80's GK 400RB question

TheMinutemen · #1 04-11-2011, 06:42 PM

Strange thing happened today. I have my GK into an Ampeg svt15. When I turned it on today it was distorted, fuzzy and cutting in and out. After a few minutes it cleared up. I could not duplicate what had happened again. I had my buddy stop by with his Carvin 15. Same thing happened, but again, once it cleared up it was gone. I have never had to do anything to this head so I would not be surprised if the time has come. I was thinking it could be the input jack even though movement had zero effect on what happened. Any thoughts? Thanks.

mcm · #2 04-11-2011, 06:47 PM

sounds like the input jack. have the same issue. dang it is annoying

bluesrx · #3 04-11-2011, 06:48 PM

The send/return jacks often get corroded. If you have a spare instrument cable (not a speaker cable) plug one end in the send the other in the return. See what that does.

TheMinutemen · #4 04-11-2011, 07:01 PM

Quote:

Originally Posted by bluesrx

The send/return jacks often get corroded. If you have a spare instrument cable (not a speaker cable) plug one end in the send the other in the return. See what that does.

I will give this a shot. What should I expect doing this exactly? Sorry to sound like a noob, but I never had a problem with it. And for whatever reason, it stopped.

bluesrx · #5 04-11-2011, 07:11 PM

Those send/return jacks are a common problem in the older GK's. They use shorting jacks which when corroded don't short. By testing it with the cable you are just opening the circuit and the cable is just a loop. If your symptoms go away when doing this, you can either leave the cable plugged in or you can spray some deoxit on a 1/4" plug and insert it and pull it out a couple of times. Usually that cleans the jack. If it doesn't, the jacks will need to be replaced.

bluesrx · #6 04-11-2011, 07:17 PM

I had a few early 400RB's and replaced the jacks on all of them.

TheMinutemen · #7 04-11-2011, 07:18 PM

Cool. Thanks alot. I appreciate it. I was using a combo for the last 5 years and this thing sat in my closet and must have gotten corroded. The thing that freaked me out was that it went away, which seemed odd.

bluesrx · #8 04-11-2011, 07:20 PM

Give it a try... you won't hurt anything by doing so...

So the amp hadn't been turned on in 5 years?

TheMinutemen · #9 04-11-2011, 07:24 PM

No. Just playing in the home now so I was primarily using my pre-fender swr workingman. I got sick of looking at the thing just sitting there, it was always a great head, so I picked up the svt15 and sold the combo. Sounds great. Im glad I did it.

TheMinutemen · #10 04-11-2011, 07:25 PM

Time went by quicker than expected...lol. Its been used again for almost a year now.