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MarkBass LMIII question/problem

Discussion in 'Amps and Cabs [BG]' started by marmadaddy, Apr 26, 2015.


  1. marmadaddy

    marmadaddy

    Oct 17, 2005
    Rochester, NY
    I've had this unit for a few years, love it but last night it started exhibiting an odd issue.

    Ten minutes into a one hour set, output from my cabinets went away. I'm running two MB NYC 604s so it's not an impedance issue. The DI was still working so I had signal to the PA. My first thought was a connection issue so I unplugged the speakon from the back of the head, plugged it back in and had output again.

    This repeated a few times until I just gave up and finished the set.

    My next thought is that I'm possibly overloading the input. But wouldn't that affect the DI also? Any ideas?
     
  2. *Most* amps are designed so that the D.I. is not effected when the amps protection circuits kick in.
     
  3. sloppy_phil

    sloppy_phil

    Aug 21, 2011
    Toronto, ON, Canada
    Not actually named Phil
    Hmmm, the only piece of advice I can comfortably offer is try and plug your bass straight into the 'Return Effect' jack; this should bypass the pre-amp and run you straight into the power section of your amp. If the problem is in the pre-amp, you should still get a pretty loud signal out of your head (which you can probably only control via the master volume), since you're bypassing it. If you still don't get any signal after trying this, chances are there's something bad in your power amp.
     
  4. xk49w

    xk49w

    Apr 13, 2008
    Did the output return immediately when you recycled power (impedance) or did it take some time (thermal)?
     
  5. Does it do the same problem with just one cab plugged in?
     
  6. Silas Stingy

    Silas Stingy

    Feb 19, 2009
    U.K
    I had the same issue running LMII into 4ohm Genz cab, it was mostly solved by running a limiter before the input on the amp, the amp never did this with other cabs.
    Also, there was a known issue with the speakon connector on the LMII, where the connection would work lose during playing, this is solved by using the Jack outputs. Whether this same issue is present on the LMIII I don't know.
     
    rodl2005 likes this.
  7. xk49w

    xk49w

    Apr 13, 2008
    It is possible it is an impedance issue if a crossover broke in one of the cabs. If the LM3 is like the LM2, an over current shut down will latch the amp off until it is turned off which resets it. Reread the OP and that's what it sounds like. It has happened to me.
     
  8. agedhorse

    agedhorse SUSPENDED Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    By any chance have you checked to see that the fan is working?
     
  9. marmadaddy

    marmadaddy

    Oct 17, 2005
    Rochester, NY
    Problem solved. I was running the input gain too hot and the limiter kicked in and did its job .

    I'm too old to be making rookie mistakes like that
     
    rodl2005 likes this.
  10. Some mistakes increase with age :(
     
    Jeff Scott likes this.
  11. As a relatively new Markbass owner (of 2 heads now), this interests me.

    I'm curious how you determined that lowering the input gain was the actual solution and not just happenstance. And when you say it was too hot, how did you determine that? Was the clip light going nuts?

    As someone pointed out above, Markbass lists two types of protection Thermal Protection (too hot/total shutdown) and Current Protection (likely too low impedance or bad cable/signal to speakers stops - Pre & DI keep working).

    Clearly, what you experienced was Current Protection. It seems that if one of the solutions to this issue was to simply lower the input gain, Markbass would include that in their troubleshooting tips.
     
    agedhorse likes this.
  12. marmadaddy

    marmadaddy

    Oct 17, 2005
    Rochester, NY
    The clip light was bright blue.
    I tested by significantly lowering the output level of my VT Deluxe, which is the last thing in the chain prior to the amp. I played for over an hour at this level with my highest output instrument with zero problems. I am going to be switching out the speaker cables at my next gig to avoid taking any chances.
     
  13. Well, that does seem to point at potential cause and effect.

    Interesting.
     
  14. sloppy_phil

    sloppy_phil

    Aug 21, 2011
    Toronto, ON, Canada
    Not actually named Phil
    Yeah, sometimes MB amps don't like being totally slammed in the front end; probably the reason they include the clipping light. Maybe this isn't what I would have assumed the problem would be, but cool that you figured it out all the same.
     

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