And you may ask yourself, do I REALLY want to do this?

[ReginaldBisquet]

The patient:


2009 Gibson SG Classic.

The issue:
Latent desire to switch out volume controls for 500k audio pots. However, this is one of the new circuit board control panel guitars from Gibson. Let's take a look:



The inside looks nice and neat. When the board is removed, the cavity is clean and plenty big for installing traditional pots and wires:



And now a view (or two) of the circuit board:





Out of curiosity, I measured the readings of the potentiometers in this guitar:

Bridge Volume: 305k
Bridge Tone: 458k

Neck Volume: 296k
Neck Tone: 412k

And yeah, the volume doesn't quite let the pickups bite as hard as my other P90 guitar. I especially noticed this the other night at a gig when I had to switch guitars due to a broken string... and noticed right away how the Gibson had a softer attack.

The guitar still sounds great, but I like that bark from the P90s and want to see if the change in pots will help bring that characteristic to the front.

So... do I really want to mess with this thing? There are five solder points on the circuit board for each pot. The ceramic capacitors (0.022) have two solder points and are quite easy to remove - much like working on a pedal.

I'm guessing (at this point) what I'll have to do is trim the round ends of the lugs on the pots so they are straight and then find out if Gibson simply uses a large goop of solder on the sides of the pots... or if there's something else making the connection between the pot and the board.

Has anyone worked on one of these recently?

[Kazooman]

Nope, never touched one of these, but it doesn't look like it would be too difficult. However, it would be nice if you could try the substitute pots without first messing with the board to see if you can get the sound you want. Are the connectors from the switch and pups generic so you could get the pieces to make your own test circuit? Actually, if you have another switch you could just solder that one in place. I would hate to mess with the board only to find that the secret to the magic sound lies elsewhere.

[Mark Hammer]

If it was me, I wouldn't touch it. That preassembled board is probably one of the only smart things Gibson has done since 2000. Lovely piece of work.

Here's what I would do instead, though.

Get yourself a piece of copper board from an electronics outlet that is big enough to replicate the existing assembly. Trace the existing board and cut the double-sided board to shape/size. Drill holes in the appropriate places (once it is the right shape to fit in the cavity, you can slide it in and trace where the holes go from/through the top of the guitar). Smooth the edges.

Now you can install whatever pots you want as a secondary assembly, and if you should ever wish to sell the guitar, you can just pop the original assembly in there, go snap snap snap, and its stock again. The big challenge is to have your retrofit board be compatible with the snap-in connectors, but we can figure that out as we go along.

Finally, as I am fond of telling people, the relative advantage of different value pots will ultimately depend on how you use your volume pot. If you're the kind of player who leaves it on full 90% of the time, then yes you will find 500k preserves a little more bite. If you're the sort who is always frittering around with the volume setting, then swapping 300k for 500k won't provide any real advantage.

[Mandopicker]

Would it be possible to change the value of the pot by just soldering the appropriate value resistor to the outer legs of the specific pots to increase the value closer to 500K?

For example, I know that if you have A 500k and want to change its value to a 250K, you would just solder a 2 x1 meg resistors (or a single 500k resistor) in parallel to the outer legs. (I read about this mod on the net and have successfully tried it.)

The taper will probably change, but at least you'll be able to play those P-90's wide open.

Never tried to make a pot bigger, but heck I could be wrong. The experiment would be fun if you have a bunch of resistors to play with. Perhaps with some simple calculations and the right resistor, you could make the current pots closer to 500K. Just solder it to the area you can easily reach of the current setup. The resistor can easily be removed later.

Anyone else out there...please do correct my logic if wrong...I'd like to know for sure.

[Robert M. Martinelli]

Nope, that works only if you want to make the pot's value smaller, say from 500K to 250K or so (and yes, it does alter the taper).

By soldering a resistor on the outer legs of a pot you have to think that you're actually putting the additional resistor in parallel with the pot itself, so the resulting total value can only be smaller.

Hope this helps

Best regards

Bob

[David Schwab]

That board probably has plated through holes. It's very difficult to unsolder parts from those without damaging the board.

[pdf64]

Bear in mind that the load on the pick up, with regard to the controls, is the vol pot IN PARALLEL with the tone pot resistance (at audio frequencies, with the tone set high, the cap is effectively a short). So for a 300k vol // 500k tone total is 188k, whereas for 500k vol and 500k tone, total is 250k. Not a big difference, more likely to be other reasons for the tone discrepancy.
And a 300k vol pot (compared to a 500k) will reduce treble loss as it's turned down.
However, if you're determined to get an effective 250k total loading, you could modify the track of the tone control by removing a little of the carbon track at the '10' end, until the total resistance is around 1M5. Use a scalpel blade to scrape, or abrasive paper to rub away, the track material.
300k // 1M5 is 250k.
Practice on an old pot first.
Same idea as Fenders 'no load' tone pot.

[Steve Conner]

One downside I can see is that the control cavity isn't shielded. It's probably a double-sided PCB they used, with shielding built in. But if you rewire with new parts and no PCB, you'll need to add some copper tape or whatever.

The PCB setup is so neat, it would be a shame to spoil it, hack the connectors off the pickups, and so on. But deep down you know you want to

[ReginaldBisquet]

Other notes:

The input jack is a Switchcraft brand jack. According to the serial numbers stamped on the side of the pots, they are made by CTS with brass shafts. The connectors are made by Molex (part # 43645). Cost about $0.50 each from Mouser:
43645-0200 Molex Headers & Wire Housings

The P90s in this guitar are held by a brace under the pickup that attaches to the pickguard:


And interestingly enough, the route in the pickup cavity is just large enough to accommodate a humbucker if you wanted to switch. You'd need a new pickguard of course.



Note that the wood screws on the top of the P90s don't go all the way though the pickup!

[David Schwab]

Is that an upside-down brass humbucker baseplate under the P-90?

[ReginaldBisquet]

Two more photos: