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Author Topic: pot problems ...  (Read 3293 times)

add4

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pot problems ...
« on: March 06, 2011, 06:20:28 PM »
Hello
I reopened my guitar today to install a treble bleed, and while pulling one potentiometer out of the guitar, i killed a solder joint so i had to put everything out and start soldering the tone and volume again.
I now have two problems with my pots:
one of the side lugs of the tone pot doesnt seem to work anymore. When i test the omh values between the central lug and the (say it's the left) left lug. it goes from 0 to 500k, but then i test the values between the central lug and the right lug, it says the same thing as when the connectors of the multimeter are apart : >2000k.
It is possible to kill a pot like that?
As of now, i had to rewire the tone pot with the other lug, it works, but the tone control is now reversed, i have to turn it the wrong way to open it.

The volume pot also has a problem : It now acts as a linear pot: it goes from no sound to almost full sound in a 1/10 turn.
the volume pot of the bridge is much more progressive. Is it possible  to make a pot linear instead of logarithmic by buring it? As the guitar was wired a bit specially and i didn't knew where the broken solder joint was i did a bit orf trial and error and soldered a lot on this pot so i might have overaheated it... :(
Any ideas are appreciated.

As i guess i might have to change the pots, details about the type of pots i need would be appreciated too:
I think the pots have to be reverse for the guitars, is that right?
The tone pot is linear and the volume pot is logarithmic, still right?
What about the shaft length and width?
The vol pot reads 'R500k' or maybe it's a 'B' the lower part of the lettre is hidden by the metal part of the pot.
The tone pot reads 'A500k'.
It is for an ibanze AS93 (ES335 copy)
If you have a link for an european seller for the right pots for me that is not too expensive, that would be even better ^^

Thanks for your help.. i am not worrying, but almost... it needs to be working correctly very soon...
Arnaud
Current: Emerald (n), The boss (b)
Had: Manhattan (n)
Wish list: VHII (n), Blackguard 50 (n)

add4

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Re: pot problems ...
« Reply #1 on: March 06, 2011, 07:11:02 PM »
One more question :
I noticed that the tone pot had a lot of solder on its lugs, so i cleaned them and now the lug that didn't worked is working properly.
Is it possible that a short circuit makes the volume pot acts as a linear pot?
Thanks
Current: Emerald (n), The boss (b)
Had: Manhattan (n)
Wish list: VHII (n), Blackguard 50 (n)

Fourth Feline

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Re: pot problems ...
« Reply #2 on: March 06, 2011, 09:34:49 PM »
Just to mention , that I seem to 'hear' a true Linear pot as giving me kind of slope off I prefer on the volume, despite Log being theoretically correct.  

This is so marked, that I bought a load of seperate CTS Linear pots, instead of sets of Gibson style wiring harness kits or packs which usually contain Log Volume pots.   Basically :

'A' stands for Audio ( Log )

'B' Stands for Linear.

You seem to have ( from my re-reading of your original post ) a B500k Linear pot in the volume postions, but prefer the more conventional   A500k.  

Also ( Judging from your photos ) you have purchased a set of Minature pots, whereas it is usually advisable ( from a quality standpoint ) - to gently route the holes out a little larger, and buy 'proper' full size CTS pots, whose thread / shaft is fatter, albeit the same length.  Leave the three way toggle switch as is though, as the body shell will be about 2-3 mm too thick to take a top quality Switchcraft upgrade.

I hope all that helps.

(* Edit * )

With the three semi-acoustic guitars I re-wired, I used to test it all out ( roughly ) whilst the harness was still out of the guitar, by ( gently ) tapping on the pick up pole pieces with a screwdriver. It at least checks how fast the volume fades, and where the tone controls are begin to temper overall tone e.t.c.

If it's any consolation, what you are currently going with all this mullarky, is part and parcel of what most of us went through when we first set out to be home guitar techies. This way, you don't forget.  Wiring a semi-acoustic through the 'F' holes is both a rite of passage - and a labour of love.   :)
« Last Edit: March 06, 2011, 10:02:15 PM by Fourth Feline »

add4

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Re: pot problems ...
« Reply #3 on: March 06, 2011, 10:47:54 PM »
Thanks for your help!
These are the stock pots of the Ibanez guitar. I did not upgrade them. How is it possible to widen the pot holes without damaging the guitar and its finish?

I seem to have identified the problems :
My very bad soldering skills have caused cold solder joints so i soldered the same lugs again and again, and the excess solder was making contact with the top of the pot. I finally had to clean up all the lugs with solder braid, this solved the problem on both pots. I had a (very) frustrating time resoldering everything properly. The solder joint broke constantly while i was fitting the pots into the guitar. I finally got it to work, after (i'm ashamed to say it) 3 hours....
However, i still find the volume pot too fast. The tone pot now does not turn smoothly all the way, after 1/4 turn, there is a kind of resistance in the pot rotation. There is no change in sound, it is just harder to turn. This makes me think that this pot may need replacement soon too.
On top of it all, the solder broke so much that i am not confident at all in what i have done tonight :) i think i'm not done with this.
If i have to redo everything, i will rewire the guitar completely to be sure that everything is wired correctly.

It was interesting, however, i not saw some differences between the BKP shematic and what i have in my guitar.
Ibanez wired the pickup and tone to the middle lug of the volume pot, and the switch to the side lug, while the BKP schematic does the opposite.
Tim also advises to put the ton cap between the right lug of the volume pot and the middle lug of the tone pot, and the right lug is to ground, while on my ibanez, there is only a wire between the middle lug of the tone and middle lug of the volume pot. The tone cap is between the right lug of the tone pot and ground. it is still resistance and cap in serie so it should work the same i think. Same for the volume pot.
It's interesting to see the differences and understand why it works anyway. so i guess it's not too bad.
I also learned to solder ... a little better. But i definately will HAVE to get better at soldering in the future.

Thanks for your help again..
I will think about getting pots from BKP, or maybe stewmac. Do you know what is best?
Current: Emerald (n), The boss (b)
Had: Manhattan (n)
Wish list: VHII (n), Blackguard 50 (n)

add4

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Re: pot problems ...
« Reply #4 on: March 06, 2011, 10:59:28 PM »
So if i understand correctly, theoretically, both the volume and tone pots are supposed to be audio taper?
I thought the tone pot was linear traditionally, but on the BKP online shop, and on the stewmac shop, i can only find audio pots, so i guess audio pots are in fact the common choice for tone control?
This does not explain why the stock volume pot in my ibanez is linear Oo..

Are the mini pots worse in term of quality?
What shaft length should i take? standard or 3/4". i guess it's standard but i'm not sure.

Thanks again
Best
arnaud
Current: Emerald (n), The boss (b)
Had: Manhattan (n)
Wish list: VHII (n), Blackguard 50 (n)