Tuesday, 30 September 2014

Converting Shielded Pickups for Phase Switching

I was going to write a massively complicated post about all the wiring options for three pickups and the rig that I have made for testing out the different sounds, but that is going to have to wait because I have realised I have a problem with the Vanson P90 pickups.

One of the things that I want to do with the pickups is to switch the phase. There is nothing complicated about phase switching, you just switch the positive and the earth wire on one pickup and then it will be out of phase relative to the others.When pickups are out of phase they tend to be a little quieter and have less bass.

The only problem is that the earth wire on the Vanson P90s is connected to the metal case. When wired in phase, the case reduces electromagnetic hum. When wired out of phase it does the opposite and acts like an antenna.

The only way to fix this is to replace the two wires with three. One for each end of the pickup coil and the  other connected to the case so that the case can be grounded independently of the pickup wires.

The pickup cover is connected to the base of the pickup with a couple of blobs of solder. My soldering iron was not hot enough to melt the solder so I used a craft knife to carefully cut through the solder so I could get inside the pickup.

I was surprised to see that the pickup wasn't much bigger than a strat pickup inside the cover, I was expecting something a little fatter. You can see that there are two wires coming out of the pickup. The black wire is soldered to the case and the cable shield. The white wire is connected to the cable core.

I cut the wires off, leaving myself a little slack and attached a two core shielded cable. The shield wire I connected to the pickup base. It was a challenge to solder it it because the base sucks the heat out of the soldering iron. In the end I laid the cable in the gutter between the edge of the base and the magnets and then laid some solder on top of it. When I melted the solder it solidified almost immediately the heat was off and held the wire in place

For the other wires, I cut a short length of shrink wrap and slid it on. Then I twisted the ends of the wires together (black to blue, white to red) and applied a little solder. After the solder cooled I slid the shrink wrap over the joint and applied some heat with the iron.

I re-assembled the case and applied a bit of solder to stick it back together.

So far so good. I just have two more to do and then I can get on with the rest of the wiring.