PA Problems

We set up to play Thursday....oh what a night. I had plenty of time and help to set up the PA, I thought. Got everything put together, 2 mains, 4 monitors, 8 microphones, 3 direct boxes for acoustic guitars.....Mixer is cutting in and out, in and out, almost like it had a noise gate on it. Time to start was closing fast, I had two small mixers with us so I just abandoned the larger mixer and hooked the two smaller mixers together and rewired everything...time is still ticking by, but it is looking workable, then smoke starts rolling out of the back of one of the mains and the input jack is hot enough to melt the plastic jack nut. Pulled that in a hurry. I just abandoned that power amp (had another) and the main speakers and used two of the monitors for mains and the sound turned out great.

What will cause the jack to get so hot as to melt plastic and smoke? Power amp, speaker....I will try it all out again tomorrow, but don't want to cause more damage or risk of life.

My first thought is gremlins. They tried to get you with the mixer and foiled there, they went for the mains.

Just a guess, but a bad speaker cable or bad connector. Are you using speakon or phono plugs?

(With my paranoia I now have to find a back up mixer and back up amp thanks to you.)

Can you be a little more specific? Mixer make/model, amp make/model, etc? How did you have the mixer plugged into the amp, etc. Could make a some difference. Thanks.

I had a mixer that had a bad mic input jack (wire had come off and and was touching ground) but it would blow the fuse when I turned it on.

Sounds to me like your jack on the speaker cab shorted out. I would check that first.

Check your power supply.
Drawing enough energy to create heat, smoke and, not trip a breaker or internal fuse could be a transformer.

Hope you never have to go through that again.

I am going to check it all out this afternoon. Behehringer (yeah I know, I know, there is a big part of the problem there) 24 channel mixer into 2500 watt Behringer Poweramp, speakon at power amp, 1/4 at cabinet. Cabinet is a small, no name, main I have used for years. I will check everything good this afternoon.

You can buy small mixers for almost nothing used. Little 4 channel or 6 non powered Yamahas, peaveys, Behringers for 40-100 dollars all day. With 4 to 6 xlr and often more 1/4" inputs, in a pinch, can power a whole band and take up very little space. We have set up a whole band with good results with just a little mixer, less than a foot square in size and my bass amp with a tweeter in the Cabinet. Everyband should carry one, preferbably with some kind of soft case or safe place (under a car seat?) to keep it. In a pinch amplifiers of any sort with a non powered mixer will make a pa system. Small guitar amps or basses can be used both for powered mains or monitors. I can recall being a little weak with a PA setup at a show and I had brought along a 75 watt peavey ss state amp. Plugged that into the PA system and it really gave us the boost we need on our sound and actually really drives the mids and sounds pretty good. A lot of bands could pick up a couple of cheap ss guitar amps, a cheap mixer as described above and have a pretty decent sounding pa setup.

Just for an update. Removed speaker jack input plate. Both speaker inputs were absolutely fried. They go direct into a circuit board which was also pretty messed up. Removed those and soldered in new switchcraft standard inputs, not into the board, but separate wired to the board rather than directly soldered in. Speaker now works fine. The speakon (at amp) to 1/4 inch (at speaker) cable, the 1/4" end was melted. Replaced it, cord now fine. I think the problem was the 1/4 to 1/4 cord I had to the next daisy chained speaker. It had a dead short across it. Repaired it and all seems to be working well now. I still have a mixer issue that is a separate problem.

I've seen an amp and speaker cab fry from using a guitar cord as a speaker chord.

All the cables I have are the correct ones and very good quality at that. Someone had repaired the end of the 1/4 to 1/4 cable I had and the "tip" side was grounding out against the sleeve that screws over it. It was pretty incredible how hot the one input jack got, it looks like it could have caught on fire for a little bit more.

Are you sure something on the back of your power amp didn't get bumped,like the bridge/dual mono/stereo selector? that wouls cause signal/impedence to be mismatched and burn up the speaker. also are you running all 4 of those monitors on one side of that amp? Causing the load down to 2ohms or lower! Thats gonna be hot enough to burn up a speaker. Unfortunately I myself have seen a speaker actually in flames as I drug it out of a club by the speaker cable. Somebody9a replacement soundguy I hired) took the liberty to rewire my PA.

Are you sure something on the back of your power amp didn't get bumped,like the bridge/dual mono/stereo selector? that wouls cause signal/impedence to be mismatched and burn up the speaker. also are you running all 4 of those monitors on one side of that amp? Causing the load down to 2ohms or lower! Thats gonna be hot enough to burn up a speaker. Unfortunately I myself have seen a speaker actually in flames as I drug it out of a club by the speaker cable. (a replacement soundguy I hired) took the liberty to rewire my PA.

since repairing the cables and replacing the melted input jacks, everything has worked fine. I would not thought the shorted cable would have caused that much problem. There are no switches on the speakers. I had two 8 ohm speakers into one side of a 2500 watt amp so there was a lot of power available there.

Electronic stuff runs on smoke.
Once you let the smoke out, they stop working.
Specialized technicians can put it back in.
It's expensive.