ST-1 body barely audible when testing pickups with magnetic screwdriver

[b0jang]

I thought I would try test my soldering/wiring before proceeding any further so I plugged the body into an amp and found I had to max out the volume on the guitar and amp before I heard a barely audible noise when tapping the pickup poles with a magnetic tip screwdriver. The good thing was the pickup switch seemed to correspond correctly to the right pickups. Also I'm using copper shielding in the cavities but maybe it's not grounded properly? I'm a bit clueless on the electronics side of things.

Is my method just flawed? I thought I would hear something much louder. I tried searching online and found a few posts about the poles being covered in plastic but they look metal to me. Will I be ok if I string it, or is there something I'm missing and should look at? Appreciate the help.

[Trevor Davies]

Hi b0jang.

I would expect a loudish sound if the volume is maxed out. I only use a battery powered amp for testing, but it is very audible on a small amp volume.

It is good that the switch and pups work appropriately. I would not think that it is the shielding not being grounded (since it would be noisy! Or if a hot wire was grounded on the shielding there would be no sound). It could be a poor solder (or dry joint).

Can you include a close-up photo of the wiring in the cavity? That will make it a bit easier to problem solve.

[b0jang]

Hey Trevor, here are some images. Hopefully it's clear, can upload more if needed.

[Trevor Davies]

For the jack socket, I think the black wire's solder joint looks a bit dry (i.e. it has not really soldered to tab). Maybe try heating the joint again until the solder runs to the metal on the tab. You should not need any more solder! Even the yellow wires connection could be heated a bit more.

Hopefully this will do it!

When I solder to the jack tabs I twist the wire strands around each other, feed that through the tab hole, and then twist it to wrap around the end of the tab. Some folks also solder (tin) the strands of the twisted wire before trying to solder to the tab.

[Trevor Davies]

Additional:

Also put some electrical tape around the tabs and the yellow and black wires of the jack socket. The tabs may be touching the shielding in the jack socket cavity.

[fender3x]

You should be able to hear a very clear, relatively loud sound when you touch a heavy metal object to the pickup. Make sure you're using something big enough. A small end-wrench (spanner?) is better than a screw driver. Something with some ferrous metal mass.

It sounds like it is either grounding out somewhere (as TD suggested) or you have a loose or cold-soldered connection (as TD also suggested). Starting with the jack is a good idea (...TD again...does it seem like a pattern is forming?).

One confusing thing (at least to me) about your wiring is that all the black leads seem to be grounded, and MOST of the yellows seem to be grounded as well. The exceptions seem to be the yellow lead from the bridge pickup, and yellow lead from the middle lug of the volume pot to the jack. Check the black wire solder joint at the jack. Also check it at the other end. From the pics I can't tell where the black wire ends. It should be grounded to the case of one of the pots.

If those connections are good, check the yellow wire's connections: To the middle lug of the V pot. the other end looks good, but checking won't hurt. Next the red wire's connection from the switch to the V pot's lug that is closest to the switch. If that's good, check all the casings of the pots and switch. All of them should have a good connection to the ring on the jack.

[fender3x]

It also occurs to me that you might consider stringing it to do your test. That's relatively easy to do with a Strat. It's hard with a semi hollow, so I built a jig to test the wiring harness on a bass.



Relatively easy to build from found objects at my house. The nice thing about doing something like this is that you can also test caps, try different pickup heights, different pots, etc.

Like all my jig's this one is ugly. Also not an original idea, but taken from pics I saw of Leo Fender's lab where he had jigs for testing pickup locations and heights, as well as wiring harnesses...

[Trevor Davies]

...
One confusing thing (at least to me) about your wiring is that all the black leads seem to be grounded, and MOST of the yellows seem to be grounded as well. The exceptions seem to be the yellow lead from the bridge pickup, and yellow lead from the middle lug of the volume pot to the jack. Check the black wire solder joint at the jack. Also check it at the other end. From the pics I can't tell where the black wire ends. It should be grounded to the case of one of the pots.
...

The ST kits are preloaded. So, the mixing of the coloured wires was done in the factory. It is quite frustrating. The factory could at least pick a common ground colour.

[fender3x]

The ST kits are preloaded. So, the mixing of the coloured wires was done in the factory. It is quite frustrating. The factory could at least pick a common ground colour.

It makes no sense to me that the two leads that run to the jack are both colors used as grounds.

I think the advice about re-soldering the leads at the jack is good. Also the black tape. If that does not work, I am guessing the problem is here somewhere at the V pot:



What it should look like is that the upper lug should have the red wire from the middle of the jack and nothing else.
The middle lug should have only the yellow wire going to the jack attached.
The bottom lug should be soldered to the case along with the black wire to the jack, the black wire to the bridge and a yellow ground wire from the 1st T pot.

The only other place that looks like it might be the culprit for a short is that star ground at the 1st T pot, since it grounds all the pickups.

[b0jang]

Thanks all, will give it a go this weekend.

fender3x - this is where I was getting confused actually, in the wiring diagram it's got wires coming off the bottom tone pot - however in my case every wire that I needed to solder came off the volume pot. I'm a little clueless on electronics so I assumed that it didn't matter as long as it was connected to some pot.

So in regards to the picture of the volume pot you've posted, the first lug (reading from left to right) has a red wire going from it to the 5 way switch. The second lug has a yellow wire going from it to the output jack, and the third lug has been bent upwards on to the volume pot and has 3 wires soldered on to it - a yellow that goes to the adjacent tone pot, and two black wires which I have soldered to the bridge and output jack. Let me know if that sounds off.

Here's a slightly better picture and one of the back: