Help! Wiring did not work

[Martin Lang]

I just wired up my ST-1 build, plugged in and... nothing.

My ST-1 kit came with three wires to solder in: all of them attached to the volume (not two attached to the tone as per the PitBull wiring diagram - see attached image#1).



The wire attached to the lug is yellow, and the two wires attached to the top of the volume are both black.

Following the wiring diagram (and various YouTube videos), I see that the yellow wire is the "'hot' wire to tip" and the two back wires are both earths. Accordingly, I wired the yellow "hot" wire to the tip on the input and one of the black wires to the earth lug (see attached image #2).



In accordance with this advice (see attached image #3)


Then I soldered the other black wire to the bridge.

I double checked the wiring. I re-soldered the wires to check there was a good contact. Every time I opened up the jack cavity the wires were still attached.

I'm out of ideas. Any help appreciated
Martin

[Simon Barden]

It’s normally because you’ve got a signal contact touching the grounded shielding. Don’t fit the jack plate to the guitar but plug in a lead and see if you get any sound. Or it may be something in the main control cavity. There’s not a lot of a gap between the selector switch and the bottom of the cavity. Always a good idea to put some insulating tape on the shielding in areas where there may be contact with signal wire connections.

[Simon Barden]

It’s actually not that easy to get a Strat jack socket fixed in place with everything working. Especially if the body is a bit thinner than a USA one (as many Squiers and Asian-made Strat-style guitars are. Even on US guitars it’s not easy, and I’ve probably wired over 50 Strat sockets in my time. It’s the one piece of the design of the Strat that I think Leo didn’t do very well. The jack plate needs to be a bit longer with the socket at a shallower angle to the top.

[Martin Lang]

Thanks for that Simon - really clear.

I tried plugging in with the jack plate hanging off and... it works! I'll play about with some insulating tape and see if I can get it to work screwed in.

Cheers
Martin

[Simon Barden]

It's normally something simple, and it's happened to me in the past.

Glad it's nothing major.

[McCreed]

Good to see Simon got you on the right track.

FWIW, I typically don't put any shielding tape in the jack cavities of strats or teles. IMO the benefit is negligible and the chance of having a short are increased. I'll also point out that applying the copper tape to the metal jack plate is unnecessary as the plate itself is conductive.

There are alternative ways of dealing with an unshielded jack cavity, such as using coaxial cable as the output leads from the pots/switch to the jack, or twisting the positive and negative wire together in a helix fashion then applying heat shrink tubing over the pair (literally creating a twisted pair).

[Martin Lang]

It worked. At first it kept shorting out when I pushed the jack plate into position. Then I realised the tip of the lead was touching the copper shielding tape at the back of the cavity (I put some insulation tape at the back and this solved the problem.

So, I see your point McCreed about not shielding the jack cavity. I also see your point about not shielding the underside of the jack plate. I didn't really think about this, but as it's painted black I guess it might be insulated (a little?).

I don't really get your comment about alternative ways to deal with an unshielded jack cavity - but I don't have because it all works now! Very happy.
Martin

[Simon Barden]

If it's black hardware, then copper tape is the right thing to do on the jack plate.

Twisting the wires together makes thins neat within the main control cavity, but makes very little difference on an unbalanced signal cable. And by the time the wires come out into the jack cavity on a Strat, you'll want them separated anyway to get to the two jack tabs to solder.

Twisted wires are great if you are using a balanced signal with differential inputs (as on an XLR mic input on a mixer or an audio interface), but does very little for unbalanced signals. There is the argument that by twisting, the ground wire will pick up some of the RFI because it will sometimes be in front of the signal wire and absorb the noise, but it's almost negligible. I ran this through Hugh Robjohns from Sound on Sound magazine (and an ex-technical department instructor at the BBC) and he said it wouldn't do anything.

A shielded cable is more effective, but with standard single coil pickups, the amount of hum picked up by a few cm of wire mostly running inside a shielded cavity is negligible to the amount picked up by the many hundreds of feet of mainly exposed wire in the pickup itself.

I've shielded jack cavities on Strats before, mainly for completeness than any expectation it will do anything, but I always add insulation tape over the top at any point where the jack could touch. Remember that when the jack plug is inserted, it will push the tip contact out and down further towards the base of the cavity., so what might be OK without a jack inserted, can often become an issue once it is.

[McCreed]

So, I see your point McCreed about not shielding the jack cavity. I also see your point about not shielding the underside of the jack plate. I didn't really think about this, but as it's painted black I guess it might be insulated (a little?).

Ah yes, I didn't notice it was black hardware, so good call on your part!

[McCreed]

Twisted wires are great if you are using a balanced signal with differential inputs (as on an XLR mic input on a mixer or an audio interface), but does very little for unbalanced signals. There is the argument that by twisting, the ground wire will pick up some of the RFI because it will sometimes be in front of the signal wire and absorb the noise, but it's almost negligible. I ran this through Hugh Robjohns from Sound on Sound magazine (and an ex-technical department instructor at the BBC) and he said it wouldn't do anything.

I don't have the technical knowledge to dispute or defend that. I only know that it was information given to me by someone I respect and does have the technical know-how. I know this is next comment is a slippery slope, but I have also read lots of posts in other forums that say it works or at least helps, even with an unbalanced signal. However I understand "reading it on the internet does not make it true".

I've shielded jack cavities on Strats before, mainly for completeness than any expectation it will do anything, but I always add insulation tape over the top at any point where the jack could touch. Remember that when the jack plug is inserted, it will push the tip contact out and down further towards the base of the cavity., so what might be OK without a jack inserted, can often become an issue once it is.

With strats I always position the jack in the plate so the long positive contact is facing the front/top of the guitar so it can't be pressed against any part of the cavity (shielded or not). I also use a lock washer (antivibration) and ensure it's good and tight so it won't rotate.