Ibanez Gio bass wiring is strange!

[Guitarsrmine]

Hi everyone e. I recently purchased a used Ibanez Gio 4 string bass with the PHAT EQ. But in the place of the tone potentiometer I believe someone put a half-baked volume control in! The pot works, for sure. But it’s definitely not a tone pot. If you have both pickups on full, this “ mystery pot” will turn them down!! I’m not an electronics whiz. Anyone have any input?

 

[Snert]

Isn't it a balance, not a tone? Check the Ibanez website as it will detail the working of all the controls.

 

[Guitarsrmine]

Isn't it a balance, not a tone? Check the Ibanez website as it will detail the working of all the controls.

It’s not a balance pot. Each pickup has its own independent volume pot. The pot in question does change the tone, but when you’re at the no-treble side of the pot,(entire way counter-clockwise) the volume goes away, about 99% of the volume anyways.

 

[thisSNsucks]

That’s not a feature on the bass, if the volume cuts out when tone is rolled off it could be that the leg of the cap is hitting the pot casing on the side it’s connected to the pot lug. Or sometimes an internal issue with the pot wiper. Sometimes even dirt can cause it.

 

[Crater]

Tone pot appears to be wired incorrectly...none of the terminals on the tone pot should be connected directly to ground, but it appears the center terminal is connected by the bare wire to the ground on the back of the pot case. Only one leg of the tone cap should be connected to ground, other terminal on the cap is connected to the outer lug of the tone pot.

 

[dwizum]

I zoomed in and highlighted the likely problem spot.

The tone cap is the big orange square thing. It's left leg (red line I drew in) goes to ground. It's right leg (not highlighted, but visible) goes to the right most terminal on the pot.

The hot signal wire from the jack is soldered to the center terminal on the pot. I highlighted the center terminal in green, it's below that white wire.

The likely cause of your problem is that the pot leg (red line) is unintentionally touching the center terminal (green circle).

If you move the white wire to the side, you may be able to confirm this. Or take another photo and show us if you're not sure. Sometimes, the solution is as easy as gently bending the terminal on the pot or the leg of the cap so they stop touching.

The way that tone cap was positioned when it was soldered is pretty poor. If it were rotated such that it formed a straight line from the right terminal to the solder point on the back of the pot, this wouldn't have happened.

 

[fig]

Hey, @dwizum, does that outer lug of the pot where the cap's connected (lug 1 in your enlarged pic) look like it's barely touching the wall of the control cavity? If that's a conductive coating in the cavity, that might be a problem, too. For my own sanity, I'd rotate that tone control back a little LOL

 

[dwizum]

Yeah that does look likely! And actually that would match the symptoms the OP reported a little better I think...

Rotate the pot and/or put some insulating tape there.

 

[iiipopes]

Folks, I have the predecessor of this bass. The basic wiring is V-V-T like a J-bass, then Ibanez added the "Phat" control. The "Phat" control is Ibanez' version of the EMG EXB. It simultaneously and progressively adds bass and treble, hence the battery to operate it. Here is a line drawing to help figure out if anything is amiss.

 

[MidlifeBeginner]

Yes, sounds like a short either in the pot or against the terminal as described.
Other possibility is the pot rotating and a terminal making contact with shielding paint on the side.

Easy fix, a bit of electrical tape over the terminals of that pot.

 

[Guitarsrmine]

The PHAT control works as intended . It’s the tone knob that’s the only issue-and thank you ALL for your input!!