Post Number: 22
|Posted on Saturday, October 28, 2006 - 10:44 am: |
I just took delivery of a used Alembic set of pickups and electronics for a stratocaster. Wowie Zowie baby. The volume pot suffers from a little scratchy syndrome. I read in another thread that the Alembic pots are "self cleaning" and to simply exercise the living daylights out of them and the scratch will go away. Well my wrist is getting tired. I have some contact cleaner with lubricant (white mineral oil) that I have used with great success on other scratchy pots. Is there any reason why I shouldn't squirt some of this in my Alembic pot? Thanks for your help. JBY
Post Number: 1750
|Posted on Saturday, October 28, 2006 - 12:02 pm: |
I believe it is a closed pot. Your contact cleaner will only coat the outside. making a mess, but will have no effect on the internal workings of the pot. Of course I could be completely wrong. If so, I'm sure someone will chime in soon to set me straight.
Post Number: 23
|Posted on Saturday, October 28, 2006 - 1:18 pm: |
What about down the shaft? I wonder if I can replace just the pot and not the whole assembly?
Post Number: 207
|Posted on Saturday, October 28, 2006 - 10:36 pm: |
The standard Alembic pots are pretty premium stuff - sealed (although not totally) and self-cleaning. If the body of the pot is rectangular and blue or black in color, these are also high-precision pots with a plastic conductive element.
The way the pot works is that there's a metal arm (the "wiper") connected mechanically to the shaft and electrically to the center terminal. The wiper sits on a conductive element who's ends are connected to the other two terminals on the pot. The greater the distance between the wiper and an end terminal, the greater the resistance. The conductive element is usually a molded piece of carbon. The fancy plastic conductor pots use a conductor made of special plastic which is trimmed with a laser beam so the resistance change is very precise.
When dust gets on the conductive element, you get dead spots, and scratchy noises. With regular pots, it's easy for dust to get in the case, although it's not usually like a dust storm flying around in your control panel. With the fancier pots, there's no openings in the case and the really fancy pots even are sealed around the shaft so you could use them underwater.
In the better pots, the wiper is shaped to push dirt off the track when you turn the pot a lot. Sometimes whatever got in there just won't come out.
The easiest fix is just to replace the pot. You probably want to contact Alembic for an exact replacement, even if it's kind of expensive. You could put in a regular old DiMarzio pot in a pinch, but it might not fit in the space of your OEM pot and you may have trouble fitting the knob on too.
I wouldn't blast contact cleaner in there if you have a rectangular pot. The oil in there might eat up the conductive element. You may find a blast of compressed air down the shaft (even from one of those air duster cans) might help, but if it doesn't work, just replace the pot.
Post Number: 24
|Posted on Sunday, October 29, 2006 - 7:23 pm: |
David, thanks for that detailed explaination. I am glad I didn't just attack the pot with a spray can :-) Now here is where it gets weird. When played through my Traynor YGM-3 (1976) there is a consistant spot in the middle of the range, where it gets scratchy, but when I plugged it into my Dean Markley RM150DR, there is no scratchy symptom. The Traynor seems to function perfectly in every way, (except for the bass pot which is a little scratchy), I just retubed the entire compliment. Any ideas what strange and sinister forces may be at work here? Thanks, James
Post Number: 3718
|Posted on Monday, October 30, 2006 - 6:40 pm: |
The Traynor is proabably injecting a small DC potential.
Solutions? Add a capacitor in series with the signal wire from the Traynor. Something like a 50 nanofarad (.05 uF) is a good place to start, the value isn't that critical. If you email me with your mailing address, I can get you a physically small one.
There's three choices where to add the cap:
1. Inside the cord. This is sweet since you don't have to modify the guitar or the amp - just don't lose that cord!
2. Inside the guitar. In series from the purple wire to the tip contact of the output jack
3. Inside the Traynor itself in series between the tip of the jack and the wire that goes to the rest of circuitry.
With DC injected, some pots are more sensitive than others, so replacing the pot might help reduce the noise, but modifying like described should eliminate the trouble.
Post Number: 27
|Posted on Wednesday, November 15, 2006 - 7:24 pm: |
Thanks Mica, I got the cutest little cap in the mail today, taped to a beautiful postcard. I will let you know how it goes.