Tried to recap a tube receiver, and failed.

I tried to re-cap a tube receiver (amplifier + tuner), and now when I turn it on it starts playing music for a few seconds after it warms up, then the music fades out and and hum takes over. I don't really know what I'm doing, and the wiring inside looks like a mess of spaghetti. I'm pretty sure I replaced the caps properly, but I used .068uf WIMA caps to replace .050uf wax/paper caps, and I'm wondering if the value difference, added up over 8 caps would make a difference? Other than that, does anyone have any advice based on my description of the unit's behavior? Any comments whatsoever might be helpful..

Reply to
Derwin
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Don't mean to be harsh but find someone who knows what they are doing.

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Reply to
Meat Plow

Try news:rec.antiques.radio+phono That is why the group was created.

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Reply to
Michael A. Terrell

No.

At this point you need to fault find. Does it work OK with tape or other music input?

Reply to
Homer J Simpson

I wouldn't delve that far, sounds like a PS/PA problem. The OP is confused man, he said it looks like spaghetti.

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Reply to
Meat Plow

Wow, I was expecting a higher calibre of responses. I'll look into that rec.antiques.radio+phono group...

What exactly do you have against spaghetti, anyway? Is it a racist thing about italians, or?

Reply to
Derwin

That's not what I've read. Are you sure you're not thinking of electrolytics?

Perhaps I should have specified that the unit worked fine before I recapped it. It had a bit of a squishy sound so I figured it could use a re-capping but I must've screwed up somehow. But re-capping is pretty straight-forward, and I think I did it right. So now, what could have gone wrong? Switching inputs is not going to help me track down the problem at all. C'mon, I may be a 'self-taught' novice electronics tinkerer, but that is downright stupid - I already said the music plays fine for a few seconds after it warms up then it fades out, so obviously its not a problem of a flakey input.. sheesh.

Reply to
Derwin

In other words you wanted someone to walk you through a complete repair? That's a really rude remark especially when you are seeking FREE help. I've been working on tube stuff since back when that's all there was my friend.

about

Surely you jest. You mentioned spaghetti first so by your logic, you made the first racist remark.

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Reply to
Meat Plow

It does not work now....

So troubleshoot it and find the problem. The small difference in capacitor values you replaced is 99.999999999999999999% likely not to be the problem.

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Reply to
me

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Reply to
**THE-RFI-EMI-GUY**

Have you ever seen a 0.050uF polarised cap ?????

Puh-leeeze !

Graham

Reply to
Eeyore

But the problem is we don't really know what he did.

He mentions those capacitors because he couldn't get the exact value, but he said he recapped the receiver. That implies he changed all the capacitors.

It would have helped if he'd said why he did the recapping. Because there was an existing problem, and he hoped it would fix it? Because he wanted to "improve the sound"? Because he figures they are old enough that they ought to be replaced?

From what he's said, we don't really know if the problem is due to the recapping, or existed before.

Michael

Reply to
Michael Black

He had mentioned he did so because the audio had a "Squishing" sound to it. So - I suppose we can take that as he was trying to correct for an audio issue .

Reply to
Radiosrfun

Old equipment wiring does look like spaghetti compared to PCB construction. :)

DId he replace the electrolytic caps as well?

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Reply to
Sam Goldwasser

In message , Derwin writes

Hmm, let's think about it for a moment, it worked before you screwed with it, you screwed around with it, it doesn't work now... Anything leap out at you? Ten points if you came to the same diagnosis as me...

Flakey downright rude tinkerer IMHO.

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Reply to
Clint Sharp

It is common practice for people who restore antique radios. Lots of the paper insulated capacitors are leaky, so the shotgun that problem before they damage tubes and other parts from improperly biased tubes. The extra current can even fry an old power transformer. That was why I recommended the news:rec.antiques.radio+phono newsgroup. Its an excellent source of parts and information for this old radios. There are also people there that make reproductions of hard to find parts and knobs.

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Reply to
Michael A. Terrell

Obviously what you did caused the problem. Check for cold solder joints and inadvertent connections via solder flash. If you have enough information (e.g. a detailed log of what you did, or before/after photos), go back and recheck your work.

Did it look like spaghetti before you started?

From your description, it sounds like maybe it's drawing more current now than before, so that the power supply capacitors are no longer adequate. Does it have a rectifier tube in the power supply? Is it glowing red? Perhaps you've dramatically changed the bias point in the output stage by some misconnection.

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Reply to
CJT

I'm not arguing against the practice, just pointing out that why someone does it might help define where the problem lies.

If there was an existing problem, the capacitors just might not have been the problem.

If there was no problem, but now there is, then it's indicative of some issue related to the replaced capacitors (though obviously it can always be some coincidence that something else failed at this moment).

It's not going to be due to those .068uF capacitors because their value is different, but obviously it could be a bad electrolytic replacement, or perhaps a reversed electrolytic. It might be a coupling capacitor that turns out bad. It could be that in the spaghetti the poster overlooked a capacitor that ends up being the problem.

It's obviously easy to shotgun replace parts when something fails, but if that doesn't solve the problem, nothing's been done to figure out where the problem lies. As it now stands, the capacitors have been changed and there is still a problem.

Michael

Reply to
Michael Black

Hi!

Perhaps you have a new capacitor that is bad? It is unlikely but *does* happen. A check would be worthwhile and won't take too long.

There could be a bad cap, or another component that failed. You will have to do some testing of the unit.

Yes it can. If you still don't agree, stop and think about the the construction of most audio amplifying equipment. Many power amplifier/receiver units have multiple inputs that may be selected. All of them lead to the same place, but before they are merged, each one is a separate circuit...and a fault could develop in the circuitry that is unique to each input. If you haven't tried this idea, hook up your audio source to another compatible input. For example, if you're using a tuner as an audio source, you could hook it to any of the tuner connector, tape connector or even the AUX connector. On most equipment they all use similar signal levels and characteristics.

Please take the suggestions you receive seriously. No one here can see your workbench or know some of the things you know about the equipment you're working on. For that reason, we *have* to cover the basics in an effort to get on the same page that you are on.

William

Reply to
William R. Walsh

Sounds like you got an electrolytic cap in backward. They are polarity sensitive.

Bill

Reply to
Bill Jeffrey

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