Near-total loss of left channel fixed by cooldown

[dpitch40]

After a long session of running my amp, the left channel suddenly went almost (but not completely) silent. I shut it off and let it cool down (it was quite hot by this point) for about 10 minutes, then turned it back on it and it sounds fine again. Should I be worried about this?

[4krow]

I don't about worried, but it seems that you might have what we used to call a high open in a wire. That happens when the wire inside of the insulation is broken, and only held together by the insulation. I have seen it go both ways. Usually when the wire heats up, it expands causing the connection to be made.  I don't have an explanation for the opposite happening, but I remember seeing it before. Either way, you are inconvenienced, and the problem should be dealt with. Was only the left channel getting too hot? If so, there may be a different explanation.

[Grainger49]

If it is what Greg above thinks it is you can try the "chopstick test."  If you have a chopstick, or an insulated non-metal probe, start it up and listen.  Flip it so you have access to the terminals and wires and start probing the terminals in the problematic channel.  Also use it to wiggle the wires back and fourth. 

[dpitch40]

It just came back even with a cool amp. Then I shut it off for a bit and it's working yet again. With the chopstick test, what am I checking for--wires that appear internally broken? Couldn't I just test the resistance over each section of wire?

[Grainger49]

If you poke a cold solder joint or an internally broken wire it will cut out and come back.  If the wire is pushed together cold it will "ring out" fine.  That is why you poke it to see if it breaks continuity.

[dpitch40]

Fortunately, I found the problem immediately. Unfortunately, it appears to be the white wire in the 3-wire braid, so replacing it will be...inconvenient. The sound in the left ear indeed cuts in and out as i poke it. (I assume it's the white wire and not the other two in the braid; I will check before removing) Thanks for the help.

EDIT: Put in a new white wire. Did the chopstick test again. It is fine when I bump it, but I discovered it cracks/pops very loudly when I push the braided white wire sufficiently off-center. Is this anything to worry about?

[4krow]

square one again. Sounds it's not over till it's over. The wire making the popping sound is still a culprit to be rekoned with. I have had the same problems with certain types of wires that don't take kindly to bending more than once. Then it's just better just to replace them and get it over with.

[Paul Birkeland]

I'd look at the ends that the white wire connects to, maybe more on the pot end than the jack end.  You likely have a fussy joint there.  I'd also inspect the pot itself to be sure everything looks in tact.

[dpitch40]

I used the last of my white wire on that fix, so I'd have to get more. I redid the solder joints on it and they are both very secure. Also, is it normal to hear a very quiet high-pitched whistling sound from the amp? (Possibly from the tubes)

[Laudanum]

Im assuming you hear the noise externally.  In other words, just from the amp itself.    If so, possibly one of the electrolytic capacitors or maybe the Transformer.  I'd doubt the transformer considering how they are customs, better built than off the shelf units, but it's possible.   I have a Hammond in another amp that chirps sometimes, and years ago a torroidal type in one of the better quality car audio amplifiers that also did.  You'd have to pinpoint where it's coming from.  Im sure one of the more techie gents will have more insight and other possible causes.

[dpitch40]

I am getting some soft pops and hisses in the left channel when not playing any music...I can get some more wire to replace the white again tomorrow.

[Grainger49]

With the continuing problem you have, and if you have located it to the input wiring, I would replace all three wires.  It will make the braiding much easier.  It will also take less time to do all three than weave one wire into the other two.

[Laudanum]

If you havent already you may also want to try a different 6080 and 12AU7 for those pops and ticks in the left channel.   Tube swap is always the easiest thing try first.

[dpitch40]

I got some 16 AWG stranded wire which was much easier to weave in. However, I am still getting some of the hissing and popping after turning the amp on. It seems to disappear after a minute or two. Again, it's all in the left channel, so the other two wires seem fine. I'm starting to wonder if something is wrong elsewhere.

[Doc B.]

That sounds like a tube settling in. Unless it gets worse I would just wait two minutes before listening.