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Fuse keeps popping on Minimark

Discussion in 'Amps and Cabs [BG]' started by krfoss, May 6, 2017.


  1. krfoss

    krfoss Supporting Member

    Nov 29, 2007
    Orange County, CA
    I just bought a used Minimark 2x6 and unfortunately didnt know it didnt work (I'm pissed, but $50 on craigslist, what should I have expected).

    My question is for the tech savvy out there. What are the most common reasons, and therefore the narrowed down list of things I should check, that the fuse pops immediately once I plug it is. I understand its surging and it could be a busted cap (they all look in tact), could be the transistors on the heatsink (I have no idea how to check those), but could also be almost anything else. I could check everything, but what would you guys/ gals check first?

    Thanks TB!
     
  2. $50? Tech it or wreck it!
    Have a qualified technician look at it or put it out on the curb.

    No user serviceable parts inside.
    If you don't know how to check caps and transistors for shorts, that means you.
    It's not so much about checking for failed parts directly as it is using a methodical process of elimination in the correct order.

    Throwing you a bone. The first thing I'd try is to disconnect the load from the power transformer secondary.
    If it still blows fuses, you need a new transformer.
    If you don't know what that means or how to do it, then tech it or wreck it.

    Either way you go, it's a $50 lesson under the heading of -Try it before you buy it-
    That $50 may save you hundreds the next time.
     
  3. ddnidd1

    ddnidd1 Supporting Member

    Take it to a tech before you damage it further.

    Do not plug it in.
     
  4. krfoss

    krfoss Supporting Member

    Nov 29, 2007
    Orange County, CA
     
  5. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Isn't that an SMPS?

    Troubleshooting is completely different for this type of power supply, especially if there is feedback involved.
     
  6. Jeff Scott

    Jeff Scott Rickenbacker guru..........

    Apr 11, 2006
    IF the speaker drivers are okay, rewire the cab with an input jack directly to the speakers (disconnected from the amplifier) and just use it as a cabinet.

    And then, send the amp chassis to someone who really knows what they are doing to try and repair the amp.
     
  7. Kamatori

    Kamatori

    Jan 20, 2012
    I had a MoMark SD500 that would keep popping fuses as well. It was under warranty so I took it into the shop. About 4 months later I got it back and they told me they needed to replace the entire power supply board.
     
  8. Ooh! Good point. I was thinking linear supply. Bad on me. :rollno:

    I suppose, if it were possible to isolate the PS from the amp that might tell you if one or the other is bad.
    But what is the point if you can't replace boards, or diagnose to component level?

    Is it even possible to run these types of power supplies unloaded?

    This wicket is getting sticky.
     
  9. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Depends on the design of the SMPS, but often the integration is pretty tight and responds to a variety of shutdown/enable signals.

    They can be tough for a pro with the proper test gear to troubleshoot. Almost certainly "impossible" for a DIY'er without understanding how the circuit works, or without the necessary test equipment.
     
  10. PCR

    PCR

    Apr 11, 2008
    I had one of these. There are a couple of ribbon cables inside the amp. The one I bought had come loose during shipping, and didn't power up.

    I would take the amp section out, take the speakers out and check the following:
    - Check the internal speaker wiring for for shorts (including the crossovers)
    - Check all the internal ribbon connections
    - Visually check all the traces and capacitors for leakage

    The one I had worked great, and there wasn't much that could fail on them. I kinda wish I still had it (one of those I regret selling).

    Give that a try first before giving up on it.
     
  11. 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.

     
    Apr 13, 2021

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