Pots Behaving oddly on both units of double build.

[steveyraff]

Hey all,

I built this one a few times before. Its a germanium bass fuzz pedal. I have two that need finished by tomorrow for someone who bought them.

Pots are behaving strangely on both units, which is frustrating as I've build this pedal about 3 or 4 times before and never had any issues.

Seems to be happening on the volume pot for both. Its a 50k Linear pot, the same kind used on both, both new pots I ordered from Bitsbox. The problem seems to happen at the extremities - when I turn it up full, but apply a bit of pressure where it can't turn anymore, it cuts out (dry signal only). Sometimes it stays out until I again try to push it further than it will go and it'll come alive again.

Its very frustrating. Checked all my wiring, soldering etc several times over - all is fine.

Steve.

[steveyraff]

Actually on one build its doing it moreso with the Fuzz gain pot, which is a B500K....ugh!

[samhay]

Are the pots rotating and shorting out against something?

[steveyraff]

Are the pots rotating and shorting out against something?

I checked that. I've them secured nice and tight - they are not revolving. I am guessing it is a problem with the inner wiper making contact with something? Its hard to describe. The fuzz gain control for example - sometimes when I turn it to its maximum position, it cuts to dry signal - then no matter where I set it, the signal stays dry, until I try to toggle it around its maximum setting again and it cuts back it. The same happens the other pedal, but with the volume control. Grrr....

[steveyraff]

... Weird. Maybe its dirty - I used the extremely scientific method of blowing in and around the pot as hard as I could. Now I can't get it to cut out again at max position, however now its doing the same at minimum position. So annoying!

...and no, unfortunately I don't not have any spares left of that value, nor do I have the time to order more.

[Govmnt_Lacky]

Sounds like you might have some tiny fragment inside the pot(s) that are causing it to short. If you are blowing air into them and it changed, odds are you moved the unwanted bit so that it effects it another way.

I say replace the pot(s). Better safe than sorry. Especially for a commercial build. 

[steveyraff]

Sounds like you might have some tiny fragment inside the pot(s) that are causing it to short. If you are blowing air into them and it changed, odds are you moved the unwanted bit so that it effects it another way.

I say replace the pot(s). Better safe than sorry. Especially for a commercial build. 

I know you are right, but I don't have any B50k pots left. I do have a few A50k ones though.

[steveyraff]

Just had a thought.

I was looking at which pots were behaving oddly, and which weren't. Trying to think of differences between the two. Then I remembered something different I did.

Is there any way that the potentiometers behaviour can change due to how they are secured to the casing of the pedal?

When I was putting these together, I noticed the shaft lengths of some of the pots I had bought were different that the others. Instead of cutting the shafts, I added some washers to the shafts before putting them through the drill holes. This left very little threading out the other side to secure them, so I used nuts without washers on the outter surface of the pedal. It means that some of the knobs are pretty tight to the casing as well.

Would this in any way be a cause of problems?

[samhay]

> Would this in any way be a cause of problems?
Pretty easy to find out - unbolt them and see what happens.

[steveyraff]

> Would this in any way be a cause of problems?
Pretty easy to find out - unbolt them and see what happens.

Just did. Took washers out from behind it, put it through the drill hole and places a single washer on the outside then fastened it with the nut. Seems fine now actually. There is a tiny bit of scratching on some turns, but its not cutting out to dry signal anymore. Hmm... now I am unsure if its because I blew in it and moved it around a bit, or if it really is to do with the nuts/washers/contact with the casing etc. I guess I'll try doing the same to the other dodgy pots and see what happens. Only problem now is aesthetic really - the knobs are sitting a bit uneven if looking at the pedal side on.