DiMarzio Model PJ's controls not working properly

JimmyM · #1 02-20-2013, 08:53 PM

I have this cheapo pieces parts PJ that has Model PJ's on it. Last week I decided to go with a new set of strings that required a truss rod adjustment (D'addario balanced tension XL's 40-95 if anyone gives a rat's ass). Had to take off the pickguard, and accidentally yanked the hot wire of the J loose from the stacked volume pot it's wired to.

Soldered it back to the middle lug of the correct pot and it works again, but a strange thing now happens when I use the volume knobs...when only one knob is on full and I turn the other knob up full from a lowered setting, it crackles at the point the pickup is turned up full. It also happens if I turn down one pickup when both are on full...as soon as I start to turn one down, it makes a crackling sound as soon as it reaches the point that it's not on full. Never did it before.

Whut I did?

EDIT: I should have made it clear...the crackling only happens at the point in the pot where the volumes are both on full, and it only happens once and then works normally.

Stone Soup · #2 02-20-2013, 09:14 PM

It usually takes a pretty good yank to pull a soldered wire off, so I'm going to say the yank either dislodged some gunk in the pot or you cracked the phenolic and didn't notice it.

It does this with both pots?

EDIT: It's a guess, of course.

JimmyM · #3 02-20-2013, 09:39 PM

Does it with both pickups, but just tried it again and discovered that it clears up a bit if I play around with it, and it doesn't do it at all when I'm not playing. Have a feeling a little Deoxit is all it needs now...will report back as soon as I can find my Deoxit...hopefully it won't be 4 or 5 days

JimmyM · #4 02-20-2013, 09:44 PM

Found it...crisis averted! Never mind...just a simple dirt problem.

walterw · #5 02-20-2013, 09:51 PM

i have seen this on sketchy pots, where they crackle hideously if you have a string ringing while you move it (sending signal through the pot), but are silent otherwise.

usually means time to replace the pot.

JimmyM · #6 02-20-2013, 10:11 PM

Dang it! It came back 10 minutes later. I could probably live with it, because it did get a little quieter, but I have a feeling you guys are right and it's time to look at a replacement soon. Oh well, at least it's a parts bass with no collector's value.

JimmyM · #7 02-21-2013, 01:32 AM

Decided to call shenanigans on this thread. I just tried my 76 Precision which has different PJ pickups and separate tone and volume, and it's doing it, too, and I just used that bass on a gig and it was perfect. Therefore, I'm going to chalk it up to some weird electronics ghost in the machine at my house and forget about it.

jbrew73 · #8 02-21-2013, 04:13 PM

What amp are you using? Could be dc voltage leaking out through the input causing it. Plug a cable into the input and measure across the tip and sleeve of the other end.

walterw · #9 02-21-2013, 09:06 PM

+1

DC voltage across a pot makes it crackle hideously when you move it.

JimmyM · #10 02-22-2013, 12:48 AM

I was going from my REDDI into a FastTrack interface and into headphones. I don't think I'm going to worry about it, though. I think it's more likely interference causing it than a real problem. Didn't use that bass on my gig but I used my 76 that also was doing it last night, and it wasn't doing it on the gig. Haven't had a chance to plug the other one into an amp yet, but I think I just had something weird going on with the electricicals.

joelb79 · #11 02-22-2013, 02:50 AM

Quote:

Originally Posted by JimmyM

Whut I did?

Meddle · #12 02-22-2013, 04:36 AM

Maybe check the wire you re-soldered. I had this problem with a bass and it turned out I had slightly 'bird caged' one of the wires, but it only caused crackling and distortion when the mounting plate was screwed right down and the wire's angle to the pot was a certain way. A single copper strand was snaking away and brushing a ground point somewhere on the pot. Took me hours to find that!

JimmyM · #13 02-22-2013, 10:25 AM

Quote:

Originally Posted by Meddle

Maybe check the wire you re-soldered. I had this problem with a bass and it turned out I had slightly 'bird caged' one of the wires, but it only caused crackling and distortion when the mounting plate was screwed right down and the wire's angle to the pot was a certain way. A single copper strand was snaking away and brushing a ground point somewhere on the pot. Took me hours to find that!

And it's absolutely a possibility with my lame soldering!