Weird fault with P Bass volume, any ideas please?

[Fender32]

Before I get the screwdriver out and start "messing with strange forces that I don't understand" , can anyone suggest what might be causing this problem, please? The bass involved is a brand new Fender Custom Shop '59 Precision ( yeah I know, you'd hope for a little more QC for that kind of money) and here's what it does ...

When the volume pot is turned back from 100% to about 20%, there is almost no drop in volume and then from 20% to zero, it drops very quickly. Then, if the tone is rolled back to around 60% and the volume left on full, it gets stranger . When you then turn the volume down between 90% and 80%, the treble increases and the volume appears to rise, until you get to the 70% mark and then the tone goes bassy again and the volume begins to reduce normally. With the tone full up, or below about 50%, there's no discernable change in the tone as the volume reduces - it only happens around the 50/60% mark . Weird!

So, should I be looking at replacing the volume pot, tone pot, the capacitor, or all three ? There's no way that I can send the bass back, as I'm in Germany, so it's gotta be a DIY fix. What's more, I changed the pickup myself (for a Fralin), so I've probably alreadys invalidated any warranty that it had, anyway. I'm now wondering if excess heat on the back of the volume pot (from my expert soldering ) could have caused some damage, as I don't remember noticing the problem when I first got the bass a few weeks ago!?

Thanks in advance for any helpful suggestions .

[GlennW]

I'd try replacing the volume pot first.

But before that, I'd bypass the volume pot to see how the tone pot and cap act on their own. No need to solder, some short lengths of wire twisted to make the temporary connections will be fine (use tape or something so they don't short out). If the tone circuit sounds ok alone, then I'd replace the volume pot.

[line6man]

Originally Posted by GlennW

I'd try replacing the volume pot first.

But before that, I'd bypass the volume pot to see how the tone pot and cap act on their own. No need to solder, some short lengths of wire twisted to make the temporary connections will be fine (use tape or something so they don't short out). If the tone circuit sounds ok alone, then I'd replace the volume pot.

I dissagree...
If the volume pot isnt working right, its only matter of time before the tone knob craps out too.

I would just replace the whole circuit (shouldnt be more than $10 in parts)

[Fender32]

Originally Posted by GlennW

I'd try replacing the volume pot first.

But before that, I'd bypass the volume pot to see how the tone pot and cap act on their own. No need to solder, some short lengths of wire twisted to make the temporary connections will be fine (use tape or something so they don't short out). If the tone circuit sounds ok alone, then I'd replace the volume pot.

Pardon my ignorance Glenn, I'm hopeless with anything electrical . Whereabouts on the volume pot should I attach these wires and how does bypassing it differ from testing the tone control with the volume wide open? The tone circuit does already work normally on full volume, it's just when you set the tone to 60% and lower the volume that things start to get weird!?

Not trying to be awkward here, just trying to undertand what I'm supposed to be doing !

[line6man]

Originally Posted by Fender32

Pardon my ignorance Glenn, I'm hopeless with anything electrical . Whereabouts on the volume pot should I attach these wires and how does bypassing it differ from testing the tone control with the volume wide open? The tone circuit does already work normally on full volume, it's just when you set the tone to 60% and lower the volume that things start to get weird!?

Not trying to be awkward here, just trying to undertand what I'm supposed to be doing !

If the pot is ok at 100%, there is no need to do any rewiring to test the tone circuit...

when the pot is full on, there should be 0 ohms resistance from the input to output.

There is a resistance, the value of the pot, across the input to ground. the only way that you could remove this resistance is to rewire the input and output together without going thru the pot...
either way, this will not make a very big difference... the tone pot can be tested with the volume at 100%

[GlennW]

Originally Posted by Fender32

Whereabouts on the volume pot should I attach these wires and how does bypassing it differ from testing the tone control with the volume wide open?

There are three lugs on the volume pot.

1) Outside lug bent over and soldered to the pot case; leave that one alone.

2) middle lug; should be one wire that goes to the hot side of the jack. Unsolder that one from the volume pot.

3) Other outside lug; two wires, one is the hot lead from the pickup and the other is a short wire that goes to the tone pot. Unsolder both of those from the volume pot.

Twist or alligator clip the three ends from 2 and 3 together. None of these wires should contact the pot or anything else. This will remove the volume pot from the circuit.

At this point there's no need to screw the control plate back on (less risk of the loose wires contacting something they shouldn't). Lay the bass on its back, plug it in, hit an open string and turn the tone knob. If it sounds like it's working normally I'd think it's safe to say all you need to replace is the volume pot.

I suspect the volume pot for two reasons. 1) it's easy to overheat them when soldering the ground to the back; 2) treble increases when you turn the volume back to 80-90%.

I really don't know how bypassing the volume pot differs from testing it on 10. Pots are resistors, so they're still doing something to the sound when the knob says they aren't. Pots are also funny to diagnose. If it's out of the circuit and everything else is cool, the pot is probably the culprit.

[line6man]

Originally Posted by GlennW

There are three lugs on the volume pot.

1) Outside lug bent over and soldered to the pot case; leave that one alone.

2) middle lug; should be one wire that goes to the hot side of the jack. Unsolder that one from the volume pot.

3) Other outside lug; two wires, one is the hot lead from the pickup and the other is a short wire that goes to the tone pot. Unsolder both of those from the volume pot.

