Bizarre pots crackling problem - now solved !

[hamfist]

Over the last few days I've been suffering from a very annoying "crackling pot" on one of the pickups on my G&L SB-2 bass. No probs I thought, I'd changed the pots recently so it must be a dodgy solder joint.
So, in I go, re-do all the joints .... no better.

OK, must be the pot, thinks me, Brand new CTS pot is duly installed. With a smug look on my face I test it out, only to discover that this damned crackling sound is still there on the bridge pickup only. I seemed to get about 20 seconds of playing with no crackling and then it would quickly get worse until it was unuseable on that pickup.
Neck pickup and sound behaves perfectly.

What would you're next move have been ?

Anyway, in frustration I have a very close close look at everything and I then notice a tiny, tiny strand of fluff that is just bridging the gap from the pickup to the G string. When I started playing it wasn't touching, but after a few seconds, a static charge builds up between the pickup and the string attracting the strand of fluff towards the string. Whenever it touched the string it gave an electrical connection between the string and pickup and caused a crackle. It's definitely a first for me.

So anyway a good clean and a slight lowering of the pickup, to reduce the chances of it happening again, has sorted it out. Just thought I'd post it here as I'd never come across that problem before.

[charic]

Wow... the odds on that happening are pretty slim

[V4lve]

Interesting. I have an ongoing pot crackle thing that I had learned to live with but has started to bother me again. I isolated it this morning. If I play a few notes and then fiddle with the pots they crackle. If I then give the strings a good wipe up and down the neck a few times with the same hand and then fiddle with the pots they don't crackle. It's repeatable. There is a ton of shielding in the cavity and under the cover and everything seems earthed (to my limited knowledge). Is there anything else I can do to get rid? Ta

[hamfist]

[quote name='V4lve' timestamp='1363258643' post='2010502']
Interesting. I have an ongoing pot crackle thing that I had learned to live with but has started to bother me again. I isolated it this morning. If I play a few notes and then fiddle with the pots they crackle. If I then give the strings a good wipe up and down the neck a few times with the same hand and then fiddle with the pots they don't crackle. It's repeatable. There is a ton of shielding in the cavity and under the cover and everything seems earthed (to my limited knowledge). Is there anything else I can do to get rid? Ta
[/quote]

I'm guessing you've now put your glasses on and checked for rogue fine bits of fluff that might be grounding out the pickup to the string ?

[V4lve]

I took the cover off and fiddled with wiring and boards. The main pre-amp board make a lot of noise when I run my finger across the back of it. Should that happen?

[icastle]

[quote name='V4lve' timestamp='1363335206' post='2011604']
I took the cover off and fiddled with wiring and boards. The main pre-amp board make a lot of noise when I run my finger across the back of it. Should that happen?
[/quote]

Very likely.

Best bet with any sort of fault diagnosis is to eliminate the obvious things first.

Get a can of switch cleaner and clean the pots.

[V4lve]

Tried switch cleaner, earthing, shielding and even dryer sheets. Beginning to wonder if it is the pick guard.

[icastle]

Is it a plastic pickguard?

[V4lve]

Might be. It's a cheap bass. How do I tell?

[icastle]

[quote name='V4lve' timestamp='1363374508' post='2012129']
Might be. It's a cheap bass. How do I tell?
[/quote]

That's got me stumped, I've never been asked anything like that before...

What colour is it?

[V4lve]

Brown tort kind of colour. It's an OLP.

[icastle]

Well that's plastic, so it's not that - you can't earth plastic.

Next thing to check would be the soldering.

You're looking for dull solder joints.

While you've got the control cavity open, plug the bass in (keep the volume low) and poke around the wiring to see if anything you prod makes the crackling appear or disappear.

Move the wiring about gently to see if one of the cables has got a fracture inside it.

[V4lve]

Ok.I wiggled all the wires and checked the solder. All seemed OK apart the plugs on the board. I cleaned them but no difference. But did notice that the static crackle goes away when the guard is away from the bass.

[rmorris]

[quote name='icastle' timestamp='1363478357' post='2013297']
Well that's plastic, so it's not that - you can't earth plastic.
[/quote]

Woahh...it can def be caused by a 'plastic' pickguard. It seems that when they get worn they can generate 'staic' type inteference when touched / rubbed. Plenty of info if you Google it.
Look for 'shiny' bits on the pickguard where it's been 'polished' by hand movements etc.
I had this happen on an Ibanez Strat copy. You can shield with foil and dryer sheets also work to a degree ( they are 'anti static' )- but I got a new pickguard cut at a place in Orpington.

[BILL POSTERS]

[quote name='rmorris' timestamp='1363652647' post='2015459']
[b]had this happen on an Ibanez Strat copy.[/b]n shield with foil and dryer sheets also work to a degree ( they are 'anti static' )- but I got a new pickguard cut at a place in Orpington.
[/quote]

Matter of interest, was it a 3 ply one ? Just wondering if it had a different material in the centre.

