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Rig shutdown at Gig... any ideas what went wrong?

Discussion in 'Amps and Cabs [BG]' started by ::::BASSIST::::, Oct 15, 2009.


  1. Let It Fall

    Let It Fall Banned

    Oct 15, 2009
    Baton Rouge
    Dude I had the same problem with my lmII it would just cut out sometimes and I could not get it to stay on when I took it to the perfect bass.. I brought it in to a b with a ag500 and my lm2 would work for 15 seconds and then nothing... Other amps worked fine in the same outlet. And this was the only other place I ever brought my amp besides my house..

    So it totally wouldn't work at one place and cut out a couple times at my house, this isn't the first time I have ever heard of this either..
     
  2. mr.hughes

    mr.hughes

    Sep 12, 2005
    Ireland
    Sounds like the amp but I'd keep an eye (ear) on the speakers. I had a UL112 speaker die mid gig for no apparent reason. I had 2 UL112 cabs on the gig, both same age always used together so no obvious reason that one should die and not the other. Took the speaker into Epifani, Nick opened it up. Voice coil was burnt suggesting it had been over-driven, but the cone wasn't distorted/damaged in any way - which he couldn't understand, saying one doesn't usually happen without the other. (So in props to Nick he split the cost on a replacement speaker with me)

    Anyway - good luck, and try using a separate DI so if it happens again you can give the amp a break, see if that's the problem.
     
  3. ::::BASSIST::::

    ::::BASSIST:::: Progress Not Perfection.

    Sep 2, 2004
    Vancouver, BC Canada
    Well, I have a gig tonite and I'll be using the same rig so I'll see how she does. I'm definitely bringing a backup though.
     
  4. svtb15

    svtb15 Banned

    Mar 22, 2004
    Austin,TX - McKinney,TX - NY,NY, - Nashville,TN
    I play it all. Whatever works for the gig. Q+
    Im thinking it may be a switching supply issue with the amp running at a lower impedance @ 4 ohms ..
    even though you are at recommended 4 ohm load on the output, there may not be enough wall current supplying the amp for the peaks.. thus causing the amp to go into protection..

    Im not an EE so i dont really know, its just a theory.

    I dont think it is the fact that you are AB type amp with a switching power supply.. Because my friends LM800 Tube is a Class D and it too did the same thing as i mentioned earlier..

    Maybe it has to do with the Switching Supply??? that is the only common denominator between the two style of amps.

    Perhaps it is the Switching Supply parameters that need to be looked at from a design standpoint of MB when running loud at a 4 ohm load?

    Just a theory. and i dont know for sure.
     
  5. Hey Kirk,

    There are SO many of us running these heads massively hard at 4ohms that it doesn't seem there is an inherent problem. And, he was running at 8ohm when it happened anyway.

    However, any amp will go into thermal shutdown if it gets very hot by being pushed really hard. And this could even happen when really pushing the amp at 8ohms in very rare cases (i.e., showing up at the gig with a much too small rig and turning it way up and really pushing it to compensate).

    My guess is, there was either something funky with the club wiring, or the amp, for some unknown reason, went into thermal shutdown. It's a shame the OP didn't turn it off and then back on. If it immediately would have come back up, then it would most likely be a one time, funky sort of thing.

    The only time I've ever heard of a 'systematic' issue with the MB heads and thermal shutdown is when running two EA NL210's which are known to be significantly below 8ohms, and also a bit power hungry. That results in the poor little LM running at a bit under 4ohms and also being pushed to drive those boxes... a bad combination!

    K
     
  6. ::::BASSIST::::

    ::::BASSIST:::: Progress Not Perfection.

    Sep 2, 2004
    Vancouver, BC Canada
    Yeah it was definitely an 8 ohm load with my single UL112 (again just for monitor purposes).

    Next time I'll shut it off and then turn it on again. The reason I didnt do this is because I did have the FOH sounding good with the LMIIs DI and its better to have no stage volume then no audience volume.
     
  7. Not the way to do it John. Use a vacuum cleaner with a crevice tool. Open the amp and clean out the cooling tunnel with the vacuum and use a clean soft paint brush to dislodge any crud you find on the heat sinks.

    Using the canned air makes all that crud airborne. You never know what has been sucked into the amp could be asbestos and other nasty stuff.

    I'd tend to check the contacts on the jacks in the cabinet. They could need to be re-tensioned or even replaced. Some cabinets have PCB cards doing the interconnections on the jack plate. Often the weight of the plug and cable cause the soldered joints to crack and become intermittent. re-soldering will fix the problem.

    Paul
     
  8. Charles Fields

    Charles Fields

    Mar 30, 2009
    I have not pushed the jack in all the way in the cabinet before that's a possible cause? actually i've done it quite a few time's ,now i stick with the speakons.
     
  9. ::::BASSIST::::

    ::::BASSIST:::: Progress Not Perfection.

    Sep 2, 2004
    Vancouver, BC Canada
    No I checked all connections. That wasnt it.

