter, better long term stability.
I've always been paranoid about having service documentation for all my
equipment. Never know when it will be needed, and could be the difference
between a good repair and having to junk an otherwise good piece of gear.
Surely, Fluke must have supplied the correct manual with this instrument
when it was sold. Maybe someone, somewhere, sometime will see this post and
happen to have a good schematic for this unit.
Thanks again,
DaveM
Randy Evans wrote:
No manual but here is a youtube video on the unit.
https://www.youtube.com/watch?v=EQRg8Ot5WDM
On Wed, Feb 27, 2019 at 6:54 PM Dave M <[email protected]>
wrote:
I have an 887AB (s/n 2513) that I acquired a few months ago that has
a new Null Detector board that I'm curious about.
The board is a (factory installed) null detector board that uses a
single opamp, a Burr-Brown OPA-111.
I bought a manual for this instrument from Artek Manuals that covers
the serial number of my instrument, but there's nothing in the
manual about the
new null detector board (887A-4022, p/n 812610). If anyone has any
information (a schematic would be wonderful), I'd love to get a copy.
Thanks for any help
Dave M
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