DIY repair, a power surge, a mixing console, and me.

mockd · 26th March 2010, 10:03 PM

Hi everybody.
I'm posting to get some advice, or perhaps to be pointed in the right direction. The backstory: some friends of mine had their Mackie 408M mixing console blown by a surge when the venue's sound man hooked it up to a generator which was malfunctioning. They didn't have time to mess around with repairing a twelve-or-so year old mixer, so they bought a new one. They were going to throw the broken one out, but I told them I'd like to take it and try to fix it, and they then said I could have it.

They're on the road right now, so I haven't had a chance to open up and look at the unit. My question is this: before I ask them to drag it all the way back here, is there a chance that it is fixable? I realize that this could depend on a whole lot of variables. I'm just wondering if it's possible that the unit is salvageable, and if so, if I would have to invest very much into fixing it?

If it is salvageable, any tutorial suggestions or hints as to what I'd have to read up on would be greatly appreciated too. Thanks

bob91343 · 26th March 2010, 10:16 PM

Sure it's repairable! First, pop the cover and look for burned parts. Power supply is the first place to look. Get a diagram so you aren't working blind. These are not complex devices, at least considering what the problem here is.

Xoc1 · 26th March 2010, 11:11 PM

I see that a 408m is a powered mixer.
The mixer section is likely to survive as it would be regulated. The power amplifier could be another story altogether

prairiemystic · 26th March 2010, 11:34 PM

It's surely worth a look to fix it. Generators can overvoltage to the point where IC's short, filter capacitors fail and leak etc. hopefully just the fuse went. If it's 12 years old it will be pretty durable.

Enzo · 26th March 2010, 11:45 PM

All we really know is that it was on generator power, and it no longer works. Did it receive 150v? 800v? Reversed neutral and ground or something? We have no idea, consequently we have no idea what is wrong with it. We have to find out.

Isolate the problem. If it is "dead" as in no signs of life, then start with power supply. Is the main power supply even getting mains voltage? You could have a burnt out inrush limiting thermistor or something or a dead varistor somewhere. Oops, no inrush part on the 408.

I agree the power amps are the most suspect. Try disconnecting them.

And contact Mackie at Loud Technologies and request the schematic set for your mixer.

mockd · 27th March 2010, 06:56 PM

Thanks a lot for the replies!

When I get my hands on it, I'll open it up and see what story the power supply tells and move on from there. And get in touch with Mackie, too. Thanks again for the advice

26th March 2010, 10:03 PM	#1
mockd diyAudio Member Join Date: Mar 2010	DIY repair, a power surge, a mixing console, and me. Hi everybody. I'm posting to get some advice, or perhaps to be pointed in the right direction. The backstory: some friends of mine had their Mackie 408M mixing console blown by a surge when the venue's sound man hooked it up to a generator which was malfunctioning. They didn't have time to mess around with repairing a twelve-or-so year old mixer, so they bought a new one. They were going to throw the broken one out, but I told them I'd like to take it and try to fix it, and they then said I could have it. They're on the road right now, so I haven't had a chance to open up and look at the unit. My question is this: before I ask them to drag it all the way back here, is there a chance that it is fixable? I realize that this could depend on a whole lot of variables. I'm just wondering if it's possible that the unit is salvageable, and if so, if I would have to invest very much into fixing it? If it is salvageable, any tutorial suggestions or hints as to what I'd have to read up on would be greatly appreciated too. Thanks

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26th March 2010, 10:16 PM	#2
bob91343 diyAudio Member Join Date: Mar 2010	Sure it's repairable! First, pop the cover and look for burned parts. Power supply is the first place to look. Get a diagram so you aren't working blind. These are not complex devices, at least considering what the problem here is.

26th March 2010, 11:11 PM	#3
Xoc1 diyAudio Member Join Date: Nov 2008 Location: Devon UK	I see that a 408m is a powered mixer. The mixer section is likely to survive as it would be regulated. The power amplifier could be another story altogether

26th March 2010, 11:34 PM	#4
prairiemystic diyAudio Member Join Date: Jul 2004 Location: Edmonton, AB Canada	It's surely worth a look to fix it. Generators can overvoltage to the point where IC's short, filter capacitors fail and leak etc. hopefully just the fuse went. If it's 12 years old it will be pretty durable.

26th March 2010, 11:45 PM	#5
Enzo diyAudio Member Join Date: Sep 2004 Location: Lansing, Michigan	All we really know is that it was on generator power, and it no longer works. Did it receive 150v? 800v? Reversed neutral and ground or something? We have no idea, consequently we have no idea what is wrong with it. We have to find out. Isolate the problem. If it is "dead" as in no signs of life, then start with power supply. Is the main power supply even getting mains voltage? You could have a burnt out inrush limiting thermistor or something or a dead varistor somewhere. Oops, no inrush part on the 408. I agree the power amps are the most suspect. Try disconnecting them. And contact Mackie at Loud Technologies and request the schematic set for your mixer.

27th March 2010, 06:56 PM	#6
mockd diyAudio Member Join Date: Mar 2010	Thanks a lot for the replies! When I get my hands on it, I'll open it up and see what story the power supply tells and move on from there. And get in touch with Mackie, too. Thanks again for the advice

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