    Anyway I just finished rehearsing at home at apartment level low volumes with my LMII and the cab in question with no problems.

    I'm beginning to think more and more that it was thermal shutdown.
     
  10. Charles Fields

    Charles Fields

    Mar 30, 2009
    Man i hate when thing's like that happen it's hard to let your guard down for awhile. it's almost better to find somthing wrong so you a least know what the problem was,hopefully it never happen's again,it throw's your game off.good luck.
     
  11. ::::BASSIST::::

    ::::BASSIST:::: Progress Not Perfection.

    Sep 2, 2004
    Vancouver, BC Canada
    Well I just got home from a 4 hour pub gig. The amp and cabs performed flawlessly like they always have. My gain was at 1:00 and my volume at 11:00.

    Something must have happened to cause the thermal to trip at my previous gig. Weird.
    Anyway, I'm leaving a spare amp in my trunk from now on.
     
  12. I had an SWR SM500 that would overheat and shut off. Ended up that the fan was going bad.
     
  13. svtb15

    svtb15 Banned

    Mar 22, 2004
    Austin,TX - McKinney,TX - NY,NY, - Nashville,TN
    I play it all. Whatever works for the gig. Q+
    ooops Im sorry.. I had a brain slippage.. I apologize.. i thought it was a 4 ohm load.. my friends LM800 was running a 4 ohm load when it happens with his..
    I still wonder fi it could be the SMPS?? I dont know.. I only say that since one is a Class D and the other an AB... Just guessing here since no one has anything etched in stone as to what it is. just a bunch of speculation on an intermittent issue so far

     
  14. svtb15

    svtb15 Banned

    Mar 22, 2004
    Austin,TX - McKinney,TX - NY,NY, - Nashville,TN
    I play it all. Whatever works for the gig. Q+
    When it happened Did it just cut out completely? or does it sort of fade out?

     
  15. Nonetheless you should still check the cabinets connectors and ALL your cables. SOMETHING happened and it was a warning. Check everything. Let's face it, you're really going to be needing that amp in the next couple of months.

    Paul
     
  16. ::::BASSIST::::

    ::::BASSIST:::: Progress Not Perfection.

    Sep 2, 2004
    Vancouver, BC Canada
    It cut right out, like the power was switched off.
     
  17. ::::BASSIST::::

    ::::BASSIST:::: Progress Not Perfection.

    Sep 2, 2004
    Vancouver, BC Canada
    I will still look into the one cab, but there is not much I can do as far as the amp goes. I'm certainly not going to drag out the soldering gun. I'd make a mess, plus I dont know what I'm doing anyway.

    I have a GB shuttle MAX 6.0 enroute, so the LMII may very well take backup status.
     
  18. svtb15

    svtb15 Banned

    Mar 22, 2004
    Austin,TX - McKinney,TX - NY,NY, - Nashville,TN
    I play it all. Whatever works for the gig. Q+
    wow thats weird.. running at 8 ohms... and overheating (possibly)??
    unless your fan and heat sinks are clogged with dust, that just seems like a million to one shot..8 ohms Should be a walk in the park even when being pushed.. I have never shut an amp down from temp issues in my life... and i run at outdoor gigs a times in Texas heat with ambient air at 100+ at times.
    but stranger things have happened...

    Im still wondering if it is the SMPS power supply not correcting or able to adjust to a spike or dip..dues to a shift in calibration???? .. possibly triggering because a weird or low current cycle from the wall socket... or it could be the cab.. or if the amp has an effect loop. you may want to clean those contacts .. its nice to do once a year anyway as maintenance



    If it does it when you get your Max6. then you know its something else and not the amp.. my 6.0 and max12 have run at their max in exactly the environment i said above without an issue..
    besides Hasbeen has said in text here on TB that he will eat it if it thermals.. im still waiting to see that day...but my 6.0 and 12.0 run ice cold.. we could sell tickets for charity to watch him do it..:) Just messing ya roger if you read this...

    Keep us posted .. im real curious to what the issue is so i can let my bud know about this... he cant figure his 800 issue out either...
     
  19. Red Planet

    Red Planet Banned SUSPENDED

    May 29, 2005
    Atlanta
    I'm cranky in my old age.
    Sounds like FWER the relay that disengages the output disengaged.

    Could be a heat issue or it could be rthe relay coil going bad. These types of parts go bad quite often, sometimes for no apparent reason. Or it could be something else.

    I have seen a loose wire in a voicecoil cause an intermitent problem. Sometimes it would work and sometimes it wouild not.

    I doubt it was the circuit you were hooked to.

    I would at least pop the top and look for any loose connectios as well as excess dust build up.

    How is your FX loop internal jumper set?

    If it should happen again plug a short cable out and back in the FX loop just to check the jacks.
     
  20. svtb15

    svtb15 Banned

    Mar 22, 2004
    Austin,TX - McKinney,TX - NY,NY, - Nashville,TN
    I play it all. Whatever works for the gig. Q+
    That is a good eval.... you may have nailed it...
     

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