Gallien Krueger Fusion 550 Bad Tube? Help!

Discussion in 'Amps and Cabs [BG]' started by SamuelPaulBass, Jul 11, 2021.


  1. I purchased a 550 Fusion last night off Facebook marketplace and low and behold it sounds like crap when I first plugged it in. I didn’t test it because 1. It was a good deal 2. It looked brand new and powered on and everything seemed to be ok.

    when I tested it late on that night it sounds all distorted and pretty horrible. It’s my fault for not testing it before I bought but I got excited at the low price and well it’s kinda hard to test a head out quick.
    To me it sounds like a preamp tube problem but I’m no technician so it could be something else.
    Any insight would be greatly appreciated.

    https://youtube.com/shorts/_6415b664S8?feature=share
     
  2. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    It’s possible that it’s a tube but there’s a lot going on inside that amp that’s pretty difficult to troubleshoot (even for a qualified tech)

    If you can’t return the amp for a refund, I recommend giving GK a call and see if they have anybody in the factory service department that could work in it, or if they know of any of their service centers that are well equipped to work on this model. This is a clever (IMO) design, but with clever and unique comes significant added complexity.

    This is not a model that an average tech is likely to be successful with, the chances for creating additional damage is very real ime.
     
    TomB, Raw N Low, DJ Bebop and 5 others like this.
  3. Thank you for the input. We have some good techs here in Phoenix so if the tubes aren’t the problem then I will call GK and see what they say. I took a gamble and I hope it’s just a tube.
     
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  4. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    There are enough unusual aspects to that amp that experience with that model will be very helpful.
     
    DJ Bebop and punchdrunk like this.
  5. twinfallsbass

    twinfallsbass Supporting Member

    Jan 24, 2005
    Somewhere in AZ
    Just curious, what amp techs do you know other than Mtronics? Thanks
     
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  6. twinfallsbass

    twinfallsbass Supporting Member

    Jan 24, 2005
    Somewhere in AZ
    And I only assume you already know Mtronics because all local musicians seem to know them LOL
     
    DJ Bebop and SamuelPaulBass like this.
  7. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    I had a couple of friends who worked there over the years but don't know anything about them now. They appear to be connected to Superstition Mountain Music, but that's questionable.

    You really need to give GK a call and ask them who they would recommend for your particular amp and see if perhaps they still repair those at the factory. Of course, these amps are all old enough to be out of warranty and the factory doesn't do much if any out of warranty repairs BUT this is an unusual enough model that there may be an exception.
     
  8. Hunt Amplification is the one I’ve taken my stuff to before and there is another place I was referred to called Field Services.
    Update: wasn’t the tubes :( so now I’m going to take it in to get looked at when I have the time this week. Maybe I’ll learn my lesson from now on.
     
    DJ Bebop likes this.
  9. I’m going to shoot them an email and call tomorrow so see what my options are. Ya can’t with em all
     
    agedhorse likes this.
  10. twinfallsbass

    twinfallsbass Supporting Member

    Jan 24, 2005
    Somewhere in AZ
    I am sorry to hear that it is not the tube.
     
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  11. 1958Bassman

    1958Bassman

    Oct 20, 2007

    Ask if it sat for a long time- tube sockets can oxidize over time and bad sound is a good example of what results. If you look around on forums, you'll see recommendations to 'retension and clean the tube terminals'- I have had to do it and it often works but be aware of what you're dealing with (high voltage, if the caps don't discharge when it turns off) and keep your free hand off of the chassis (put it in your pocket). Caig DeOxit is a good choice for this. You can start by gently wiggling the preamp tubes and doing a visual inspection- if they don't glow, you may have a bad tube, one may have become dislodged or the terminals could be oxidized, as I mentioned. OTOH, it could be a dirty switch that has been unused for years- I have a 400RB and needed to clean my switches because a couple of them hadn't moved in a long time before I adjusted all of them when I checked it out.
     
  12. 1958Bassman

    1958Bassman

    Oct 20, 2007
    GK was very helpful when I called to get info about my 400RB- sent a schematic and she (IIRC, her name is Carol) sounded like a tech. I asked about the 400GT that I had at the time and she knew that one well, too.
     
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  13. RichSnyder

    RichSnyder Columbia, MD Supporting Member

    Jun 19, 2003
    It was hard enough for me to get in-warranty help from GK and then the amp died just after an hour or two of playing after being returned that I’ve written off the brand. Good luck! I hope you can get some assistance.
     
    Last edited: Jul 12, 2021
  14. baxter_x

    baxter_x

    Nov 27, 2013
    EU
    IF it's a tube you can still swap it as it's cheap. But as mentioned earlier, a tube is a very little part of an amp.
     
  15. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    Only the tiniest amount of de-oxit should be used, and caution is absolutely necessary (both for safety reasons as well as not damaging the sockets due to lack of finesse.
     
    Raw N Low likes this.
  16. Raw N Low

    Raw N Low If I can't hear it, hopefully I'll feel it Supporting Member

    Jul 16, 2009
    Denver, Colorado
    These were only discontinued in the last couple of years, so your chances of getting help from GK should be high.
     
    agedhorse likes this.
  17. groovaholic

    groovaholic The louder the better. Supporting Member

    Sep 19, 2004
    Mount Prospect, IL
    Older GK amps, while [email protected]$$, can be prone to oxidation in their effects loop.

    You might want to try plugging/unplugging a guitar cable into the effects send and effects return jacks SEVERAL times each - basically “sexy time at the effects loop”…

    I’ve heard distortion-like problems caused by oxidized connectors.
     
    wave rider likes this.
  18. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    I think he already tried bypassing the loop with a jumper cable.
     
  19. 1958Bassman

    1958Bassman

    Oct 20, 2007
    As always, the instructions should be read. I have seen people flood the insides of equipment with 'tuner cleaner' and washed away any evidence of the component numbers on the board. I have also seen people melt plastic, whether cosmetic or in controls, because they used the wrong type of cleaner.
     
    agedhorse likes this.
  20. TomB

    TomB Supporting Member

    Aug 24, 2007
    Vermont
    Doesn’t GK maintain a “qualified tech” list? I “trained” our local “GK-qualified” tech on this particular amp when I had similar non-tube issues with my MBF500. In my case some connections needed refreshing. It’s been fine since. I’m sure expertise with that amp is out there, and GK does still support it to my knowledge.
     
  21. Primary

    Primary TB Assistant

    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

     
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