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LMII Cutting Out

Discussion in 'Amps and Cabs [BG]' started by RBasss, Oct 1, 2008.


  1. RBasss

    RBasss

    Dec 13, 2006
    Richmond, VA
    East Coast Sales Coordinator - Crafter Guitars
    I've got a LMII that I've had for a few months now (bought new at GC). The amp cut out a few times when I was rehearsing with my band the last night. It did it when I played on the high D or G strings a little harder than usual. This was with a stock Epiphone Goth Thunderbird. I am very concious of where my input gain is set and always make sure that I do not activate the clip light when playing. I never saw the clip light even come on before the amp would cut out. The amp would just stop putting out sound. I would turn it off for a few seconds and turn it back on and it acted as if nothing ever happened. It did this 3 times last night at different times. Is this a protection issue with the onboard limiter? Should I use a compressor in front of the amp to keep peaks down? I have my EQ on the amp set fairly flat with just a slight boast in the low and high mids at around 1 o'clock. I don't have the VPF or VLE knobs on at all. Gain is set at about 10 o'clock and my master volume is around 11 o'clock. I do have an MXR M80 DI in the effects loop that I use for coloring and overdrive but I had it set to work with the input gain of the amp to not produce clipping. Is there a fault with my amp? Should I take it back to GC for replacement? Anyone other LMII owners have this happen? I have a big headlining gig this weekend and I do not want to have any issues during my set. Any suggestions are appreciated.
     
  2. I had this exact thing happen - it was a faulty speaker that when overdriven would seem to short and engage the LMII output protection circuit. See if it happens with other speakers.
     
  3. I had this happen live when playing it through a single 8ohm cab. I thought it was broken, but found out later it needs 4ohm. I don't know if this would fix your issue, but once I found a nice matching cab I never had any further problems with the amp cutting out.
     
  4. mynan

    mynan

    Nov 7, 2007
    Grand Haven, MI
    That's not true.
     
  5. Shouldn't matter what ohm speaker you run as long as you don't go below the LMII's 4ohm limit.

    I would take it back to GC. There's Markbass rep that's a member here. Can't remember his username.
     
  6. mynan

    mynan

    Nov 7, 2007
    Grand Haven, MI
    The amp has a protection circuit that...protects the amp. It can be set off by any of a number of factors...overheating, overloading caused by a bad cab, fluctuations in the power going into the amp, etc.

    It may be a problem with the amp, but probably not...and if it's not the amp, be glad that the protection circuit is working instead of your amp blowing up.
     
  7. RBasss

    RBasss

    Dec 13, 2006
    Richmond, VA
    East Coast Sales Coordinator - Crafter Guitars
    I'm running it into a 4 ohm 810E. Do you think that's the problem? How do I check that a speaker is faulty or not?
     
  8. Guest043

    Guest043 Guest

    Apr 8, 2008
    i think its likely to be speaker trouble..not markbass trouble..

    maybe i just dont want to believe a LMII could ever fail.
     
  9. This is incorrect.
     
  10. Peter Murray
     
  11. craig.p

    craig.p

    Sep 28, 2008
    New Hampshire
    1) Is there a fan in this unit, and if so, is it working?

    2) Was there any audible distortion before the amp went down? Any signs of clipping?

    3) Suggest you go back to the effects and settings you used last time the amp was working properly, start playing like you did at the time, and see if the amp falls down again. In other words, establish a trustworthy baseline from which you can do your diagnosis.

    4) Line up a spare for your job this weekend, even if you have to rent one.
     
  12. I got it. It doesn't need a 4ohm.

    Sorry for the misinformation. I need more coffee.
     
  13. RBasss

    RBasss

    Dec 13, 2006
    Richmond, VA
    East Coast Sales Coordinator - Crafter Guitars

    1 - There is a fan and it is working.
    2 - There was no audible distortion before the amp went down. As I said in the original post I saw no clip light come on before it shut off.
    3 - I've got rehearsal again tonight so I'll see what happens.
    4 - Good idea, I'm friends with both bass players in the other 2 bands that are opening for us so I'll probably see about borrowing one of their setups.

    Is there a way to go through and check the speakers in my 810E to see if they are faulty or not? I can run it as 2 separate 8 ohm 4x10s. Should I try this and see if I can get one to go out or not. Thanks so much for the quick replies by the way.
     
  14. Rugaar

    Rugaar

    Apr 11, 2007
    wisconsin
    A guy over at the FDP forum had a problem with his LMII. Check out the thread for his info. Might be a similar situation.
     
  15. Jefenator

    Jefenator Supporting Member

    Aug 22, 2008
    Oregon
    Very handy to be able to split the 8x10!

    With a digital Volt/Ohm meter you can measure the resistance over the speaker connections for each half of the cab. Each one should read somewhat less than 8, somewhere in the ballpark of 5-6 ohms. If one reads much lower... bingo! You know which half is bad. If you're feeling technically empowered, you can get in to the guts and find out which specific driver is bad.

    The amp test might be more practical, especially if the flaw is undetectable except during operation. You might find however that neither side by itself will make the amp go into protect mode. (Aren't intermittent electrical faults fun???)

    Hopefully you can get through some gigs with the "good" half of your cab till you get it all fixed. Good luck!
     
  16. If that doesn't work, guessing it's a faulty power amp. (Which was the issue on the FDP forum noted below). Take it back & exchange for another one. Could be loose or faulty compent on the PCB.
     
  17. RBasss

    RBasss

    Dec 13, 2006
    Richmond, VA
    East Coast Sales Coordinator - Crafter Guitars
    I'm going to try to pick up an volt/ohm meter before I practice tonight from Radio Shack. What do I touch the leads of the meter too on the 810?
     
  18. Mine cut out on me for a few seconds at an outdoor gig. And the guitar player's amp blew a fuse on that gig. Couldn't a power surge cause it? If so, maybe a power conditioner will cure it.
     
  19. RBasss

    RBasss

    Dec 13, 2006
    Richmond, VA
    East Coast Sales Coordinator - Crafter Guitars
    I've got a Furman PL-8 in my rack. I'm going to see if I can get a volt/ohm meter right now...
     
  20. Are you sure it's not the jack on your bass, or bad wiring of your pickups?
     

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