tube rectifier "yellow sheet" diode mod - Page 2

telefunking wrote:good morning fellas i have a question,im looking at a st70 its out of state so i cant test it .the seller said he hooked it up.the voulume on one channel was real low.the other channel was fine..as i stated i cant put my hands on it to trace the problem...worst case output transformer? resistor ? and or recterfier tube? output tube?

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Yes.  Any of the above.  A Stereo 70 can be anything up to 56 years old.  It could have been pampered through its lifetime, or played hard and put away wet.  There is no way anyone on this board can diagnose that amplifier with the information provided, especially since the information is secondhand from someone who wants to sell it.

Best assume that he wants to get rid of some problems he's got with it.

telefunking wrote:
any ideas of what i might have to fork out to fix..

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No.

When buying a used amplifier like this, it is best to assume that you will have to put something into it.  Even if the amplifier's circuitry has not developed any problems, tubes have a finite life and you'd best count on replacing the output tubes (the driver tubes last much longer...but getting good replacements can be more difficult).  Since the amplifier does turn on and produce some sound ("fine" to some may mean "rife with distortion" to someone else), at least you know the power transformer and rectifier tube are good.

I know this isn't the slam-dunk, "This is what your problem is and it will cost $2.98 to fix it" you wanted, but it's the reality of buying an old, used tube amplifier.  The purchase of a vintage Stereo 70 is not a "turnkey" deal, like going to the store and buying new equipment.  You will have to put a little of yourself into it, along with a little (or a lot) of your money.

Yes. Any of the above. A Stereo 70 can be anything up to 56 years old. It could have been pampered through its lifetime, or played hard and put away wet. There is no way anyone on this board can diagnose that amplifier with the information provided, especially since the information is secondhand from someone who wants to sell it.Best assume that he wants to get rid of some problems he's got with it.No.When buying a used amplifier like this, it is best to assume that you will have to put something into it. Even if the amplifier's circuitry has not developed any problems, tubes have a finite life and you'd best count on replacing the output tubes (the driver tubes last much longer...but getting good replacements can be more difficult). Since the amplifier does turn on and produce some sound ("fine" to some may mean "rife with distortion" to someone else), at least you know the power transformer and rectifier tube are good.I know this isn't the slam-dunk, "This is what your problem is and it will cost $2.98 to fix it" you wanted, but it's the reality of buying an old, used tube amplifier. The purchase of a vintage Stereo 70 is not a "turnkey" deal, like going to the store and buying new equipment. You will have to put a little of yourself into it, along with a little (or a lot) of your money.

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