Thanks Simon!! No dimmers or fluorescents nearby. Tried it into two amps. A ‘66 fender Vibrolux and a Roland Cube. Both had the him and both are properly grounded three-pronged plugs.
Here are the pics of the pots and switches. The pic in links above shows the whole harness
OK, there are definitely some wiring errors. Just about bedtime for me here, so I'll have a more detailed look in the morning (though others may chip-in before then, but the master tone pot shouldn't have the black wire from the back of the pot to the third (top) lug of the pot. Remove it completely. The capacitor should be connected to the lug the black wire is connected to for the tone control to work the correct way round. The wiring diagrams are shown looking at the back of the pots (i.e. from the rear of the guitar to the front), not as if looking down from the top of the guitar towards the rear.
It shouldn't be causing the hum, but it will explain the tone knob's effect on the hum. With the pot at either end of it's travel, the signal is currently fully grounded one way and grounded through the capacitor (so only low frequencies pass through as a tone control turned fully down should). In the middle, some of the buzzy signal is being grounded, so the output will be quieter than it should, with the rest going to the nice amp.
Shorten the leg of the capacitor that's going to a pot lug so that it can't be accidentally bent when inserted into the guitar and touch the pot casing and so ground the signal. Or get some heat shrink and put it over that leg to insulate it. You might as well shorten the or insulate the other leg to, just to be sure it too can't get bent and short out something.
Tone pots work as variable resistors so only have two of the lugs connected.
Volume pots work as 'potential dividers' so normally have the two outer lugs connected across the signal whose volume is to be controlled, with the output signal connected to the middle lug, the 'wiper', the arm that sweeps around the potentiometer's carbon track.
Ahh. I am an idiot. I think I see what I did. The diagram from pit bull page for the GR-1SF…Since the pickups in the picture are facing up (and the pots are in the same places as when viewed from front of the guitar) I thought you had to flip the pots and switches right side up and then the leads would be in different order. So…basically I have to view the number of the pot leads as if I was looking down from the top. So I mistakingly my made all my first leads my third leads! Right? Just switch all my 1’s and 3’s. I will have to rewire all those flips
My pot leads are not long enough to bend back to touch the pots so those short black wires are there to just jump to ground to the pots (of course, from my mistake above) they are all on wrong side now). And I see that the third lead on the master tone pot does NOT need the ground back to the pot.
Can’t thank you enough for taking the time.
Last edited by DIEFOX1; 10-01-2022 at 09:06 AM.
On the soldering, you’re not really getting the back of the pot hot enough to properly melt the solder. As a result it’s all ‘blobby’ and sitting rough and proud of the surface. It should have a rounded smooth, shiny surface to it.
I don't know what size iron you have. An 18W-20W iron is fine for small electronic components, but you really need a 50W-60W iron for soldering to the rear of pots, and ideally temperature controlled and with a fairly large tip that has some heat storage capacity so it doesn't immediately cool down when you touch the back of the pot.
From the resistance measurements, it seems there's enough contact for the moment, but you are fairly close to having a few dry joints, and these rough solder blobs can allow oxidation to creep under them over time.
It helps if you apply solder ('tin') to the back of the pot and the wires first, before putting them together and heating them up. Solder will stick to solder more easily than solder to the metal, so it just makes life that bit easier.
Here's a drawing to help with the pot soldering lugs:
The 1 - 2 - 3 order shown is a widely accepted method of numbering.
Making the world a better place; one guitar at a time...
I have a Matt Guitar Murphy sig, that came from the factory with a bad solder joint on the back of the pot. I used a dremel tool with a little sanding disc to rough a small spot on the surface that I was soldering to. It worked great. I DID use a soldering gun with a fairly heavy tip, like Simon recommended. Transferred enough heat to do the job in a few seconds.
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Thanks for all the responses again! Now that I understand the wiring diagram better, I will pull out the big dog soldering iron with a bigger tip and clean up those grounds when I fix the order of the leads. I was a little afraid to apply too much heat to the back of the pot as I was afraid of damaging some internals. The dremel tool suggestion sounds good as well.
Counter-intuitively, a bigger iron is better for soldering the pack of pots with less risk of heat damage. With a smaller iron, you need to keep the iron on for much longer to get the top hot enough; allowing all the pot to heat up.
A bigger iron heats up the local area quickly (should be a couple of seconds at most), so the main heat stays fairly local. As long as you get the solder and wire on there ASAP, it will be fine. The heat will then dissipate to the rest of the pot, but it won't get as warm as if warmed for a long time. Using metal mole grips/self-clamping grips on the sides of the pots helps absorb some of the excess heat and reduces the risk of damage.
I had high hopes with the suggestions offered above but still have a hum - though lower in volume it is still there. New problem is neck pickup doesn't work. I have attached pics of the new wiring harness and a (prob easier to read) schematic of the connections.
One thing - some of the wires I was using for longer runs were braided metal wires - thought they would be better at shielding. I now realize the outer braids of these wires should be grounded to pots as well right?
Any other suggestions before i rip it all out and start again???
Here is written description of wire connections:
Switch 1 to Neck Vol 3
Switch 2 to Master Vol 3
Switch 3 to Bridge Vol 3
Switch 4 to Master Vol Pot Ground
Switch 4 to Master Tone Pot Ground
Master Volume 1 to Pot Ground
Neck Volume 1 to Pot Ground
Bridge Volume 1 to Pot Ground
Master Vol 2 to Master Tone 2
Master Tone 2 to Input Tip
Neck Pickup Red/White taped to nowhere
Neck Pickup Green/Bare to Ground Neck Vol
Neck Pickup Black to Neck Vol 2
BRIDGE Pickup Red/White taped to nowhere
BRIDGE Pickup Green/Bare to Ground BRIDGE Vol
BRIDGE Pickup Black to BRIDGE Vol 2
Master Vol Ground to Neck Vol Ground
Neck Vol Ground to Bridge Volume Ground
Bridge Vol Ground to Input Sleeve
Bridge Vol Ground to wire ground for bridge
Last edited by DIEFOX1; 13-01-2022 at 06:30 PM.
No pics. My only comment is "yes" on the metal braid being grounded.
Making the world a better place; one guitar at a time...
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