A-1 buzzing when I touch the volume knob?

[Mat86]

Title verbatim, when I touch the volume knob on this I get a buzzing noise through my speakers. I noticed this when I first got the unit and now that I've done some work on it and fired it up again, was reminded the issue's still there. (The A-1 in particular has a weird pot where the balance 'knob' is on the same shaft as volume and moves with it)

Symptoms:

• Buzzingly occurs when hand on the knob (or shaft), but with the volume at around 7/10 and not touching, I can hear a similar feint buzz out the speaker still
• Buzzing completely stops when volume goes over 90% (same with the no-touch buzzing, gone when volume maxed)
• Seems like it's in both channels, but when I use the balance function, it stays in the right speaker regardless which channel I adjust balance to.

How do I go about solving this? Thankfully the faceplate is off and not fully buttoned up so I still so I can poke around some more


Bonus issue: I noticed while testing that when I turn the balance knob to the right, volume goes up in my left speaker, and if i turn left, right gets boosted. How could my channels be backwards? As far as I can tell, no one else has worked in this unit before or messed around in here. I'm leaving everything dead center anyway, but, this is weird.

 

[avionic]

Bonus issue: I noticed while testing that when I turn the balance knob

There is no balance control per say. They are independent L & R volume controls. Varying the left or right volume facilitates a balance control.

 

[avionic]

Buzzingly occurs when hand on the knob (or shaft),

Flip your AC plug 180° ... See if it clears up.

 

[Mat86]

There is no balance control per say. They are independent volume controls.

yeah its hard to describe...and use. That might explain the bonus balance question, I'll have to put the knob back on, just finished prying it off.

 

[Mat86]

Flip your AC plug 180° ... See if it clears up.

No dice.

 

[avionic]

Is the hex nut securing the dual volume control to the metal chassis tight ?

 

[avionic]

Poor solder connection on the dual volume control is another possibility.

 

[Mat86]

Poor solder connection on the dual volume control is another possibility.

I didn't notice anything when I was in there looking for joins to reflow, nothing spotty when I put pressure on the board

Is the hex nut securing the dual volume control to the metal chassis tight ?

Something related! The nut alone wasnt doing anything, or nut plus washer.....I then reseated and put back every single case screw, and no luck, and then got frustrated....decided to change sources just to test the phono while I was sitting there and magically it went away. Went back to Aux and its fine now. Removed the volume hex nut and it started buzzing, so that's key I guess

thanks

(weird that it had this issue before disassembly too, i guess something was loose then too)