What is it with thirty year old stereo amps?


Old 08-28-05, 02:48 PM
Captain Radish
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Angry What is it with thirty year old stereo amps?

Maybe someone can help me with this as Google isn't very helpful. I have aquired five stereo amps dating from approximately 1965 to about 1978. The only problem I'm having is only one of them works correctly. The other four all have one of the stereo channels out (three of them have the left channel out and the other one has the right channel out). Anyone know what is going on and what I can do about this? I know it's not the speakers because I"ve tried them all on five different pairs. I'm getting rather frustrated with these things.
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Old 08-28-05, 03:33 PM
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All things wear out in time. My 1981 onkyo still works fine. I replaced it only because I wanted surround sound in the family room.

Do these have tubes, by any chance?
Old 08-28-05, 04:21 PM
Captain Radish
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I would say no, but I haven't cracked them all open to look. The one I have handy right here does not as far as I can tell.
Old 08-28-05, 05:36 PM
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What make and model are these amps?

I have been lucky lately at yard sales and have managed to find a Phase Linear and Crown pre-amp as well as Luxman power amp that I could only lust for "back in the day".

Depending on what you have it could be worth looking into having repaired if you can find a sympathetic tech who knows the old stuff.

I too have given in to the surround sound fad but retreat to the dungeon when I need a good music fix.
Old 08-29-05, 08:40 AM
Captain Radish
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The one I'm currently getting frustrated over is an old JVC. The Panasonic I picked up at a Goodwill for $30 is the only one working for some reason. I guess that means I should go Panasonic in the future.
Old 08-30-05, 02:41 PM
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If any of them have tubes, mostlikely the one that is not lit will be bad.
Otherwise the bad units most likely have bad transistors on the channels
that dont work. Depending on how old they are, they might have an STK
package instead of descrete amps inside. Not sure of your technical ability
but the power transistors could be TO3 style that are silver spaceship
looking with 2 legs comming out of the bottom, or black/green plastic
rectangles with 3 legs which usually have a screw in them holding them down
for heat transfer. If it is a STK package it will be a larger black plastic looking
part with about 30-40 legs.
Old 08-31-05, 08:05 PM
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A simple way to tell if the units are tubed is to turn them on and touch the cabinets after ten minutes or so. If they're hotter than anything, they're probably tubed. Too bad you can't go to the TV shop with your tubs and plug them into the tube testing machine any more.
Any way, check also to make the connections to the speaker terminals are clean and contiuous. A continuity checker can help you here. Do any of the units have dual signal strength meters? If one is moving and the other not, this could imply the channel circuit is dead.
I didn't notice where you live, but here in Cincinnati there are at least a half dozen shops that specialize in the old tubers. Much of the top line equipment out there today is now tuber. Audiophiles claim a tuber gives better sound than the all transistor units being sold now. I tend to agree as I blew out my speakers playing J Giels Whammer Jammer on my tuber, but the same record on my new Kenwood doesn't sound as good.
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