Intermittent drop-out and crackle at low volume

[Sophie424]

My Onkyo integrated amp tends to suffer from intermittent drop-out and mild crackle at low volumes; I have not noticed it happen at higher volumes, and it is mostly in one channel.

Also the drop-out does not seem to happen on the headphones-out jack.

What should I suspect, and what might I try to diagnose and fix? I can handle a soldering iron, but am otherwise not an electronics heavy-weight :-) Finding and re-soldering a cold-solder joint is probably OK, but finding diagnosing a bad transistors and swapping out for an equivalent is probably beyond me.

Thanks for any pointers!! -- Sophie

[Sophie424]

ummm .. bumplet ?

[Steve Dunlap]

Originally posted by Sophie424
My Onkyo integrated amp tends to suffer from intermittent drop-out and mild crackle at low volumes; I have not noticed it happen at higher volumes, and it is mostly in one channel.

Also the drop-out does not seem to happen on the headphones-out jack.

What should I suspect, and what might I try to diagnose and fix? I can handle a soldering iron, but am otherwise not an electronics heavy-weight :-) Finding and re-soldering a cold-solder joint is probably OK, but finding diagnosing a bad transistors and swapping out for an equivalent is probably beyond me.

Thanks for any pointers!! -- Sophie

Possibly a bad contact on the output protect relay. The headphone output would be taken before this a would not be effected. The other possibility is a cracked solder connection in the same general area. Either of these would show up as you have described at low volume. At higher volume the voltage breaks over and the sound comes back. Try cleaning the relay contacts with a burnishing tool (a really fine file) and then flush with a cleaner. For a cracked solder connection you just re solder the cracked connection.

I hope that helps some.

[mjf]

hello.
if it is a headphone jack that switches the speaker or the headphones you can clean these contacts too.
greetings...............

[Sophie424]

Thank you, Steve, mjf ! I will inspect and see if these will fix it.

[Sophie424]

Amp opened up, pondering getting under the circuit boards.

One more question -- the amp has A and B speaker outputs (and a switch between them). I see the 2 output protect relays labeled RL351 and RL352, but they look like tightly sealed little boxes. The headphone does switch off the speakers, but that bit of stuff appears a bit harder to access.

The crackle shows up only on A or A+B, not on B.

Any narrower suggestion? Should I try to open out the relays to clean them?

[AndrewT]

bypass the A+/B switch and run the speakers direct from the relays.

If the problem goes away then the switch is faulty.

If the relays are after the switch, then tap in before the switch, but be careful, you have also bypassed the relays.