[Premium-Rx] Collins 651S-1 advice sought

[w3jn at verizon.net]

Nick, as you observe, troubleshooting these is pretty difficult without the extender cards - but it can be done and tacking test wires to the board is about the only way to do it.
You may need both the DCU and DCFE cards, or at least one of them, because as I recall one of them replaces a board having a bunch of diodes and a few ICs that routes control lines around to account for different options, such as the VLF front end, filter daughterboard, squelch, ISB, etc.
The boards should have those plastic levers on each edge, with the board nomenclature to aid in removal.  Card cage may have gotten a bit bent, not sure if you can loosen the front and back edges a bit so the cards slip in and out a bit easier.  I have not seen that problem (hard to extract cards) with any of those I've worked on.
Your first step, since it has DCU and DCFE boards but the version number does not indicate remote control, is to go thru that big version table and verify you have the right version of *each* board for the radio.  Many of the cards have subtle differences to account for options.  This might be the issue with not tuning above 9.999 MHz.
I have a bunch of 651S-1 boards, mostly unknown condition, but I can check them out IF the versions correspond to my 651S-1s and yours, and they're the right versions.  I also have a NOS S-meter, but yes there is a small light behind it and as I recall it's not all that easy to change (but neither is the meter!)
Finally, the mod to disable the tuning mute is simple, there's a mute diode on the power supply board that you can lift one end, or cut the mute line trace.  It's strange that Collins routed the audio mute thru the PS board.
Good luck, it's really a fantastic receiver, and I like it much better than my 51S-1.  It has outstanding audio, and just looks/feels "right".
73 John


-----Original Message-----
From: Nick England <navy.radio at gmail.com>
To: Premium-Rx at mailman.qth.net <Premium-Rx at mailman.qth.net>
Sent: Mon, May 27, 2019 8:28 pm
Subject: [Premium-Rx] Collins 651S-1 advice sought

In a fit of Xenia/Dayton sunstroke madness, I bought a 651S-1 receiver
(Collins p/n 522-4836-152). Having heard about this receiver for years, I
figured it would be interesting to have one and the price wasn't too
outlandish.
http://www.virhistory.com/ham/dayton-19/IMG_2584.JPG

The seller said it worked and it does, mostly.
Major issue so far - The 10's of MHz is stuck at 0 so it is fine up to 9.9999
MHz. Both display and synth are stuck so the problem must be in the upper
2-bit counter circuit on the A14 board and I can probably figure that
out with some scoping. I don't have an extender card, so I'll have to
remove card, tack on a few wires, reinsert card, scope a bit, repeat as
necessary.
So - the questions -
1) What is the trick to pulling these cards out? I finally used a vise-grip at
the corners of the A14 Freq Ctl Ckt Board, but I don't want to keep doing
that and munge up the card.
2) What to my wondering eyes should appear but early flat-pack TTL and
DTL logic.
Is there any source for this stuff nowadays?
3) Is there any reason to keep the DCU and DCFE boards? I'm not going to ever
try remote control and IF I get lucky, I might be able to rob a chip I need
off them.
Can I just pull these cards out or are there jumpers I need to fix? This is a
-152 version receiver which the manuals say comes without DCU/DCFE
4) Does anyone have a junker A14 board? Want to trade for DCU/DCFE?
5) Does anyone have a spare cabinet? This is rack-mount unit with speaker, but
no cabinet.
6) The meter is working but not lit - I assume there is a lamp inside there
somewhere.
7) The USB signal is weak but working - so that's another board to scope
out.

All in all, it was a reasonable gamble and I think I'll have a good experience
using it. The audio muting when changing frequency is odd, but I recall
seeing a hint about defeating that. The fluorescent displays all work, but
are dim. I may do the LED conversion some day but that's a future project.

Cheers
Nick
-- 
Nick England K4NYW
www.navy-radio.com
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