[GreenKeys] Navy CV-3510A Converter Repair/Recap

[Jeff G]

I brought home one pair of TTY converters from the ship to go through and
possibly recap. I was told that at least one out of this pair "smoked" at
some point. The bottom one of the pair turned out to actually be working.
The top one seems to be pretty goofed up, so I figured I'd post up here
incase anyone actually has some former experience working on these things
and could offer any advice.

Caps - out of the 10 or so electrolytics, the 3 large primary caps kinda
read OK and leakgage was ok-ish (for 40yr old caps), and maybe 1-2 others,
but all the rest were absolutely failed/bad. Cap reader was seeing
picofarads instead of microfarads. Upon pulling them, I'm seeing actual
crisp/burn marks on the bottoms of them. Wondering if this thing saw a
surge or maybe got hit with lightning at some point, of if maybe that was
normal for these guys. All the caps appear original/made-in-USA and the
bottoms have a red gooey blob. (Only one cap showed actual physical
leakage).

Interestingly, replacing the primary caps which are axial I thought would
be a pain, actually went great/quick - there's a smaller cap sistered in
between each one, and I found using the foil hole for the smaller cap
worked perfect to mount a radial cap in place of the axials. Then for the
smaller cap, one half goes in the hole, the other side I just cut short and
solder to the leg of the larger cap that goes to the foil.

This thing is still having some interesting problems though; the
synthesizer board seems to be working OK - the primary clock generator is
dead-on accurate and stable, and seems up to the demodulator board
everything is good. The demod board is a mess, mostly around the bandpass
filters. It actually works...mostly...but for example, if I feed a solid
1575hz mark signal to it from a signal gen, it'll be good for maybe a
minute or two, and then "fade" out. 1-2 mins later, fades back in again.
When its good, it decodes and prints, but then out of the blue, it fades
and just stops printing for 1-2 mins, and starts printing again.I think
it's adjustments, but the manual is fairly hard to follow in this regard.
The patterns on the CRT look like a trippy 1960s disco video vs what I
expect.

Also the CRT is very dim; heater voltage looks OK, and I have the
brightness as high as it'll go. Unfortunately my o-scope at home can only
do 5v/segment, so with a 10x probe, can only read up to 400v (50v x 8
segments). The manual calls for reading 630V that I just can't do.
Ironically, I found a 3" version of the tube in my piles, so I may plug
that in to see if its any brighter to prove whether its the tube or the
unit.

Has anyone ever repaired one of these?

[image: Photo Mar 01 2023, 12 14 15 AM.jpg]
[image: Photo Mar 05 2023, 8 56 26 PM.jpg]
[image: Photo Mar 05 2023, 10 20 58 PM.jpg]


Jeff
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