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If a mixing board gets too hot ...?


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Will it stop pushing sound through to the power amp/speakers?

 

If not, what else might cause the sound out of all channels to just go silent all at once?

 

It's not either of the speakers. Not any of the cables. The lights flicker to suggest the mixing board is taking the sound in, just nothing's coming out.

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Mixers (not powered mixers) can get pretty hot before there are problems, but it the power supply heatsink is directly attache and part of the top or back plate (like some Mackies), the problems will show up sooner. Generally, one of the supply rails will shut down (regulator thermal protection) and no (or very distorted) sound. Meters may appear to work somewhat if meter supply is different (many mixers use a different rail for LED power to minimize noise.

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Originally posted by happyguitar

DunedinDoug


what's with the relation between TAPE RETURN TO MAIN MIX button on the mackies and heat?

 

 

If you press the Tape Return to Main mix button and nothing is plugged into the tape return you get silence because the only thing going to the main output is the tape return. So if its inadvertently pressed the rest of the channels would disappear.

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Everything's plugged in. No wrong buttons (de)pressed. Faders all good to go.

 

Last band practice we're chugging right along and towards the end of practice, suddenly there's no sound coming out of the PA. No one was standing near it. No one touched it. Just stopped pushing sound to the amp/speakers.

 

Yeah, the board probably gets hot on its own. Probably didn't help that I literally had it sitting directly on top of the power amp (don't rip my head off).

 

You think it's a heat thing, or is there something else I should be looking at?

 

The only thing we did differently last practice than any other practice is we plugged the bass directly into the mixer (channel 6) 'cause the bass player's amp has a loose connection and makes farty noises.

 

FYI - yeah, Mackie 1604 VLZ Pro. Thanks!

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That could definitely have been the case.

 

I just know sound stopped coming out of the speakers. Mixing board still seemed to be receiving the sound 'cause the lights were still flickering. But somewhere between the mixing board and the speakers, the sound got lost.

 

I'm just nervous when I go to the practice space tomorrow and turn everything on the no-sound problem will still be waiting for me. God I hope not.

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Originally posted by kayak

What is the brand and model of the power amp? Also, are there any other devices in the signal chain between the mixer and the speakers, such as an EQ?

 

 

Crest Audio VS900.

 

Currently nothing is between the mixer & speakers other than the amp. I have an EQ & limiter but haven't plugged 'em into the board yet.

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If it happens again, plug some headphones into the program out of the board to see if it is still sending audio. If it is, then you have narrowed it down to the amp. I have a Vs900 and a couple of Vs1100's, and I've never seen them go into shut-down. I would think it would have to be either INCREDIBLY hot, or a speaker wire may have shorted, or there may have been some kind of speaker failure to cause the amp to go into shutdown.

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Okay.

 

So we had band practice last night which gave me an opportunity to check out the PA.

 

You're on target. It had to be a power amp problem. Last night the PA worked just fine. Although I'm not 100% certain the fan in the power amp is running ('cause I couldn't hear it).

 

Anyway, when I had the problem, I believe a red "protect" LED light came on on the front of the amp. It never came on last night (while the PA ran just fine).

 

So what's the protect light mean? What kinda problem am I looking at?

 

Thanks so much for your help!

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Okay, if your only running one speaker per channel, then you aren't putting too heavy load on the amp.

 

Next thing to suspect would be air circulation. The fan on the front needs to be unobstructed, as does the vents on the sides. Did you have anything blocking the front or sides of the amp the night it shut down? Even with the vents unobstructed, I'm still a little suspicious that it may be a heat issue caused by having the mixer sitting directly on top of the amp.

 

Another thing to check would be the connections on your speaker cables; are there any stray strands that might be intermittently shorting out?

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Well basically right now the amp is sitting on top of a shelf, (almost) against the wall with a mixing board on top. Yeah I know, I need to get a good rack for all this stuff.

 

So the face/front is open (i.e., nothing blocking it) ALTHOUGH since the mixing board is longer, it protrudes farther out than the amp. The sides are also out in the open. It's just the top & bottom and back side that are really covered.

 

All that said, I'm really thinking most likely it's a heat/air circulation issue. When I first started this thread I thought maybe the heat from the power amp had done something to the mixing board, so you can imagine how hot the power amp was. Of course in my (LIMITED!) experiences, power amps seem to just get hot.

 

Next time I'm gonna pay more attention to the amp, it's heat and whether I can hear the fan kick in after it's been on for an hour or so. Then I'll report back. I'm pretty sure it's the heat/air and not a speaker connection issue. But I'll triple check connections, plugs, etc.

 

Thanks again for all the advice, words of encouragement, and above all listening to me crying about my PA. You guys are the best resource out there!

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Okay. Latest update.

 

Played with the PA rig a bit more. I'm convinced now more than ever that it's a heating issue. Get this. There's a flip switch on the back of the amp. And when you flip it up, the fan turns on. And when you leave the fan turned on long enough, the protect light turns off.

 

 

 

Anyway, so I think that problem's resolved. Here's my next concern (maybe I should start a new thread?). So now that I think I have the power amp figured out, I'm trying to hook up the EQ. It's a mono EQ. I figured that's what I want 'cause I want to use the EQ for the overall sound, not for individual tracks. I'm not concerned about separating out the drums/percussions on a different EQ. Well not yet, anyway. So yeah, I have a mono EQ.

 

On the board, there's a MAIN INSERT (with 2 inserts). And main outs (for both stereo & mono). On the EQ, there's one input and one output. On the power amp, there are 2 channels (A & B). The way I see it, if I run everything stereo, I'll only get EQ out of one speaker (I'm running 2 speakers). So the way I have it set up currently, I have 1 speaker plugged in & bridged between the 2 channels of the power amp. Then I have the 2nd speaker daisy-chained to it. And I have the power amp plugged into the mono main out of the board. Is this the right way to do it? Or maybe should I get splitter adaptors?

 

(By the way ...) Prior to incorporating the mono EQ, I had both speakers plugged in seperately to the power amp and ran through the stereo main outs of the board.

 

 

ETA:

As always, thanks for all your help!

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And you don't need to bridge the amp if you don't need/want to. You can simply send the same signal to both inputs. If the amp has a switch for parallel inputs, you can use that, or if it has XLR and 1/4" inputs, you can plug the XLR from your mixer into channel 1, and use a 1/4" jumper from channel 1 to channel 2.

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