Wednesday, 1 April 2015

Electric Guitar Repair

Doing a spot of repair work for "The Amazing" Nick on his rather rock-tastic electric guitar - a B. C. Rich with double humbucker pickups. I didn't know anything about electric guitar circuits so I had to do a bit of reading up. Thankfully this was a sensibly built guitar with a couple of screw panels on the back for wiring and servicing.

Get yer panels off, I'll give yer a good servicin'

It was simple wiring inside so I traced it all out and got the following circuit. Lots of bits of mini coax connected to the shells of the potentiometers as a ground reference. This guitar has a double humbucker pickup so has a selection switch to choose which set of pickups is used.

Wiring diagram

No output from the jack socket when the strings were plucked so it was quickly narrowed down to a faulty volume pot wiper.

The offending article
  • B500k COR-TEK pot
  • Notionally 500k ohms logarithmic response
  • Solder terminals
  • 23.5mm diameter body, 11mm deep
  • 8.7mm diameter mounting shaft, 10mm long to bottom of collar
  • 6mm diameter splined spindle
The chaps at Axe Tec had some suitable replacement guitar pots at a very reasonable price so I ordered two with the intention of swapping out both pots. They arrived very promptly so thanks Axe Tec  :)

During a bit of research I discovered that there are different log potentiometer response curves. Every day is a school day. There was no indication of the response curve type for the replacements but since they aren't matched to each other and adjusted by ear then I decided not to worry about it. The volume pot was a B curve and the tone pot had a D curve.

Anyway, parts arrived, were duly fitted and now there is something on the jack socket output other than 50Hz hum.

Rock on.

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