Popping in left channel

[NishBtl]

I completed building my Stereomour kit a couple weeks ago, and it's been running great. Last night, as I went to turn it off there was a loud pop that came through my left speaker when I placed my finger down on the aluminum plate near the power switch. I pressed down on the plate again to confirm what I had heard, and it "popped" again. I turned off the amp and unplugged it to see if I could see any areas that might be shorting against the plate, but didn't notice anything.

This morning I turned on the amplifier again to see if I could replicate it, and I wasn't able to get the same result. It seems that it must have something to do with the length of time the amplifier has been running and how warm the unit gets.

Has anyone else experienced this same issue? Any ideas on what I should look for in the circuitry underneath?

Any help is greatly appreciated.
Thanks.
-Mark

[Paul Birkeland]

Last night, as I went to turn it off there was a loud pop that came through my left speaker when I placed my finger down on the aluminum plate near the power switch. I pressed down on the plate again to confirm what I had heard, and it "popped" again. I turned off the amp and unplugged it to see if I could see any areas that might be shorting against the plate, but didn't notice anything.

Check the middle lug of the hum pot.  These can get close to the chassis plate, and if this lug is allowed to contact the plate, nothing good will ever come of it.

-PB

[NishBtl]

Center lugs of hum pots look fine.
Any other ideas?

[Paul Birkeland]

Loose solder joints.

If you tap on the plate while the amp is running and this produces popping, then something is loose inside.

[NishBtl]

Very strange - I ran the amp for several hours yesterday afternoon. After several hours of listening, I pressed on the top plate again to see if I could recreate the popping and couldn't. I guess it's good that I wasn't able to force it to "pop", but it just makes me more confused. Fingers crossed that I don't run into this issue again.

[rlyach]

This may be totally from left field, but did you notice any static spark when you touched the amp when it popped. In cold weather static charge can build up and a spark to the grounded plate will cause a noticeable pop. Also, most people won't feel, hear, or see a spark up to about 2000V static charge. If this is totally stupid, forgive my post. Part of my job is dealing with static protection for computer chips.

[Paul Birkeland]

Part of my job is dealing with static protection for computer chips.

I had this vision of you laminating the chassis plate of your Stereomour with one of those clear anti-static bags with the black stripes.  Could be a fun look?

[NishBtl]

Nope, there was no spark. Really weird. Just hoping I don't run into the issue anymore.

[Natural Sound]

This may be totally from left field, but did you notice any static spark when you touched the amp when it popped. In cold weather static charge can build up and a spark to the grounded plate will cause a noticeable pop. Also, most people won't feel, hear, or see a spark up to about 2000V static charge. If this is totally stupid, forgive my post. Part of my job is dealing with static protection for computer chips.

Good call! I live in the desert SW so it's dry most of the time. I am in the habit of touching something metal that is grounded prior to touching any of my electronics. I've pulled some pretty impressive arcs discharging myself like that. There is usually a small "pop" during the discharge. That "pop" is louder if I forget an touch my FPIII first. The fact that I'm using Goldpoint stepped attenuators with metal knobs doesn't help. Static electricity raises he'll with my vinyl records as well. Running a cool mist vaporizer helps a lot.