[time-nuts] Faulty HP 10544B
Denis Dowling
dpd at opsol.com.au
Sun Mar 26 22:56:21 UTC 2023
Hi All,
This is my first time on the list so apologies if I am going over an old
topic.
I am repairing a HP 8662A Synthesised Signal Generator that I purchased
from a government auction. The unit was purchased without any
information about its working state and I have fixing various issues
with it. Firstly there was a digital logic problem with the keyboard
card that was causing the generator to periodically lock up. When this
was fixed the unit came to life but the output signal level was down 5dB
and this was traced to a bad step attenuator. I attempted a fix but
ended up needing to replace this to get the output steps correct.
I have now turned my attention to calibrating the reference timebase and
unfortunately this seems to be well out of spec.
The timebase is a HP 10544B 10MHz OCXO. The 10MHz output of the
oscillator seems to be ~40Hz low. I have attempted to adjust the unit
via the multi-turn capacitor adjustment but this seems to be at the end
stop and the frequency is still low. So my questions are:
1) I assume this module is faulty as it is so far out of spec? The
signal generator has been powered off for multiple months but even after
having the unit powered on for 6 hours the frequency has not changed
significantly.
2) How repairable are these modules? I ended up blowing $200 on the
replacement step attenuator so will need to save up for any new parts. I
can always use an external 10MHz reference but it is always nice to have
equipment complete.
3) From searching the list it seems that the oven could be what is
faulty. Would a cold over account for this much error? If so I will pull
the module and check this.
4) Finally is the OCXO just worn out and has aged beyond the point it
can be adjusted back into spec?
Regards,
Denis
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