Grounding question - P-Retro hum - sorted!

[Paul S]

Help!

I've just fitted a P-Retro into my P- Bass but despite shielding all the cavities with copper foil I am getting a hum that gets MUCH worse when I touch the controls or the pup magnets. Usually, when I get a humming it stops when I touch the strings, but this time these are fine!

Evidently I need to look at something but I don't know where to start for such a specific hum - any suggestions?

Ta!

Paul

Incidentally, I have fitted P-retro to two other basses and a J. East to a Precision Lyte - but this is the first time in a proper P. Bass. Wizard Trad pup. Just WOW.

Edited December 29, 2012 by Paul S

[deepbass5]

If you have just fitted it and you are at home. not out on a gig. do you have a dimmer in your room. I had the same thing happen and it was my 4 gang house dimmer. worth checking and cleaning the earth under the bridge. clean the wire solder the end and reposition it under the bridge, I have also filed black bridges down to the brass if required.

good luck

[GreeneKing]

It may be worth checking that all the shielded cavities are connected. Give John East an email. He is very helpful. If you link out the pup and it goes its a shielding issue. I used conductive paint and found it as effective but much easier than foil.

[dave_bass5]

Paul, i had exactly the same issue with the pole pieces with my P-Retro. It didnt seem to matter if the bass was in active or passive mode, touching the pole pieces gave me a loud hum. Even using a wireless system at gigs (im not sure if thats actually relevant though). As i play with a pick it wasnt really a big deal, but i did find it annoying that it could happen.

I didnt have any issues with touching any other part of the bass though, not even the knobs.

One thing to watch out for is that none of the lugs on the input jack is touching the cavity walls. My Squier CV is shielded with paint and i did have volume issues when i first put the P-Retro in, and it was down to one of the lugs touching the wall. Also make sure the small brass spring is making contact in the pots.
Im not sure if that helps, just passing on my experience. It sounds like you know what you are doing.

For what its worth i spoke to John and he seemed to think its normal for this type of pup, but ive never had it before, and after taking the P-Retro out and putting the old stuff back in there is no pole piece hum at all.

[Paul S]

Thanks for your suggestions.

Deepbass - no dimmers here. I've made a good earth on the bridge, ramming down the wire into a screw hole, so I don't think the bridge is the problem.

GreeneKing - what do you mean when you say 'link out the pup'?

Dave - Sadly I have no idea what I am doing! I can read intructions and carry them out but if it doesn't go to plan I am pretty well stumped. Yes, makes no difference active or passive. I checked the lugs in case it was that and it wasn't. It seems to me that something in the unit wants to be earthed but I don't know where to start.

Trying not to pester Mr East but may have to.

[pete.young]

[quote name='dave_bass5' timestamp='1356791868' post='1913653']
Paul, i had exactly the same issue with the pole pieces with my P-Retro. It didnt seem to matter if the bass was in active or passive mode, touching the pole pieces gave me a loud hum. Even using a wireless system at gigs (im not sure if thats actually relevant though). As i play with a pick it wasnt really a big deal, but i did find it annoying that it could happen.


[/quote]

That same P-Retro is now in my japanese Precision . There's no hum, even if you touch the pole pieces. However there is a hum when you touch the active circuit knobs.

[dave_bass5]

Well at least you had better luck with it than i did Pete. Make sure those springs are making good contact. I was very surprised that i didnt have that problem.

Funny how the three of us have got different results. Just goes to show there is more to this lark than it first seems.

Paul. Can you keep us updated with this issue. I'd love to know whats causing it, especially the pole piece issue.

Good luck.

[GreeneKing]

What I meant is what John suggested for checking my noisy U Retro'd Jazz. Disconnect the pup and replace with a wire link in the terminals. If the hum goes its a shielding issue.

Peter

[Paul S]

Okay.

Picking up on Dave's suggestion, I soldered a wire to the pickup cavity tape and also a wire to the control cavity tape. I'd never done this before but it worked surisingly well. Well, I was surprised. I bundled these with the earth wire from the bridge and soldered them to single wire which went into the relevant connector on the unit.

Result - no hum.

Or, at least, as little as makes no difference - with the tone control rolled off a fraction it isn't noticable. Well, not to me - but my ears are shagged anyway!

Fitting all those extra wires inside the cavity is a bit of a squeeze but nothing dislodged in the process.

Yeehah!

Edit - just saw your reply while I was doing mine - thanks for that.

Edited December 29, 2012 by Paul S