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Mesa amp cut out mid-gig — ideas?

K

kabbz

Jul 3, 2025
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#1
Hi everyone,

I have a Mesa 800+ running into a Mesa 2x10. About 2ish hours into an outdoor gig last weekend, my volume dramatically reduced and shortly after cut out entirely. I was able to get it back momentarily by fiddling with the 'deep' switch, strangely enough. I tried switching to a different speaker output but that didn't do anything. My last pedal in my chain before the amp is a compressor with gain monitoring and the signal looked to be unchanged going into the amp.

I plugged in the next morning at home and let it run for several hours and had no issues. Admittedly I know next to nothing about electronics and am looking for ideas on what could've cause this, how to potentially prevent it in the future and if I'm in danger of my amp cutting out at my gig this holiday weekend.

Thanks!
 
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#3
I have diagnosed a couple of this type of problem recently and in both cases it turned out to be a problem with the pedalboard signal path. Nothing wrong with the amps.

Did you plug directly into the amp and eliminating (not bypassing the pedals) the pedals from the signal path? What were the master LEDs doing when this happened?

I have also seen this where there are severe under-voltage conditions from the power source. There is a low line voltage protect circuit that will disconnect the amp from the power source if it falls too low. There will be no LEDs showing this fault.
 
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#5
Parzival said:
Folks amps are getting overheated. This is like the 3rd post lately with this happening. Had it happen to me and our main soundboard about a month ago. Gotta keep that stuff cool. I bought a mountable umbrella and were running extra fans on stage pointed back at the amps.
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Has nothing to do with cooling, provided the fan isn't damaged, this I'm sure of.
 
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#9
ihixulu said:
I played a 4 hour gig with my 800+ during the recent heatwave in New England. We basically had the Alabama weather @Parzival mentioned. Amp stayed cool the whole gig. I continue to trust the design based on my experiences.

Pedalboards are notoriously common points of signal failure.
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If you keep your amp cool and out of the sun you will be good. I played my Ampeg SVT 7 Pro last Saturday outside for 3 hours and it was good. And we know their history with overheating. (I will say my Ampeg has an upgraded board).
 
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#10
Parzival said:
I'll defer to your wisdom, but you put an amp out in the Alabama sun with over 90 degree temps and 80% humidity, the job of that fan in the amp is a colossal task.
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It's designed around an ambient temperature of ~100 degrees F, into 2 ohms. Humidity doesn't matter to the cooling system. It's very robust.
 
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#12
Parzival said:
That's why I bought a mountable umbrella. In shade you can keep it below 100, but in the sun, it's toast.
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No, it's not toast. The metal surface of the chassis is thermally isolated from the rest of the power amp circuit (for this reason).

I designed the amp, I know what I am talking about here.
 
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#14
Parzival said:
If you keep your amp cool and out of the sun you will be good. I played my Ampeg SVT 7 Pro last Saturday outside for 3 hours and it was good. And we know their history with overheating. (I will say my Ampeg has an upgraded board).
Click to expand...
I don't always have the benefit of shade, and some gigs start or end with my gear in direct sun. I find that I often have a tougher time than the gear when it comes to heat and direct sun. Especially when I mistake beer for hydration lol.

FWIW, my main rig for years was an SWR SM 400, which presented far more challenging heat management issues. The Mesa Subway line is an entirely different animal. At the end of the day, if it can't handle it, it means it ain't the gear for me, but so far Andy's design has lived up to his word.
 
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#15
Been playing in TX ~50 years, if I'm cool enough, amps are cool enough(no direct sun though). Had more trouble with blowing rain and soundguy's spilled sticky drink into the board.
 
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#20
Jason Sypher said:
Hmm. My GK used to cut out AND my SWR used to cut out (in New Orleans) whenever things got really hot…they would suddenly stop and then after a few minutes be fine
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In case you hadn't noticed, his amp isn't a GK or SWR. It's an entirely unrelated design with very different performance and reliability goals.
 
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