Stick to Your Own Rules!

If you have Carver repair questions, or can help other users with repairs, this is the place for it
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Robert R
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Stick to Your Own Rules!

Post by Robert R » Fri Aug 15, 2014 12:01 pm

One thing I always advise guys is to repair a non-working unit first, before recapping it. Even if recapping is the obvious next step, don't just do it, hoping the problem is a bad cap or two, and that after recapping all will be well.

It had better be, because if it isn't, you are in a world of trouble. You now can't tell whether there were non-cap problems going in, or if you installed one backwards, or left a solder bridge someplace, or pulled something loose with all the handling. All those things can happen, easily.

When I went to Taiwan late last November, I took my little HR-722 receiver along. Actually, it's not so little, as it adds 35 pounds to a suitcase, but I didn't want to spend three months without any Carver gear. Thought Id leave it over there, to have on future trips.

Any such plans became moot when it arrived DOA. Wouldn't lock the on relay – just a click, then off again. No dents on it, but it won't work. Kaputski.

So I pulled her apart, and first checked the Standby board – it's small, and that's where the on relay is, so it seemed a good place to start. I checked it out pretty thoroughly – everything OK there, so I moved on. But before screwing the litte board back in place, I replaced the couple of small electrolytics on it. After all, I'd planned to recap the whole unit during my stay, so why not get a start?
Big mistake.

Found the problem, on a board that's sandwiched between the tuner and the main amp boards. It's called the Hologram board, but half of it has nothing to do with SH; it just provides space for lot of the power supply parts – maybe half a dozen regulated supplies that send power seemingly everywhere. Anyhow, it had been repaired before, it seems, and one of the foils was patched with a little piece of solid wire, probably a bit of a clipping from a resistor or something. The whole Mickey Mouse deal had busted loose, so I fixed it – bypassed the whole thing with a nice piece of red stranded wire, and glued it down. Checked all around with a nice cheap ohmeter I bought up at the electronics district. Everything looked good, and I hadn't wrecked any of the cheap connectors that feed flat ribbons of wire everywhere, board to board. Those junky things don't like to be handled.

Fired her up, but it still had the same problem, or at least the same symptoms. So now what? I'm 8000 miles from home, with a few lousy tools and a cheap VOM, with all the writing in Chinese. Jumpered the relay to make her run, and it seemed to want to, but some resistors at the power transformer started to smoke before I could even start taking voltage readings. Tried re-wiring it for 240 volt use, figuring that at 120, the standard voltage there, it would be low enough to work on. Wrong – it still smoked at half voltage. Had to give up. My friend there said to throw it away – he's definitely not an OCCD sufferer. I carried it home.

Finally got around to it the other day, about nine months later. Cleared my workbench off and took a shot at it. First session involved just getting my head back into the problem, remembering where I left off in November.

It was wonderful having the paper Service Manual, instead of trying to find my way from board to board with different, sideways pages on a laptop. You can't pencil in little notes on a computer screen, but my manual, used many times before (it also covers the nearly identical 752 model), has nice little notes showing where each board interconnection goes, among other improvements.

So I jumpered the relay again and fed in just 25 volts, and now no smoke, and everything seems OK, but it still won't latch on. The tuners act weird, too. Something is telling the latching circuit to not latch – it could be most anywhere, and receivers are pretty complex. After a frustrating couple of hours I realized I'm just repeating myself. Time for a brain-reboot, so I quit.

Next session I looked at things afresh, and went back to the place I started – the little standby board, where the “on”relay is. Every part seemed to test OK, but I found a circuit foil busted, right where I had installed a new cap! Fixed that, and on she came, though now the tuners wouldn't switch right.

Still cussing myself out, I rewired the tuner board connections – those shitty plugs had failed, due to the excessive handling I should have never given them, after breaking my own rule.

And that did it – all working again, finally.

Today's poem

Between the time I fucked up and now
I could have had a baby, if I only knew how
.


RR
"You know what folks? I'm happy."

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TNRabbit
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Re: Stick to Your Own Rules!

Post by TNRabbit » Wed Dec 17, 2014 7:22 am

Thanks for sharing, Robert!
TNRabbit
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Magnaryder
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Re: Stick to Your Own Rules!

Post by Magnaryder » Wed Dec 17, 2014 8:19 am

Thanks Robert, very enlightening.

ray
Magnaryder

Its going to be used equipment when I sell it, so it may as well be used equipment when I buy it.

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Robert R
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Re: Stick to Your Own Rules!

Post by Robert R » Wed Dec 17, 2014 12:19 pm

Thanks guys. I'd like to think that the reason nobody commented for 2 months was that the piece was so well expressed that there was nothing more to say, but sometimes I thought maybe they just wanted to be kind and not agree that I'd acted like a doofus...

RR
"You know what folks? I'm happy."

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kingman
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Re: Stick to Your Own Rules!

Post by kingman » Wed Dec 17, 2014 12:30 pm

I was so awe struck I couldn't type!
In reality, it only matters what it sounds like to YOU!!!

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fill35U
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Re: Stick to Your Own Rules!

Post by fill35U » Wed Dec 17, 2014 12:51 pm

I actually read when you first posted this, very inspiring!

But of course, Murphy's Law will make it so the last step of your troubleshooting narrows it down to the cap you *didn't* replace! ](*,)

Recapping is also a more methodical process that builds familiarity with the gear. You might notice trouble spots along the way that could help you troubleshoot later.

And yes, it was so well written that there's not much to add! :)
Living room system: TGP IV, TX-8r, TD-1400, PT-2400(x6), PM-1.5a(x3), TFM-45(x2), TFM-55, Silver Amazings Mk IV

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pmat
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Re: Stick to Your Own Rules!

Post by pmat » Wed Dec 17, 2014 12:54 pm

I hope you didn't use aluminum! :-#
Power is the aphrodisiac of audio

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Robert R
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Re: Stick to Your Own Rules!

Post by Robert R » Wed Dec 17, 2014 1:28 pm

Actually, all those electrolytic caps are aluminum. Never thought about that before...

RR
"You know what folks? I'm happy."

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