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How to know if a Mackie 408M is even alive

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How to know if a Mackie 408M is even alive

Postby EmperorNorton » Thu Aug 22, 2019 11:14 pm

I hope I'm posting this in the right section (since this looks like something one would use for a live performance rather than post performance studio work) but I assume someone will let me know if I didn't (and maybe an admin can move this to where it needs to be if I did get it wrong). I just bought a large box of studio lighting equipment and buried in the bottom was a Mackie 408M, that at least in the simple physical sense looks OK (no mashed or bent knobs, for example. I have no information on its prior history or what condition it's in (other than I got it from a surplus equipment auction conducted by the University of California at Berkeley), nor any experience with using studio / performance level audio equipment. I just wanted to see if it would even power up before trying to connect anything to it, such as some instruments I have (e.g., electric bass) and other related items (both XLR connector and 1/4" phono plug equipped microphones). So I plugged it in and turned the rocker switch on the back to the "On" position. Saw no signs of life; e.g., a small "Power" LED on the front face stayed dark. Saw no breaker or fuse holder anywhere. The battery backup system I plugged it into did not trip its own breaker, make an overload noise, etc. I found the manual online and took a look at power on procedures and to set it up with gear, it tells you to connect one or more devices to it, then plug it in and turn it on. So did I burn anything out by powering it up without any input or output load attached? And is there anything I missed, assuming I didn't just kill it, about powering it up (such as a secondary front panel "on" switch) just to look for any signs of life? Thanks for any information, or links to such information, anyone can supply here. -- Dan
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Re: How to know if a Mackie 408M is even alive

Postby AlecSp » Thu Aug 22, 2019 11:54 pm

No, you won't have killed the powered mixer by not having anything connected.

About 60 seconds of googling finds that page 27 of the user manual mentions that there's an internal mains fuse, but that it's not user serviceable..

I'd be straight inside to replace that fuse and see if it resolved the problem - of course it may not. Depending on your level of expertise, you might prefer to get a professional to take a look.
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Re: How to know if a Mackie 408M is even alive

Postby EmperorNorton » Fri Aug 23, 2019 1:05 am

Shame on me for not looking for a 'troubleshooting' type section in the manual, which I had already downloaded. My version has the same information you saw as being on the same page where you learned about the fuse: page 27. I got most of the inside works out where I could look around; to get the works far enough out of the case to see everything, I'd have to disconnect control cables going to the front control panel unless there's a way to get that free of the case too. I did find a standard metal-bands-at-each-end-clear-glass-in-the-middle fuse, nothing unusual about its size and shape, which looked intact (unbroken unmelted wire straight down the middle, no burn marks or smoking anywhere). Ohmmeter confirmed continuity in the fuse, so that fuse doesn't seem to be the problem. That fuse is what I'd call the "mains fuse" because it is on the small circuit board where AC power comes into the case before being handed off to the components. All circuit board mounted components I can see look as normal as I could assume they should look, even though some of the ones I can see are hard to get a good look at from a distance; no cracked or smoked transistors, for example. Next step would be to pull out the whole chassis from inside the case to look for other obvious damage that I can't now see well, or at all, or a hidden secondary fuse or two (I've seen that a few times when troubleshooting test equipment). This being an older unit, I'm guessing it would not make economic sense to pay someone to fix whatever's wrong with it unless I get real lucky and find something super simple to repair, so the next step might be a full disclosure 'for parts or not working' listing on eBay so that someone who at least has reason to hope that they can fix this on their own, for their own use, can take a shot at it. So thank you very much, and if I somehow manage to get this working I'll post what I did. -- Dan
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Re: How to know if a Mackie 408M is even alive

Postby EmperorNorton » Fri Aug 23, 2019 1:16 am

Follow up to last post: More out of desperation than anything else I just connected the detachable AC line cord to an extension cord to a power strip, by passing the small battery backup I'd plugged the AC line cord into before. Lo and behold, the green light came on. Maybe there's a problem with that outlet on the UPS I used before. At least I found out before risking damaging the delicate looking many-wires detachable connector that runs from the front controls to a main circuit board inside. Now all I have to do is put it all back together again (about 20 screws) and actually test this for functionality by connecting some audio gear to it. Once again, thanks for your help, and I'll try to remember (it may be a while before I get to the next testing phase) to update this post after the next testing round is done.
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