new harness install noise

[Randall]

I just put in a new Gibson ES 335 50's style harness from 920D Custom in a Yamaha SA2100 f-hole guitar. The original pickups were wired for coil taps with a shielded center tap wire brought out to the cavity switch. Owner didn't care about that, so that wire is coiled up under each pickup. The wire is left long with the ends snipped clean. They are not contacting anything.

Getting this harness in there was a bear, as they always are, but it finally went in (after having to enlarge the metric holes), and everything works.

However, there is a slight hum if either or both volumes are at anything other than full on. It reduces to maybe half if I touch any of the grounds. It does it in either either switch position separately for that pickup, or in both pickups together if either volume is less that full.

All grounds meter out fine to each other from topside, jack nut, all four pot nuts, switch nut, tail stop, and pickups. And again, if I turn a volume up full, it goes quiet.

I sure do not want to have to take this apart yet again. Anyone have any ideas?

https://cdn.shopify.com/s/files/1/06...f?v=1637257474

[The Dude]

The diagram is wrong. The volume pot wipers should go to the switch instead of one end of the pot. The way it's wired, the output isn't grounded with volumes turned down. It's the same scenario as this thread.

https://music-electronics-forum.com/...ange-grounding

Swap pickup and switch connections on the volume pots.

[Randall]

Since you point this out, I think you are right Dude. Makes good sense. I called, and of course this is the first time anyone has raised this issue. Problem for me is, it is installed in an F-hole guitar, so I must take it all out.

Edit: This wiring does in fact work as they have drawn it. I just wired my Les Paul in this way, and it works with no hum, and independent volumes, which is the point in the first place of the 50's wiring. I don't know why it is noisy on the Yamaha SA2100 with humbucker style pickups I am working on. Maybe the lack of any internal shielding? Reversing the lugs makes it quiet, but I lose the independent volume controls, ie. in the middle switch position, turning either volume all the way down kills both pickups. I always thought that was a weird design.

[pdf64]

Ouch!
I suppose the lessons hardest learnt are best remembered

[nosaj]

Since you point this out, I think you are right Dude. Makes good sense. I called, and of course this is the first time anyone has raised this issue. Problem for me is, it is installed in an F-hole guitar, so I must take it all out.

Edit: This wiring does in fact work as they have drawn it. I just wired my Les Paul in this way, and it works with no hum, and independent volumes, which is the point in the first place of the 50's wiring. I don't know why it is noisy on the Yamaha SA2100 with humbucker style pickups I am working on. Maybe the lack of any internal shielding? Reversing the lugs makes it quiet, but I lose the independent volume controls, ie. in the middle switch position, turning either volume all the way down kills both pickups. I always thought that was a weird design.

Maybe CT wound under pickup is picking up noise like an antenna or the fact it is coiled it is an inductor?

Just thinking out loud here. Last f hole I changed the wiring harness on was my last which btw was my first..
last.nosaj

[The Dude]

...... Reversing the lugs makes it quiet, but I lose the independent volume controls, ie. in the middle switch position, turning either volume all the way down kills both pickups. I always thought that was a weird design.

I always liked that design. I will sometimes dial down the neck pickup volume and use it more for a gain reduction. If you want to turn the input gain down, instead of trying to get a volume knob in just the right spot, just flip the pickup switch to the middle position. Each to his own, but I can't see how this configuration is a detriment. Presumably, if you are in the middle switch position, you want a mix of the two pickups, so why would you ever have one of the volumes turned all the way down? Seems like worrying about a scenario that is almost never going to occur.

[Helmholtz]

Another difference:
With the "wrong" wiring inputs and outputs of the vol. pots are reversed.
This means that the pots no longer act as variable voltage dividers. Rather they lower signal by increasingly loading down the PUs.
So with dialing down volume, PU resonance gets killed and the sound gets dull.

[Randall]

I had to put this damn thing together and take it apart three times before I had enough. I don't know why that wiring works on my LP, but not on this Yamaha, but it is what it is. I wired it conventionally, and it works great, Much better than the metric harness that came out of it. I had to enlarge the pot holes, making the owners suggestion to go back to original problematic. I whined about how difficult this was,and how much time it was taking, and he relented to going standard.

Then he told me he was going to sell it. Really? Bill just went up a little.

[J M Fahey]

Wiring pots that way isnīt actually "wrong" (since itīs massively used for the last 60 years or so) but definitely dated.

Way back then nobody cared about dullness (99% of tone controls cut/murdered treble, also in radios, record players and tape recorders) and hum/buzz was a sad but unavoidable fact of life.

Check he famous Jazz Bass wiring .... I donīt hear many complaints about it

[The Dude]

Point taken, Juan. I shouldn't have said "wrong". Maybe "dated", "less right", "more prone to problems", etc. In by brain, that wiring is sort of like asbestos, It was a good idea...... at one time.

[J M Fahey]

Well, it was definitely cheap and simple, plus it saved a pickup selector switch.

And we all know Leo was "cost conscious" .... to say it politely