NEED HELP w/ Vintage Hi Fi Restoration

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warmvoice22

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Hi Everybody,

I was looking for a new amplifier and speakers for my record player, and came across this piece in a thrift store...(Image 1) (Image 2)

I opened the back to take a look inside and found this...(Image 3) (Image 4) (Image 5)

and this diagram...(Image 6)

and these labels on the back...(Image 7) (Image 8)

...so I plugged in my stereo, plugged the thing in and it sounded great!...for about a minute. Then this part (Image 9) which is also seen in the top left part of image 4 started to smoke, the audio ceased, and little drops of something oily and smelly started dripping out of the part.

I knew I was in for a challenge when I saw the thing, and figured I'd have to get a book and learn how to rebuild it, but I thought someone on the forum might be able to give me some advice in the meantime...

If you know about this kind of set up and can point me in the direction of any good books or websites, or offer some answers yourself, I'd be very grateful...it sounded really warm and nice for the few minutes it worked, and I'd like to get it back to sounding like that or better if possible. Thanks...
 

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Cheap speakers with tiny magnets and a low power vacuum tube amplifier do not make high fidelity.
It was probably made in the 50's.
The power transformer (it is rare today) was smoking and dripping so something (maybe a filter capacitor) is shorted.
The manufacturer forgot to use a fuse so the circuit is a fire hazzard.
 
edit: The chief audio guy already beat me lol!!

The item that started smoking seems like a transformer to me... There are a lot of other guys on here that can help you more, I've never worked with anything that uses tubes. (I'm too young...I've only listened to a record for the first time a few weeks ago!!!)

If you could take a nice centered and clear picture of the schematics it would help.
 
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Thanks, will get the diagram up asap...would appreciate responses that don't talk about how lame my project is or how little I know, would rather hear how to fix this thing, thanks...
 
I don't know where you can buy a 60 years old transformer and high voltage capacitors today.
I made a kit vacuum tube amplifier and FM tuner in about 1961 and replaced them with a transistor receiver in 1964. I still have the 1964 receiver and it still works perfectly.
 
Audioguru likes to poke fun at things he hasn't designed himself
Many times he's right because so many manufacturers cut corners..Hence the no fuse..

I would try not to take it personally.
 
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You've probably killed it by just plugging it in - with antique gear like this you need to reform the electrolytics before use, as they tend to fail because of the years since they were last used.

Just sticking power on it means the caps fail totally, and it could well have killled the transformer as well.
 
Hi,

On the plus side, you are in the right place for advice on this sort of thing.
Most of the people here are familiar with this sort of unit.
Its a standard type old push pull valve amp.

On the down side, its not that easy to repair without experience and appropriate tools.

It sounds to me that the mains transformer has overheated.
Whether or not the mains transformer has failed or it stopped for some other reason is not clear.

If you want to repair it yourself, you are in an appropriate forum, but its a steep learning curve, and for a technology which has been out of mainstream use for many years.

You might do better to get it assessed by someone with the knowledge and experience, to tell you roughly what it needs, and advise you accordingly.

regards, John
 
The issue is evident, something went wrong in the power supply. You should start there.

First of all, disconnect the transformer from the circuit but remember which wire goes where. Then connect it to mains and start measuring. You should get 6.3(+- some value) for the tubes filament and some value above 100/150V. This is dangerous so be careful.

Also put up a more clear picture of the schematic so that we can analyze it in more depth

If the transformer checks out, follow that power path in the schematic and see if some cap is blown out or there is a short circuit somewhere.

This antiques tend to have really nasty caps, and usually if a tube unit isn't used for a fairly good time, the old caps need replacement. When you get it to work again, I strongly suggest that you replace all antique capacitors with new ones with the same values/voltages.
 
I would bin the whole project, it will cost more for a new trasformer, untold capacitor/electrolytic replacement than a whole new amp, and the quality of this unit isnt exactly spectacular. I will rebuild a great old radio for sentimental purposes, but not this pile of low-fidelity junk.
 
 
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