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Help diagnosing my left channel not working

Mat86

Mat86

Active Member
So long story short, I have a tube headphone amp that I had a technician recap recently. Set it up on my desk to test it out and first thing I noticed was loud, erratic noise coming out the left channel that would fade in and out intermittently. This settled down after some testing and tube swapping to troubleshoot it, and he told me it was probably one of the new capacitors settling in.

(also when i plugged it in i could have sworn i heard sparks, but saw no evidence, couldn't repeat it, and it never shorted out, so chalked it up to being paranoid)

Couple days pass and it legitimately sounds terrific and better than before, but nitpicking, I notice on startup there's a slight hum still on the left channel that isn't on the right. It was basically inaudible but I was hoping whatever happened on day 1 would be completely flushed.

I leave it to burn in for a few days after using it Monday with no issue, and last night I fire it up and the left channel is completely dead. Right channel is perfectly normal. I try basic troubleshooting and make sure its not the source or a tube or anything like that.

  • during power up and down, i can hear the volume pot scratching, but only in the (working) right side
  • if i remove my Right RCA input, i can hear cross talk from the L RCA source coming into my right driver still if I push the volume high enough
  • It was clean (obviously quiet) audio from the left input mostly, but before typing this I tried again (with only L input in) and had an issue with the noise going crazy again (picked up by the right driver), seemed to be affected by touching the case (grounding?) then went away
  • If I have no sources plugged in, i can tap on the right input tube with a pen and hear the microphonic noise travel through. If I tap the left intput tube it's dead silent
  • All the tubes are warmed up and visually look normal

Based on all of this, does anyone have an idea what went bust?

(wasnt sure if this thread should be in the tube sub or DIY, sorry if i chose incorrectly)
 
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Caps "settling in" don't make loud erratic noises. So seems like something was wrong right out of the shop. My guess is one of the caps in the left channel is now open. In fairness to your tech it wouldn't be the first time a new part turned out to be bad. And it may not have turned bad until it left the shop.
 
dcgibby said:
Caps "settling in" don't make loud erratic noises. So seems like something was wrong right out of the shop. My guess is one of the caps in the left channel is now open. In fairness to your tech it wouldn't be the first time a new part turned out to be bad. And it may not have turned bad until it left the shop.
Click to expand...

so it sounds like 1 of the caps is faulty? nothing else is potentially fried, right?

safe to assume i should go buy one of each cap type in advance to save some time or should I wait?
 

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Mat86 said:
so it sounds like 1 of the caps is faulty? nothing else is potentially fried, right?

safe to assume i should go buy one of each cap type in advance to save some time or should I wait?
Click to expand...
Nope, you should troubleshoot with a meter. It could be an open resistor.:oops:
 
cademan said:
Nope, you should troubleshoot with a meter. It could be an open resistor.:oops:
Click to expand...
thanks; actually that's what the technician just suggested too. fingers crossed. feel a little better that there's a path to fixing it, got depressed thinking my favorite amp just fried itself
 
The tech is responsible to return the device in condition that is no worse than what it arrived in.

Take it back and tell him to make it right. Why put your time and money into a problem somebody else created. The tech may have unknowingly installed parts that were NFG from the factory. It's happened to me.
 
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