My Pot Problem ...

[Kregg]

The volume pot on my v-champ clone works fine. However, if I tap on the knob it's like hitting an open mic and the volume swells a bit.
Does anyone have a diagnosis?

[Structo]

Kregg the first thing I would do is try a different pot.
Or try reflowing the solder joints on it.

Is it scratchy at all when you rotate it?

This is a Vibro Champ right?

[Kregg]

Yup, it's the Vibro Champ and it's fine when I adjust the volume. I put in the Alpha's that came with the kit, even cleaned them before I fired it up the first time. Figured it was just a crappy pot. I'll probably replace it with a P.E.C.; I've never been keen on Alpha pots.

[sliberty]

Could just be a microphonic V1 tube. Try swapping a few different tubes in before you heat up the soldering iron.

[Structo]

That is true since the vol pot is feeding the grid.

[sliberty]

It's not necessarily because of an electronic connection to the tube. It could simply be the physical proximity to the tube. You make the chassis vibrate when you tap the pot, and the vibrations are trnsmitted to the tube nearby.

[funkmeblue]

I've had the microphonic tube problem as well. It was more of a static sound or scratchy kind of sound when I touched the knob without turning it.

[Kregg]

Tubes are fine. I'll put in a new pot this week and report back to you with the results.

[jelle]

Check grounding as well.

[karmakim]

Measure the DC voltage over the pot. If there is.. you have a leaking cap somewere

[Kregg]

Thanks all. No, my meter isn't picking up anything out of the ordinary.

That said, my trusty old meter crapped out and I'm using an autoranging MM that I picked up a few years back.

[Kregg]

In ... Out ... Done!

It was definitely a crappy pot. I changed the Alpha out with a P.E.C. and presto no freaked out volume surges when I tapped the knob. I should've changed them all.

[sliberty]

Glad you got it solved.

BTW - I use Alpha pots all the time, and like them a lot. I have found them to be reliable, and like their feel. And they are certainly inexpensive.

Steve

[Noel Grassy]

Glad you got it solved.

BTW - I use Alpha pots all the time, and like them a lot. I have found them to be reliable, and like their feel. And they are certainly inexpensive.

Steve

No foolin'? Do they offer a 2 watt pot?I see them in quite a few boutique amp builds and am surprised. They are inexpensive and that may relate to materials as well as manufacturing costs.
I used to use them in my FX pedals but have since switched to Alps 9mm pots.
That same nice feel rotationally and 3yo pedals have yet to get scratchyness or
other miseries. YMMV...

NG.

[M Fowler]

Anyone besides me using Bourns pots? I haven't had any problems.

Mark