HP 8640B - OPT 323 Service Manual

[SuperMario]

Hi,
I am looking for the service manual for HP 8640B - OPT 323. This is a military version of HP8640B. The problem is in the frequency counter circuit, it displays 60% of set value. RF output is at correct frequency. I have manual for the 8640B but counter part is different. If anyone can help with this issue please let me know.
Thanks.

[sbrom]

Hi,
I am looking for the service manual for HP 8640B - OPT 323. This is a military version of HP8640B. The problem is in the frequency counter circuit, it displays 60% of set value. RF output is at correct frequency. I have manual for the 8640B but counter part is different. If anyone can help with this issue please let me know.
Thanks.

Don’t know if this is real, but here’s a manual listed for sale, $65.  I’ve not seen a free pdf with the option 323.

https://fairradio.com/?s=Usm-323

[alm]

It might be worth emailing Dave at Artek Manuals to see if any of the 7 different scans he sells cover option 323. Not free, but not $65 either. The 8640B-AN/USM-323 manual sounds like it might be the right one.

[joeqsmith]

https://antiqueradios.com/forums/viewtopic.php?f=8&t=252760

[SuperMario]

Ordered one from ArtekManuals for $12.50. Still waiting for download link.
Thanks for the suggestion.

[LazyJack]

They usually send the link in a day or two. It seems to be a somewhat manual process. They are very helpful and responsive, should there be any problem.
It is well worth the waiting, they are very high quality scans.

[SuperMario]

Got my manual and fixed the unit. Thanks everyone for the suggestions.

[Dave Wise]

Yay!  So what was wrong?

[SuperMario]

My apologies, completely forgot about this response.
The problem was in the counter circuit U9. This divider ic was dividing clock signal incorrectly. Replacing this IC restored correct functionality.