Garey Barrell <[EMAIL PROTECTED]> made an utterance to the drakelist gang
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Craig -
Unfortunately, neither of these ICs are socketed. (Unless it's one I've
repaired!) Generally, I'm against sockets for semiconductors, since
they're almost always less reliable than the semi. But the 4016 is one
I'll make an exception for. Be sure and use a GOOD socket. There are a
lot of junky ones out there, and considering what is involved in getting
to these, a dollar or two for a good socket is money well spent.
The 4016's are temp sensitive in this failure mode, and so can be
intermittent. A little shot from a heat gun or freeze spray, or even a
nearby soldering iron can be used to encourage them to present. Failure
usually presents as a stable voltage on the input side, and a jittery or
drifting voltage on the output.
The 5.645 crystal "BFO" (Carrier oscillator) is trimmed by the sidetone
adjust, and corrosion on this trimmer "could" also act like what you are
seeing. All four signals are accessible on the parent board, 40 MHz,
13.695 MHz, 8.05 MHz and 5.645 MHz.
Adjustment / alignment procedures are shown in the Service Manual.
73, Garey - K4OAH
Atlanta
Drake C-Line Service Manual
<http://www.k4oah.com>
Craig Roberts wrote:
Thanks very much for the circuit description, Garey. The "frequency
sweep" appears to affect BOTH the sidetone and transmitted signal --
which is why I wondered how CW is generated in this rig. Curiously,
the problem disappeared shortly after I wrote the messages last night
and failed to reappear this morning. So, it's intermittent -- the
bane of technicians. Your mention of U1001 is most interesting since
mode switching and passband tuning activation triggered the problem
(but not this morning :-) ). If this device is socketed, I could have
a simple contact problem, I suppose. I'll check it out tonight.
I'm open to other ideas, too.
Many thanks!!
Craig
W3CRR
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