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PA amp problem...or speakers??

Discussion in 'Live Sound [BG]' started by bazza99, Jul 17, 2014.


  1. bazza99

    bazza99

    Aug 19, 2009
    We have a Laney 8300 PA amp that has twice cut out during a gig. This amp is rated for use down to 4 ohms. The first time it cut out we subsequently found one of the speakers was open circuit. We also had the amp looked at, a new thermal fan unit was put in so we thought that would be OK. However, having replaced the dodgy speaker it has tripped out again. Something tells me it's a speaker problem rather than the amp itself. Interestingly, when it cuts out it is the thermal warning light that comes on, not the load protection light!!

    I have now been running it at home using a guitar and a mic with amp connected to a single 8 ohms speaker and it has been 100% fine, no cutting out at all. Questions are:

    1. If the two PA speakers were mismatched, ie one was 8 ohms and one was 5.5 ohms, could that cause it to cut out??

    2. Before buying a new set of speakers, is there any way of testing ie placing a "dummy" load on the amp to see if it cuts out again.

    3. Bearing in mind that we play small places so don't push the amp to excessive volumes, can an amp make speakers go ope or short circuit??

    If anybody can offer any advice I'd really appreciate it. laney 8300.JPG
     
  2. lundborg

    lundborg

    Apr 8, 2008
    1 no
    2 yes
    3 depends on the speaker

    If you experienced problems with a 4 ohm load, testing with an 8 ohm load may not be sufficient. Especially if it's thermal overload.
     
  3. DWBass

    DWBass The Funkfather

    Has this happened at a single venue or different venues? Could be the power at the location. Possibly the outlets are not properly grounded which can cause some amps to act wacky. That used to happen with my Peavey TNT130 bass amp.
     
  4. bazza99

    bazza99

    Aug 19, 2009
    happened at two different venues. I'd really love to know if it's the speakers before I ditch what might be a perfectly good amp!
     
  5. Stereo amp? Are you running both speakers on one channel? It so, you're driving the amp with ~3.25 ohm load, which can cause overheating and cutting out.

    Also, speakers typically go open circuit when broken..
     
  6. bazza99

    bazza99

    Aug 19, 2009
    No, mono amp. Each speaker was plugged into own output. However, we noticed that one speaker seemed to be measuringed at 5.5 ohms.
     
  7. A buddy had one of those which was prone to same cutting out. It seemed to overheat for no good reason, my guess is insufficient cooling system.
     
  8. That's a completely normal DC measurement for a nominal 8ohm cab.
     

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