Help With A Stereo Amp

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Help With A Stereo Amp

Postby waldosan » Mon Mar 11, 2013 2:51 am

So my mother runs a consignment store and managed to get a record player and stereo mixed amplifier. I plugged the beast in and it works, mostly, it's especially quiet and i'm thinking some of the internal components are tired.

Anyways; I own it now and I've been trying to get it disassembled so I could at least look at the innards to see if theres anything obviously wrong with it, the only problem that I'm running into is that it's proving difficult to take it apart. the electronics are mounted on a piece of ply-wood, there are screw on the back and on the bottom which i've unscrewed. the plywood didn't budge so i took the nobs off as gently as i could to see if that helped. it didn't. so now i'm wondering if there's some way to get into this particular amplifier that i'm not aware of.

the screws in the back let loose a pressure board panel that showed four more screws and a bar that mounts the banana plugs and rca plugs that the speakers and record player use to connect to it. i tried pulling gently but it did not move, i seem to be looking at it from the backside as i just see a large heatsink and there are no other screws that i can get to inside of the case. the bottom screws loosened the plywood from the actual wooden case but when i tried pulling it out of the case it still would not move.

the amplifier is a general electric series 5000 stereo amplifier. I've tried Google-ing this but came up negative.

i'm hoping that i can figure out the correct way to do this, projects in which i'm taking devices apart very rarely leave the device in aesthetically pleasing states and more often than not in non-functioning conditions and this thing is honestly too beautiful for that fate.
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Re: Help With A Stereo Amp

Postby Jabberwonky » Mon Mar 11, 2013 5:28 am

Can you post some pics? I work better with a visual...
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Re: Help With A Stereo Amp

Postby Atomic » Mon Mar 11, 2013 9:46 am

Yes - Pics would help.

Most of what I've worked with came apart either from taking off the back cover first, or from underneath releasing the upside down U shaped cover (top and sides). Face plate access is rare, depending on the knob/meter/lights setup. The weirdest one hid the screws to release the top/sides cover inside the rubber feet, but it was a small unit.

For what it's worth. Good Luck!
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Re: Help With A Stereo Amp

Postby waldosan » Mon Mar 11, 2013 2:32 pm

well, the good news is that i figured out that the plywood section would come loose just by tilting the entire thing upside down, big coefficient of friction and all that good nonsense. i'll get pictures asap. it's looking like the plywood board electronics are the main power supply and possibly the board that handles signals coming in from the record player. there's another genuine circuit board deeper in the box that i'll try and get to here when i can get back to the project.
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Re: Help With A Stereo Amp

Postby BruceBergman » Wed Oct 08, 2014 2:20 am

Once you get it apart, stick pictures on Photobucket and post links. If you can identify the inner components, that leads to "Sam's Photofacts" wiring diagrams and repair instructions.

A lot of why old amplifiers fail is plain old dried out components, most notably electrolytic capacitors that dry out - The ones in the power supply or audio amp stages go and you'll get tons of hum from 60-Hz power supply ripple. If you don't care about 100% authenticity, the "Orange Drop" Tantalum Capacitors are a drop-in substitution and will last many years. Most other bad components can be tested with a simple VOM, or you can see when they've "Blowed Up Reel Gud."

Tubes go flat. and you need to find someone who kept their Tube Tester in operable condition to find out which ones.

Old school Selenium Rectifiers (the big square plate) go bad (and stink to high heaven when they do) but you can't just drop in a little 1N4000-series silicon diode. The biases and voltage drops are different, and the circuit will need a little re-engineering like a bleeder resistor to work right.
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