[time-nuts] Basic HP 5334A question

[Rick Karlquist]

Bob Camp wrote:
> Hi
>
> Other than the normal issues with blown inputs, the 5334 is a pretty
> rugged
> beast. It's not got a whole lot of crazy stuff inside it. It does have
> some
> custom IC's and firmware.

Actually, it has crazy stuff IMHO.  The controller is broken up
into three separate microprocessors because of various historical
accidents.  The custom IC's are somewhat "crazy" as well in that
the circuits could have been replaced with OTS IC's, which is
what I did in the 5334B.  I unfortunately inherited the 3 uP's
and couldn't design them out.  The power supply in the 5334A was also
weird in that the oven warmup current would pull it way down in
voltage, below its spec.  The counter accidentally worked anyway,
but if you were troubleshooting, you might think it was broken.
The PC board had a weird single point ground, instead of a ground
plane as in the 5334B.

Rick Karlquist N6RK
Project Manager HP 5334B, circa 1987