Any equipment gurus here, repair advice

[MetalAges]

I have this bad boy:

Gallien-Krueger 700RB-II Bi-Amp Bass Amplifier

The main volume knob, when turning it up, it just lets out a crazy "static" sound, especially when I am at a low volume level.

I was going to take it to get repaired at the suggested place that's near me listed on the GK web site, but I see a bunch of bad reviews about the place.

Can anyone guide me on how I may fix this issue, or what causes it exactly? I bought the head new a few years ago and really it hasn't been through that much. It sits in one place and usually stays on same volume.

 

[guitarguru777]

Thinking a pre-amp tube but I cant find any specs on the head saying if its tube or not. I see vent slots on the top but those may be just for the power transformer. if it has tubes check them. If not it could be a faulty connection on the input jack to the board.

 

[PhilTheBeard]

You can always try cleaning all of your controls as well with some contact cleaner just in case any dirt or dust has built up in any of your controls.

 

[Lasse Lammert]

might just be a bad pot if you're lucky

 

[sprack]

GALLIEN-KRUEGER700RB.pdf

 

[AHChris]

It´s not tube, our bassist uses this head too. It sounds very nice, but the build quality is really not that good IMHO. Those plastic jacks break easily and I´m not to sure about the potis too. Take it to a tech and hope the best.

 

[Sloan]

Get some DEOXIT, or CONTACT CLEANER (make sure it's non-residue or non-lubricant etc...). spray it in the pot that is scratchy then rotate the pot for a while through it's entire range. this should get it cleaned up again. if not, the actual pot may be loose on the board and will have to be resoldered. not a big deal and shouldn't cost too much at all if you can't do it yourself.

you can even just rotate the knob back and forth really quickly to work out any dirt without contact cleaner, sometimes that works. just make sure you have everything turned down so those loud pops don't slam your speaker.

 

[Omega_Void]

Another thing that can cause pot noise is if a coupling capacitor has failed. These caps are in the signal path to block DC current.

Find the offending pot on the schematic sprack posted, and you can get the cap numbers, which should also be on the PCB. Replacing them will be simple if the solder joints are accessible, but some disassembly may be required to get at them.

Clean the pots first, but if that doesn't help try replacing the caps.