V4LVE,
Are the pot casings both connected to the outer terminal on the jack.ie, earthed ? and are either oof them loose ?

[V4lve]

[quote name='BILL POSTERS' timestamp='1363653617' post='2015468']


Matter of interest, was it a 3 ply one ? Just wondering if it had a different material in the centre.

V4LVE,
Are the pot casings both connected to the outer terminal on the jack.ie, earthed ? and are either oof them loose ?
[/quote]

Pots appear to be earthed.

[V4lve]

[quote name='rmorris' timestamp='1363652647' post='2015459']


Woahh...it can def be caused by a 'plastic' pickguard. It seems that when they get worn they can generate 'staic' type inteference when touched / rubbed. Plenty of info if you Google it.
Look for 'shiny' bits on the pickguard where it's been 'polished' by hand movements etc.
I had this happen on an Ibanez Strat copy. You can shield with foil and dryer sheets also work to a degree ( they are 'anti static' )- but I got a new pickguard cut at a place in Orpington.
[/quote]

I think I might get a replacement guard to see what happens.

[icastle]

[quote name='rmorris' timestamp='1363652647' post='2015459']


Woahh...it can def be caused by a 'plastic' pickguard. It seems that when they get worn they can generate 'staic' type inteference when touched / rubbed. Plenty of info if you Google it.
Look for 'shiny' bits on the pickguard where it's been 'polished' by hand movements etc.
I had this happen on an Ibanez Strat copy. You can shield with foil and dryer sheets also work to a degree ( they are 'anti static' )- but I got a new pickguard cut at a place in Orpington.
[/quote]

I've heard of this but have never found myself hugely convinced.

You need the right mechanical interactions and humidity and to create and maintain a static charge on a material and I find it unlikely that many people manage to get both of these environmental anomalies on a regular basis.

Some materials are prone to static (ever been in an office where your shoes, the carpet surface and metal door handles give you a spark?) but finding the 'correct' combination of materials in a scratchplate would take an illogical degree of work.

Even if it *is* a static charge, once it's dissipated then it's not likely to reappear in a matter of seconds.

Shielding scratchplates and body cavities is more to do with eliminating RFI than controlling the build up of static.

I'm not doubting that changing your scratchplate resolved the problem you were having but I'm more inclined to think that the physical process of moving stuff about when you changed it actually rectified the original issue.

But hey, I'm no physicist so I'm quite happy to be wrong.

[BILL POSTERS]

Have you tried a different amp ?

Its possible, just possible that the coupling cap to the first stage is leaky and putting DC on to the pot sliders. Early death of pots, and crackly new ones due to leaky coupling caps wasnt uncommon back in the days of steam valve radios.

btw, plastic fuel tanks are supposed to be earthed to prevent static sparks igniting the fuel. Dunno how that works though.

Maybe a 3 ply scratchplate, with 2 plastic sheets insulated from each other by a different type of plastic, which would act as a dielectric, could build up a charge between the two. Or am I just talking complete bollox ?

[Paul S]

Title says 'now solved' - how, please?

[V4lve]

[quote name='Paul S' timestamp='1363774041' post='2017235']
Title says 'now solved' - how, please?
[/quote]
Sorry. I hijacked someone else thread. I guess I need to solve it quick.

[V4lve]

[quote name='BILL POSTERS' timestamp='1363715536' post='2016479']
Have you tried a different amp ?

Its possible, just possible that the coupling cap to the first stage is leaky and putting DC on to the pot sliders. Early death of pots, and crackly new ones due to leaky coupling caps wasnt uncommon back in the days of steam valve radios.

btw, plastic fuel tanks are supposed to be earthed to prevent static sparks igniting the fuel. Dunno how that works though.

Maybe a 3 ply scratchplate, with 2 plastic sheets insulated from each other by a different type of plastic, which would act as a dielectric, could build up a charge between the two. Or am I just talking complete bollox ?
[/quote]
It happens regardless of what I plug it into. In fact it seems to have infected one of my pedals too.

[rmorris]

[quote name='BILL POSTERS' timestamp='1363653617' post='2015468']
Matter of interest, was it a 3 ply one ? Just wondering if it had a different material in the centre.
[/quote]

It is a three ply Black/white/black. I'd assume material was the same ? but don't know.
I think it's only the outer surface which you touch that is the issue as it gets 'polished' over time where touched often including round the pots.
I recall finding quite a bit of discussion on it on the web if Googled. Seem to remember it was a particular point of discussion on a Telecaster forum.

[V4lve]

It's a three ply tortoiseshell guard. Might replace it with a temp home made jobby to see what happens.

[discreet]

[quote name='icastle' timestamp='1363712479' post='2016418']
I've heard of this but have never found myself hugely convinced.
[/quote]

'Tis true, our guitarist had this problem and it was indeed a build-up of static from his plastic pg. He shielded the back of the pg and connected it to earth and lo, all was silent thenceforth.

Edited March 20, 2013 by discreet