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Thread: Help with bad RCA connections on integrated amp

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    Help with bad RCA connections on integrated amp

    I have a Proton 520 Stereo integrated amp which was working fine until recently, when one of the channels would begin sounding distorted. I found that wiggling the RCA input jacks would sometimes make it go away, but sometimes not. Swapping out RCA connect wires didn't make any changes, and neither did moving it to another input. On all inputs (Tuner, Video, DAD, Tape), it has the same problem. I opened up the unit and used a multimeter to test for continuity between the RCA jacks and the solder connections on the board, and found continuity on all connections. I guess that makes sense since there's some signal going through, but it's just not sounding clean.

    Any suggestions on how to fix this? Should I just melt the solder on all the RCA connections, hoping that when it re-hardens, there's a better connection?

    Thanks in advance.

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    "Thermionic Apocalypse" -JT nickb's Avatar
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    If it affects all inputs the problem it's not so likely to be the jacks. I'd give the input select switch a good workout with contact cleaner.

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    Last edited by nickb; 04-29-2018 at 08:08 PM.
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    Quote Originally Posted by nickb View Post
    If it affect all inputs the problem it's not so likely to be the jacks. I'd give the input select switch a good workout with contact cleaner.
    Thanks for the suggestion - I tried that to no avail.

    I can't seem to get the issue to go away at all now, which makes me wonder if there might be something happening beyond or in addition to a bad RCA connection. I noticed some discoloration around several resistors (see photo) near the inputs - could this have anything to do with it?

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    "Thermionic Apocalypse" -JT nickb's Avatar
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    I see **don't** any thing there that would concern me. Take an insulated chopstick or similar and try prodding and tapping different places to see if you can find something that is not making good contact. You can also remove the links on the back that feed the preamp to the power amp. Try feeding your signal direct to the power amp and see if it is distorted.

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    Last edited by nickb; 04-29-2018 at 10:53 PM. Reason: **don't** typo
    Experience is something you get, just after you really needed it.

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    Quote Originally Posted by nickb View Post
    I see any thing there that would concern me.
    I assume you mean you don't see anything...

    Quote Originally Posted by nickb View Post
    Take an insulated chopstick or similar and try prodding and tapping different places to see if you can find something that is not making good contact.
    I tried this and wasn't able to uncover anything.

    Quote Originally Posted by nickb View Post
    You can also remove the links on the back that feed the preamp to the power amp. Try feeding your signal direct to the power amp and see if it is distorted.
    Fantastic suggestion - don't know why I didn't think of that myself. It still is distorted in the L channel when a source is hooked directly into the main in. So I guess that rules out the preamp section. Also I make the problem worse by wiggling the RCA jack on the L main in. It goes from distorted normal volume to distorted much quieter - like 20% volume. But I can't make it sound good by wiggling it. Perhaps this is issue with the electronic components, in which case I'm over my head. Unless anyone has an idea, I may need to have a pro look at it. Thanks for your help!

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    don't forget the joker g1's Avatar
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    There was a time when wiggling the rca connections cleared the problem (post #1). It looks to me like all the rca jacks are connected to the board, and wiggling one of them may be putting pressure on the board in general. Have a close look at the solder at the left main in jack, or just resolder it. See if that solves the distortion, or just clears up the volume drop issue.

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    VICTORY! I was about to resolder the main in jacks when I noticed that the solder connections had come loose around some of the main transistors. Since they're connected to an off-board heat sink, when the circuit board flexed, it worked the connections loose. I resoldered them and everything's like new. Thanks for the help, all!

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