Twist or alligator clip the three ends from 2 and 3 together. None of these wires should contact the pot or anything else. This will remove the volume pot from the circuit.

At this point there's no need to screw the control plate back on (less risk of the loose wires contacting something they shouldn't). Lay the bass on its back, plug it in, hit an open string and turn the tone knob. If it sounds like it's working normally I'd think it's safe to say all you need to replace is the volume pot.

I suspect the volume pot for two reasons. 1) it's easy to overheat them when soldering the ground to the back; 2) treble increases when you turn the volume back to 80-90%.

I really don't know how bypassing the volume pot differs from testing it on 10. Pots are resistors, so they're still doing something to the sound when the knob says they aren't. Pots are also funny to diagnose. If it's out of the circuit and everything else is cool, the pot is probably the culprit.

GlennW,
I really dont understand what you are hoping to accomplish by bypassing the pot...

The tone circuit will remain functional regardless of the volume knobs setting...
All you are doing by removing the volume is brightening the tone a tad.
Even if you turned the volume knob down some, you can still test the tone circuit just fine.

And as i said earlier, if it were my bass, i would just replace both pots to be safe, because pots are only like $4 anyways.

[GlennW]

Originally Posted by line6man

GlennW,
I really dont understand what you are hoping to accomplish by bypassing the pot...

The tone circuit will remain functional regardless of the volume knobs setting...
All you are doing by removing the volume is brightening the tone a tad.
Even if you turned the volume knob down some, you can still test the tone circuit just fine.

And as i said earlier, if it were my bass, i would just replace both pots to be safe, because pots are only like $4 anyways.

What's it look like I'm trying to accomplish by bypassing the volume pot? If it's bypassed and the problem goes away it's a good bet that's where the problem is.

I don't understand your shotgun/replace eveyrthing approach. If you have a flat do you buy a new set of tires?

[line6man]

Originally Posted by GlennW

What's it look like I'm trying to accomplish by bypassing the volume pot? If it's bypassed and the problem goes away it's a good bet that's where the problem is.

I don't understand your shotgun/replace eveyrthing approach. If you have a flat do you buy a new set of tires?

How will you even know if the problem has gone away without another pot...

[Dave M]

Sounds like a possible mis-wiring issue, but possibly an incorrect or bad pot, too.

Check the wiring as it is now, before tearing things apart. The wiring should be very, very similar to this:

http://www.fender.com/support/diagra...190115CPg2.pdf

or maybe (but probably less likely) this:

http://www.fender.com/support/diagra...200_02APg2.pdf

Once you've confirmed the wiring is correct, then look at a pot replacement. However, if the wiring is not correct, fix that then re-test and report back.

[Fender32]

Yep, wiring all appears to be in order.



I've just checked out the spare Fender replacement pots that came free with the Fralin pickup that I fitted and have seen that they are exactly the same as the original pots, currently in the bass . So, I'm a bit less scared about swapping them over now, as it'll still look original afterwards.

However, I think I'll leave the job to someone who's got a bit more skill with a soldering iron, as I don't seem to have mastered my new gas iron yet and it may have been that which caused the problem in the first place .

Thanks again for all of your help, guys !

[Way Off Bass]

you are using a linear taper pot where you need to be using an audio taper pot

or vice versa. i can't remember.



EDIT: also, don't be afraid to go in there and mess around. worse case scenario (providing you don't blow your amp) you will only waste like $10 worth of electronics. One of the best ways to learn is to do

but please, make sure you read your TB threads first! I found the Jazz Shielding thread to be particularly helpful

[line6man]

Originally Posted by Way Off Bass

you are using a linear taper pot where you need to be using an audio taper pot

or vice versa. i can't remember.



EDIT: also, don't be afraid to go in there and mess around. worse case scenario (providing you don't blow your amp) you will only waste like $10 worth of electronics. One of the best ways to learn is to do

but please, make sure you read your TB threads first! I found the Jazz Shielding thread to be particularly helpful

I dont think that any taper would behave that drastically LOL.

But you may be on to something.

I used to like linear pots better because i got used to them, but now that i am used to audio tapers, i prefer them.
The audio taper has a smoother response than linear tapers.

Most pots sold for guitar applications are audio taper anyways, so try the audio taper.

[PanDeVida85]

Hey bro, it sucks you're stuck in this predicament on such an expensive bass.. If I were you I'd leave it to a professional to fix. I personally would dive right in and try to solve the problem after doing the appropriate research BUT if my bass topped over $700 in value (and I know yours does hehe), I'd just take it to a repair shop. Its true what they say, you could probably end up wasting $10 but you could also end up wasting alot of time and energy. If you wanna learn how to solder and how to mess around with bass electronics, jump on craigslist (if it even works for you in germany lol :-D) and get yourself a cheap bass on there for you to mess around with. Most on there run from like $50 (Carlo Robelli ones) to a $300 (some Yamahas and Ibanez).

I know what I know about basses because I had two squiers p-basses so if i screwed up one i just took parts from the other and replaced it. It went like that for two years till i got my OLP MM3 and then finally my Spector NS2002B. Then I turned the Squier into a fretless and I STILL keep messing around with the electronics. I'm tellin ya, score yourself a cheap bass and just tinker with it. :-) Good Luck bro hope everything works out!

EDIT: I know some of what I stated isnt really a solution but I hope it helped to contribute to your final decision in someway!