Wiring diagram for 2 p90 pickups

Dr_Necessiter

Dear Fretboarders,

My first stupid question of 2023: I'm looking to fit 2 p90 pickups, 1x volume and 1x tone pots and a 3 way toggle switch to my guitar. This diagram from Tonerider (hope I can say that here) would seem to fit the bill.

https://tonerider.com/wp-content/uploads/2020/03/WD_PP_11T.pdf

The part I'm a bit vague on is where the various earth connections are made. I've seen other diagrams where everything is earthed via the volume pot, including the tone pot and wondered if that approach was viable in this case? Apologies if this is blindingly obvious but I'm new to guitar electrics (and electrickery in general) and would be grateful for any comments.

Kind regards,

Dr N.

downbytheriver

Yes, if you attach every earth to the back of the vol pot then all will be well. Odd way of drawing it though. 

Dr_Necessiter

Thank you!

ICBM

If it’s easier - soldering to the back of a pot can be tricky, without a powerful iron and the right technique - then you can do it exactly as shown and use a separate terminal to attach all the grounds to. If the guitar has shielding foil in the control cavity then a terminal screwed through it and into the wood also provides the connection to the shielding.

BillDL

The last time I wired a guitar I decided to use the method outlined in THIS VIDEO as my terminal for all ground wires at the volume pot.  I used a leftover bit of leg from a capacitor as the connection wire between the volume pot solder lug and the back of the pot and soldered all the wire ends to that.  Nice and neat and not any more fiddly than soldering all wires to the back of a pot or to a common terminal in the cavity.

Jonathangus

@BillDL - that link goes to a main channel page, not a specific video.

Dr_Necessiter

I found the vid - thanks to everyone for the replies and the tips. 

Jonathangus

Ah, this one, I think:

Funkfingers

For a two pot circuit, with single conductor + braid pickup output cables, the easiest approach is to ground the pickup braids to the selector switch chassis. 

Thereafter, the ground path is the shielding wire(s) in the cable run between the selector switch and volume pot.

The Tonerider schematic diagram follows the industry convention of not specifying exactly where ground connections are made.

The drawing also represents the notion of the connections to be made rather than the actual physical layout. e.g. The pickup cables need to arrive at the selector switch from the grounding lug end.

Pull back the braid far enough to expose an inch or so of the inner conductor. Solder the braid(s) to the selector switch ground lug. You should have enough of the inner conductors available to connect to their respective leaf terminals. This way minimises cable strain and prevents shorting out.

BillDL

Thanks for that @Jonathangus.

Dr_Necessiter

Thanks again to everyone for the replies. I'm waiting for the pots etc to arrive and once they land and I've connected stuff up I'll let you know how I got on.

Sporky

Pots and switches aren't designed to have things soldered to their casings. Much easier and better to have a loop of uncoated solid core wire attached to a screw in the cavity somewhere, and earth everything to that one point.

No need for a monster iron and no risk of melting any of the innards. 

Dr_Necessiter

Dr_Necessiter said:

Thanks again to everyone for the replies. I'm waiting for the pots etc to arrive and once they land and I've connected stuff up I'll let you know how I got on.

So the answer is not very well - I have a dead guitar. I'm hoping that there's something blindingly, stupidly obvious that I've done/ not done (repeatedly) that means that I haven't got past first base because I've had three goes at assembling the bits now with not the faintest squeak from the guitar. What I've done:

• Tested all of the components with a multimeter before assembling, all appear to be working OK;
• Tested each soldered joint as I made it to confirm no bad connection - all apparently good;
• Followed the advice in Bill's video about earthing to a wire soldered to the volume pot - the bridge, jack and tone pot are earthed to this;
• The pickups are earthed to the volume pot directly (sorry Sporky); and
• The toggle switch earth is wired to the pickup braids (sorry Funkfingers).

I've re-tested all of the components to check that they're still alive, re-checked the soldered connections for continuity and tested the earth between the bridge and the output jack again with the Ohm function on the multimeter and nothing comes back OL. I'll post some photographs once I get some daylight but any help gratefully received.

SteveRobinson

Have you attached to earth and output wires to the correct ends of the switch? 

I have seen this done the wrong way round, as switches can be constructed differently which can cause confusion.

ICBM

Or you may have a short - that will give continuity readings but no sound (dead silence, not even background noise).

If you plug the guitar into the amp, set the volume control to halfway, and touch the middle terminal of the pot, does it buzz through the amp? If no, the jack or its wiring are probably shorted. If it does buzz, but touching the input terminal of the volume doesn’t, then there’s probably a short at the switch or tone pot.

Dr_Necessiter

Hi Steve, 

Many thanks for the reply - I did make that error in one of the earlier goes but cured it.

Anyhow it now lives: had another check over in the cold light of day and the wire that I soldered from the earth on the volume pot to the pot casing wasn't properly fixed at the casing end. It wasn't obvious visually and I assume there was enough of a connection for the multimeter to give me a positive reading. Anyway, re-soldered it, plugged in and bingo!

Thanks once again to everyone for their advice and it has been a good learning experience. Now to go make some noise!

BillDL

Good job Dr_Necessiter.  It's quite disheartening when you spend ages getting everything right and double checking only to find it doesn't work.  Your discovery was that "the wire that I soldered from the earth on the volume pot to the pot casing wasn't properly fixed at the casing end".  It can be pretty hard to get a good solder joint to the back of a pot casing.  If the soldering iron isn't powerful and hot enough you end up with the tip on the casing too long trying to melt the solder and the result can often be a dodgy joint, and if the iron is a powerful one you risk damaging the insides unless you are quite well practiced and can get the iron on and off quite quickly.  Scratching the metal with rough sandpaper and wiping it with solvent can help with the solder joint, but it still needs quite a hot iron.

The majority of people just bend the solder lug on the volume pot back until it is touching or almost touching the case and join it to the case with a blob of solder.  The method you used from the video I linked to still needs a wire soldered from the solder lug of the pot to the case, but it is thereafter easier, neater, and requires less heat applied to the case when you are connecting the other ground wires to that single wire rather than joining all the wires to one large blob or separately to multiple blobs of solder on the pot casing.  Different people have their own methods, but I like the method you chose to use.

ICBM

BillDL said:

The majority of people just bend the solder lug on the volume pot back until it is touching or almost touching the case and join it to the case with a blob of solder.

This method is prone to stressing the rivetted connection from the ground terminal onto the track board if you're not careful to only bend the upper part of the terminal with pliers, which leads to the pot not turning fully off because some resistance has been introduced (in the worst case the pot barely turns down at all). You can usually fix it if you squeeze the rivet hard onto the track board with a pair of fine-nose pliers, but using a wire eliminates the problem in the first place.