Distorts after about twenty minutes

[GeneZ]

All experts,


I have an Adcom GFA-535 that sat in my closet for years. Perplexing. It will play fine for about fifteen to twenty minutes, and then the sound begins breaking up. Possible causes and fixes? Thanks, Gene

[digits]

can of compressed air to find the hot component?

[Michael Bean]

I owned several of these years ago, had the same problem. Two of the three I had developed bad/bulging power supply caps, they are the blue 6800uf@80volts that say Adcom on the side. Replacing them fixed the problem, then I sold one and parted out the other two for other projects. Never really liked the way they sounded. Also cleaning them up to make sure there is sufficient air flow for cooling can't hurt.

Mike

[Michael Bean]

Oh yeah, should have added, I also had trouble with RF sneaking into speaker wires on those things, and they really didn't like highly capacitive loads. I think it was because Adcom didn't the inductor/resistor on outputs, most likely a marketing ploy. I fixed those issues by putting about ten turns of 18 guage enameled wire around a 2 watt carbon composition resistor, and placing between the PC board speaker outs and the rear speaker connectors, I also eliminated the front speaker selector switches because they got noisy. Hope this helps.

Mike

[c2cthomas]

Make a nice case for a DIY project.

Build up your amp of choice and toss it in. Errrrr - that is AFTER you have gutted the parts outta the current amp of course.......

[GeneZ]

Originally Posted by Michael Bean

I owned several of these years ago, had the same problem. Two of the three I had developed bad/bulging power supply caps, they are the blue 6800uf@80volts that say Adcom on the side. Replacing them fixed the problem, then I sold one and parted out the other two for other projects. Never really liked the way they sounded. Also cleaning them up to make sure there is sufficient air flow for cooling can't hurt.

Mike

Its quite old... think I bought it in 89-90. Sat in the closet for years after having only about six months use. Guess it just goes at this point. I am not technically inclined, but I knew others here would have the answer. Glad I asked.

Thank you everyone!

[digits]

electrolytics are probably all past their shelf life.

[GeneZ]

Originally Posted by digits

electrolytics are probably all past their shelf life.

Oh no... been saving an imported Grant tube/mosfet integrated for a bigger system when I finally get the space. Sounds like I would have to have that redone by a tech before actually using? Been saving it like vintage wine.

[GeneZ]

Originally Posted by digits

electrolytics are probably all past their shelf life.

I was once advised to leave equipment on to idle when not in use. This was in regards to tube equipment at that time. Does leaving equipment on to idle prolong the life? Are capacitors to be used, or they spoil?

[Mooly]

Leaving equipment on can only shorten its life. Electroylitic caps dry out and any temperature rise speeds that process up. Resistors that are run well within their ratings and are of good quality (ie metal or carbon film not carbon composition) essentially last indefinitely, same for semiconductors and IC's. Tubes will wear out too as the emission decreases.