[time-nuts] Synthesizer Unit (A1) For An HP 8061B

w3kl at w3kl.com w3kl at w3kl.com
Mon Jan 5 10:23:04 EST 2009

You may recall that I posted a series of questions several months ago regarding my HP 8061B.
In summary, I was finding that the system would appear to lock but the continuous operation LED would not come on.
Several people who frequent this board offered some very good suggestions.  Over the holiday, I immersed myself in the problem and have finally narrowed down the part of the system that isn't operaing:
I am finding that, based on the manual, the synthesizer is locking but the circuit used to report a synthesizer lock to the logic board is not behaving properly.
I don't have the schematic in front of me, but the circuit involves Q23 (a JFET) used to amplify the error signal in the loop followed by Q24, Q25, and Q27 (all NPNs).  If the system locks, Q27 (emitter follower) is supposed to go "low" (<1.5 V) but in my case, despite the fact that the input to Q23 appears to be DC (indicating a lock), Q27 is actually at 6V.
I have not dived into diagnosing the problem in detail (will try to get to it this weekend).
However, has anyone else seen this problem?  If so, what did you do to resolve?
Finally, does anyone have a spare A1 board for an 8061B that they would be willing to sell me?

Jeffrey K. Okamitsu, PhD, MBA

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