[Test-Equipment] HP 8640B Counter Not Working Properly

[Darrell W4CX]

Hi Barry...are you still working on your 8640?  I had one for several years
and had two problems with the counter, although I never had a symptom of all
zeros.  Usually there was a decade off, or other weirdness.  I had to find
some unobtanium 74xx ICs to get it fixed.  

I do have some material (manuals, etc).  Would you like to have them?

73, Darrell W4CX

(HP 1974-2007)

-----Original Message-----
From: Test-Equipment [mailto:test-equipment-bounces at mailman.qth.net] On
Behalf Of Barry
Sent: Monday, February 09, 2015 12:47 PM
To: Test Equipment
Subject: [Test-Equipment] HP 8640B Counter Not Working Properly

The counter on my generator shows all zeros (both in INTernal mode and
EXTernal mode when connected via the front panel BNC jack).  I fed the
external time-base (rear BNC jack) to a counter and verified 5Mhz is present
there.

My first step will be to verify that a signal is indeed making it to the
counter board.  If that is present (and I assume it probably is), then I'll
have to investigate the counter board(s).

Is it a valid method to trace out the signal path with a scope?  In other
words, I think I should be able to verify there are ECL-level and/or
TTL-level signals along the path and at least be able to see if there's a
point where the signal stops.  At that point, then I would start looking for
bad components, etc.

Is that a viable approach?  I assume that tracing this out with a scope
probe won't give me false readings due to loading, etc.  Is that correct?

Thanks,
Barry - N4BUQ
______________________________________________________________
Test-Equipment mailing list
Home: http://mailman.qth.net/mailman/listinfo/test-equipment
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Test-Equipment at mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html