Microphonic feedback

chrisjac2

Hi All,

Recently PUP's were removed and re fitted but now I have micro-phonic feedback on the neck pick up with hi gain. I've had a quick look and all looks to be wired up correctly,

The weird thing is the micro-phonic feedback goes when the tone down below 3? is that normal?

Can anyone point me in the right direction as to what I need to be looking for please.

Thanks

Funkfingers

It would help to narrow down the possible explanations by knowing;
1) what the host guitar is.
2) how the offending pickup is mounted into the guitar body.
3) whether anything about the pickup was changed while it was out of the guitar.

Remote diagnosis of wiring issues is usually aided by photographs.

chrisjac2

Funkfingers said:

It would help to narrow down the possible explanations by knowing;
1) what the host guitar is.
2) how the offending pickup is mounted into the guitar body.
3) whether anything about the pickup was changed while it was out of the guitar.

Remote diagnosis of wiring issues is usually aided by photographs.

ok, Its a Gibson Les Paul and is mounted in the usual manner, The pick up is an oil city Beano. its a 4 wire with the middle 2 soldered together as im not using the coil tap. They were popped out of the guitar as it was having some cosmetic work done so should have been a simple in and out.

Ill try to get a pic but I have been having issues trying to get them up on the forum lately 

chrisjac2

Funkfingers

If the OCP Bean-O humbucker is covered and not double wax-potted, microphonic squeal through high gain amplification is a “historically accurate” artefact, successfully replicated from the original Gibson design. 

Looking at your control cavity photograph, there are green and white conductor wires paired together, very near the Neck PU volume pot. It may be a line of sight effect but bare strands from one or other of these wires appear to be soldered to the chassis of the Neck PU volume pot. This would not explain microphony but it might create other noise problems.

In the OCP schematic diagrams that I have seen, red is hot/output, white/green are the series link (and, hence, coil split), black and bare get grounded.

chrisjac2

@Funkfingers ok thanks for your help, I never really noticed it before but I guess im confused as to why it only happens with the neck pick up and not the bridge?

Funkfingers

I cannot comment on your bridge/Treble position pickup without knowing what it is.

chrisjac2

sorry its the same Bean O as well

chrisjac2

@Funkfingers i resoldered the ground and it improved a bit thanks for your help

p90fool

Funkfingers said:

In the OCP schematic diagrams that I have seen, red is hot/output, white/green are the series link (and, hence, coil split), black and bare get grounded.

Take that with a pinch of salt, I ordered a matching pair of Oil City pickups and they were both wired differently. 
That took a bit of figuring out, I can tell you!