GK Head Issue

cableguy · #1 06-17-2011, 11:38 AM

I have a GK 400RB-IV. I bought it used. It works fine most of the time but sometimes lately when I turn it on it just sounds weak and fuzzy. Kind of like a blown speaker. I'll actually turn it up and thump the E string a few time hard and it will pop back to normal. It kind of reminds me of an old stereo system that has dirt or something in the volume pot. It will be scratchy until the volume gets turned up, pops and it's fine. I've read about effects loops on these heads getting corroded so I've put a patch cable in the effects send & return during one the times it's done this with no effect on the sound. Has anybody else had an issue like this with a GK RB series head? Any help would be appreciated.

Thanks,

FuzzBoxVoodoo · #2 06-17-2011, 11:42 AM

It wouldn't hurt to clean all of the pots and switches and lube the pots and if it is still there I would pull the cover and tap around inside with it on to see if you can isolate it to maybe a loose connection or a bad solder joint.
Just don't get shocked!

BassmanPaul · #3 06-17-2011, 01:17 PM

Or, you could take it to a tech and have it diagnosed. It could simply be a dirty pot or something else entirely. What FBV suggested is good advice however if the OP has no knowledge of electronics he could end up with a $300 bill instead of a $50 one.

alexofc69 · #4 06-17-2011, 01:24 PM

Ive only ever owned one GK. It was an old 400RB back around 1989-91. I bought used too. It was a great amp and suddenly it did the same as you are describing. I thought it was a fuse, but it was not. So, I called GK and they said to bring it in. They usd to b in Campbell, CA back then and it was just a 10 min drive. I dropped it off and the tech said to give him a few days. A few days later they called me to pick it up. They had cleaned up and boxed like new. They didnt explain what was wrong, just fixed. I didnt care as long as it was working again. It went another year or so and did the same. I ended up giving it away. Give their support a call. They may fix for you. You will just have to pay shipping.

SSCBA · #5 06-17-2011, 01:29 PM

Try cleaning the effects send/return jacks and bypassing them with a cable from fx send to fx return.
That's a very common issue.

cableguy · #6 06-18-2011, 10:32 AM

Thanks for the input guys. I've already had the case apart and didn't see anything that looked off. I may look again a little more closely. I may try cleaning the pots. What type or brand of cleaner has worked best for you? I'm torn about taking it in. Head only cost a few hundred used, it might be cheaper to put the money toward a new head than to spent a hundred or more trying to fix it. The place near me has a minimum $50.00 bench charge. I don't have a problem with the rate, techs have to make a living too. If my amp was a $800.00 amp, no problem. But hard to justify for a $200.00 amp.

craig.p · #7 06-18-2011, 11:09 AM

Cableguy, do what FBV said. Over the decades I've been at this, I've lost count of the DOZENS of amps that behave just like yours and it turned out to be only a solder joint that finally decided to let go. If you can find the exact component that causes the problem to come and go, you can point it out to the tech, he can touch up the solder joint, and you'll be good to go for cheap money.

Also unplug all connectors and plug them all back in -- several times. Things oxidize over the years and doing this will scrape some of it away. Also check ground lugs and ground wires. Even screws that hold circuit boards to standoffs, 'cause sometimes those do double duty as ground points. Unscrew them and snug them up again.