GK 200MB quarantine FB debug session

Discussion in 'The BASS Place' started by Digital Larry, May 23, 2020.

  1. Digital Larry

    Digital Larry Tele-Afflicted Gold Supporter

    May 30, 2017
    Silicon Valley, CA
    30 years ago I worked for awhile at Gallien Krueger. While there I exploited my employee discount to get a 200MB and a 400RB. The 400 RB is on permanent loan to a friend and since I haven't gigged in ages or hardly even jammed with anyone (boo hoo) the 200MB has been parked under the bench for quite some time.

    I did pull it out a year or two ago to hook up to my stereo looper and that was fun. Somewhere along the way I noticed that certain notes would just come booming out and overall it sounded a little distorted, buzzy and slightly rattling regardless of level. I sent an e-mail to GK support and they were nice enough to send me a schematic. I do have a scope and I "could" debug it, but it's not the sort of thing I'd normally choose to do to relax.

    Yesterday I was going back and forth on FB with my former colleague who had done a lot of design and mfg debug work on that and many other amps from that era. After I summarized the symptoms, he said "check the foam surround on the speaker". I got a flashlight, shined it through the perforated metal grille, looked and looked and realized that I could see behind the speaker all the way around. I kinda thought that the foam surround was supposed to be in that space, but it looks like, in fact, it had COMPLETELY disintegrated. Only a very small speck of foam remnants was stuck to one point on the speaker frame.

    Well! At least it's obvious what the problem is. While again I "could" fix it myself, in this day and age I would like to give some work to the local repair shop. Especially after searching over at the TalkBass forum, it seems you can't replace the speaker without completely disassembling the cabinet. Ahhh... not relaxing at all!

    Stay tuned! Get it? Tuned? Cabinet? Bass? (cough)

    Wyzsard and radiocaster like this.
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