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help needed for gk 400 rb

Discussion in 'Amps and Cabs [BG]' started by rbass, Jan 14, 2005.

  1. rbass


    Jan 12, 2005
    hey guys, i was wondering if someone here would be able to help me. i am currently using a GK 400 rb bass amp head which looks like it was built in the 80's and am having a problem with it. sometimes it doesnt turn on at all, and it seemed like it was pure luck that it did turn on until i discovered that it will work if i turn the volume knob up to about 2 o'clock. it then bursts on to that volume and doesnt work unless i do that. i was wondering if this would be a fuse problem, or if the amp would need time to warm up , or what? any help would be appreciated thanks.
  2. danomite64


    Nov 16, 2004
    Tampa, Florida
    Well, if the fuse was blown, the amp would not turn on, period. So, it's not a fuse problem. And, because it's a solid state amp, there is no 'warm up' period, so it's not that. It could be something as simple as an extremely dirty volume pot, or an extremely dirty output jack, or something loose inside the amp. I would take it to a tech to have it checked out, but first I might try another instrument and/or speaker cable just in case it's one of those acting up on you.
  3. jgsbass


    May 28, 2003
    Floral Park, NY
    A common problem for early '80's transistor amps is when solder joints gobad and when circuit boards crack. Try turning your amp on at a regular volume. No sound? Tap the head. If you get a signal you have a short due to one of the above reasons. My GK400 had that . I traded it but the head was easily fixed and it is living in its 22nd year
  4. Passinwind

    Passinwind I Know Nothing Supporting Member Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    The effects loop problem refernced in the Walkabout thread below will create that symptom sometimes as well. Try a jumper cable in the EFX loop. There are actually a number of problems that turning up to a certain volume level "corrects". Fractured solder joints or a defective pot are also good possibilities, for sure.
  5. rbass


    Jan 12, 2005
    thanks a lot for that, at least its not anything too bad and ill take it into a tech on monday.
  6. Mickey Shane

    Mickey Shane what goes here?

    Feb 23, 2003
    Denton, Texas
    jgsbass has it right IMO. I bought the same head used a while back. It began to develop the same problems that you are talking about. It WAS old, bad solder connections on the circuit board. The nice thing is that if you remove the top and bottom panels on the head, you can easily get to every solder connection on both sides of the board. I heated up a soldering iron and reheated all of the connections. No need to add solder, and it only took about 15 minutes.

    I put the covers back on, fired it up, and it worked perfectly for many years after the simple repair.