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82daion
Member
Username: 82daion

Post Number: 99
Registered: 5-2005
Posted on Thursday, September 27, 2007 - 4:46 pm:   Edit Post

I've been having some extreme problems with HF noise from my Series I recently-no matter what I do with the humcancelling trimpots, I can't seem to rid myself of an incessant buzz that manifests itself when the filters are turned up, especially from the bridge pickup. Said pickup has a chunk of epoxy missing from one of the corners-could this have possibly compromised the shielding network?

I know that these are classic symptoms for the electronics upgrade, but I can't afford to do that at the moment. Are there any repairs (such as pickup and IC replacement) that I could do myself? I love the bass, but the buzz has rendered it unusable for most situations, as the tone with the filters turned down all the way is not suited for the music I'm playing.

Any help would be deeply appreciated.
mica
Moderator
Username: mica

Post Number: 4840
Registered: 6-2000
Posted on Thursday, September 27, 2007 - 5:29 pm:   Edit Post

A few dB reduction of HF noise can might be had if you add a 15Kohm resistor across the neck and bridge pickup input terminals on the PF-6B card. Use a 16Kohm for the humcanceller pickup input.

If epoxy doesn't do any of the shielding, so unless the copper Faraday cage around the pickup coil is compromised (you'd see expanded copper (like mesh) or copper tape), what you describe wouldn't cause any hum problem.

The problem can be the pickups themselves. You can send your single coils in for testing to see if they match really well. If they don't, replacing these and using a 20Kohm trimpot across the humcanceller pickup input on the PF-6B board to get it to more closely match will help a few dB as well.

If it's truly hum (60Hz), then the humcancelling procedure should eliminate it.
82daion
Member
Username: 82daion

Post Number: 100
Registered: 5-2005
Posted on Thursday, September 27, 2007 - 8:16 pm:   Edit Post

This sounds good-I might have to wait on any pickup testing/changes for a while due to being short on cash, but just for kicks, what's the going rate on a set of SC-1s?

The Faraday cage of the bridge pickup is not compromised.

Where on the pickup terminals would I add the various resistors?

Thanks for your prompt and helpful response.

Chris
811952
Senior Member
Username: 811952

Post Number: 1151
Registered: 10-2003
Posted on Friday, September 28, 2007 - 9:47 am:   Edit Post

Chris,

If we can work out a place to meet in Indianapolis (I'd like to avoid GC this time if possible), I'd be more than willing to bring my bass so we could see if a pickup-swap moves the problem or not.

John
82daion
Intermediate Member
Username: 82daion

Post Number: 102
Registered: 5-2005
Posted on Friday, September 28, 2007 - 10:35 am:   Edit Post

John,

That sounds like a good idea, but I don't know if our pickups are compatible-mine have the mini-coax connectors, and I don't know if they'd work with the electronics in 811952.

Chris
811952
Senior Member
Username: 811952

Post Number: 1152
Registered: 10-2003
Posted on Friday, September 28, 2007 - 1:01 pm:   Edit Post

Ah, yes. Mine have the newer connector. Good catch. :-(

John
82daion
Intermediate Member
Username: 82daion

Post Number: 104
Registered: 5-2005
Posted on Saturday, September 29, 2007 - 10:11 am:   Edit Post



For a more visual representation, should I solder one end of the resistor to the neck pickup terminal and one end to the bridge terminal? The resistor should be attached to the pins from the pickup connectors and not to the traces on the circuit board, correct? Where does the resistor for the humcanceller need to go?

Thanks again for your help.

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