Rewiring a Semi-Hollow Guitar

smitty_p

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Some of you ETSG members may remember this thread from there, but I decided to post here as well. This depicts my rewiring of my HB-30 for new pots and caps. Hopefully, it benefits someone here.

I wanted to rewire my Washburn HB-30 for 50's wiring. That, and this guitar originally had 250K pots and .033 uF capacitors. I decided to get 500K, audio taper Bourns pots. I chose Bourns as many comments I've read speak highly of the quality of the construction and the usable taper. Since the F-holes on the HB-30 are somewhat slender and narrower than a Gibson ES-335, I had to get mini-pots, as well.

While I was picking stuff out online, I decided on some .022 mF caps.

Anyway, the pictures below document the process:

First, I made a template of the hole layout. Here's the template with just the pots installed. The abbreviations NV, NT, BV, and BT stand for Neck Volume, Neck Tone, Bridge Volume, and Bridge Tone.

PotTemplateSM.jpg


Here's the template wired up, and ready for connection to the guitar. You can also see the wire enclosed in clear heat shrink that makes a common ground on all the pots.

PotsWiredSM.jpg


The Bourns pots have a larger boss than the other pots I had, so I had to drill the holes slightly larger. This pic shows how I taped the holes prior to drilling to minimize wood flaking. I've removed the tape from one hole after the drilling so you can see how nicely it worked.

The Bourns pots definitely do seem well-built.

I apologize for the messed up color. I was in my garage and the flash didn't go off on my camera.

HolesReamedSm.jpg


Since the HB-30 has it's pickup switch on the upper bout, like a Les Paul, the neck volume and tone are moved quite a bit forward. Because of this, I can get the volume pots in pretty easily. But the tone controls can be tricky. So, I used some aquarium tubing on the tone pot shafts to pull the tone pots into place. Then I worked the volume pots in by hand. This pic shows just before I worked the tubing up through the F-holes and onto the tone pot shafts.

BTW, you can see an "Oops" in this picture. A washer for one of the pots fell through the F-hole. You can see it laying on the bottom of the guitar! Yes, I got it out.

TubingSm.jpg


Here it is all done.

DoneSm.jpg
 
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I'm working on a semi-hollow body rewire job myself. With all the hoopla over shielding the cavity to prevent hum, obviously you can't shield the f holes and in most cases the inside of the body. So my question to you is how is your hum situation?
 
I'm working on a semi-hollow body rewire job myself. With all the hoopla over shielding the cavity to prevent hum, obviously you can't shield the f holes and in most cases the inside of the body. So my question to you is how is your hum situation?

It does hum at high gain, which is to say it obviously hums, but is only noticeable at higher gain, and when I'm not touching metal on the guitar. In practice this never reveals itself because I always use a volume pedal. When not playing, I ramp my volume down.

I've been doing some more researching on '50s and modern wiring. I ran across a thread on The Gear Page where a poster stated his guitar hum is worse with 50's wiring. I don't know how true this is, but it does make me wonder.

I'm tempted to rewire my HB-30 (again!) to use modern wiring and .015 uF caps. Maybe I'll even do a treble bleed.

If I rewire again, I may use full-size pots. I think if I turn them just right, I'll be able to sneak them through the widest part of the F-hole.

I'm never "done" with this guitar!
 
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ur a brave man Smitty for doing such a undertaking. great info thanks

Thanks, Johnny.

But, I gotta say...using the aquarium tubing to pull the pots into place really takes a lot of the headache out of wiring one of these. I can't remember where I found that method; I can't take credit for it.

I played it last night and may just leave well enough alone and not change the wiring again. It sounded really good coming through the house sound and really didn't have any real hum issues.
 
I'm working on a semi-hollow body rewire job myself. With all the hoopla over shielding the cavity to prevent hum, obviously you can't shield the f holes and in most cases the inside of the body. So my question to you is how is your hum situation?

uh... Wave, Humbucking p'ups are designed to prevent this very thing. So in spite of all the hoopla over shielding,
I believe that Humbucker equipped guitars that are properly grounded do not need any.
But I never play a high gain arrangement anyway, so that's where I'm coming from. I don't like the sound of it.
So maybe if I shielded my instruments I'd change my mind about high gain? Probably not. It's just not my thing.

My noisiest guitar is a P-90 equipped Epiphone, but the two p'ups are wired like a big hum bucker, so when I flip
to the middle position, the noise disappears like magic. This Epiphone is a semi hollow body with good quality wiring harness, but zero shielding. I managed to fish the harness back in through the F hole using 10 lb test fishing line.
Caledonia 4x6@100.jpg
 
yes, it is... I bought good parts for the one shown above, because I never want to do that again.
I considered cutting a trap door in the rear, like Les Paul would have done. But I refrained, because
I don't intend to change anything now. I'm hoping that what I bought will outlive me.

Guitarists of the future (if any) can worry about it later.
 
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