I recently purchased the GPR-1, which features 2 4-conductor humbuckers, 1 volume, 1 tone, 1 3-way toggle and 2 switches for coil splitting. Most of the wiring is already done, but I can't seem to figure out how to wire the humbuckers to the switches. There is no diagram for this and I've scoured the Internet with now luck. Does anyone have a diagram for this??
Are the switches really single pole double throw switches? For straight coil tapping you'd expect single pole (or double pole) single throw (two position) switches. If it's a double pole double throw switch (three position) you can use it for coil splitting and series or parallel operation of each humbucker.
OK, if it is just like that switch and is an ON/ON you can use it to split the humbuckers.
The humbuckers should have four coloured wires and a braided screen. One of the wires will be soldered to the braided screen, two more wires will be twisted and soldered together and probably have some heatshrink over the end, and there should be one wire on its own.
That single wire is the signal hot wire, and would go off to the selector switch.
The screen+single wire is connected to ground, normally on the back of a pot but you can use the common ground lug on the switch if it's more convenient.
The two other joined wires with the (hopefully) insulated end need the insulation taking off and both those wires you'd solder to the central lug of the switch. You'd run a ground wire to one of the other lugs on the switch run from the back of a pot. This ground wire can be run on to the other switch if you want, or you can run a separate ground wire if that's easier. The switch is reversible, so it depends on which way round you physically install it as to what will be humbucker mode or what will be coil split mode. The switch position for the coil split will be the opposite end of the switch to the lug with the ground connection.
You may need to take some of the overall cable insulation off and unwrap some of the screen to get the wires long enough to stretch to the selector switch and the coil tap switch. Alternatively you could join a longer single coil wire to the insulated two-wire joint connection (I'd put heat shrink over this to stop accidental grounding and for some extra mechanical strength) and then run that to the central mini-switch lug. This is preferable if you want to build a wiring harness that runs around the outside of the lower F-hole so it's not visible. Make up a cardboard template with the pot holes, and switch holes marked on and holes made, and draw the F-hole location, Fit the pots and switches and wire up as much as you can (so all except the pickup connections. Run your wires around the hole location. You can tape wires together for more overall rigidity and help them not flop loose.
Don't forget that if you draw on the cardboard from the top (I usually use paper first to trace the pot positions then stick that to the card before poking holes), then you then need to flip it over as you'll be fitting the pots and switches from the underside of the guitar top, so everything is reversed.
Last edited by Simon Barden; 06-05-2021 at 07:15 PM.
GPR-1 Wiring with SPDT switches
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