Strange peaking problem with Carvin MX1644 analog mixer

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Multibomber

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My recently purchased Carvin MX1644 started doing funny things a week ago. Normally, when I turn it on, all the fader peak lights light up very bright as the unit powers on, then the peak lights turn off and everything works in wonderful analog beauty

...but a week ago, the peaking lights started randomly turning while I'm playing... but heres the weird thing: The lights arent lighting up all the way like they do when the unit powers on. The lights just turn on very dimly and stay that way, and you can hear the slight distortion which sounds like peaking. Another weird thing is that I'm only using channels 1-11 right now, but channels 12-16 have their peak lights dimly lit even though there is nothing going in to or through them and the gain and faders are down all the way. ANOTHER weird thing is that channels 4-5 are NOT having the problem. But when I pump up the gain on channel 4-5 and start playing, the peak light doesnt light up all the way like it should, it just barely lights up like other channels, yet it quickly turns off like it should.

Summary of facts:
Carvin MX1644 being used as a mixer for drums
Normally on startup, peak lights shine brightly, then turn off.
During normal operation, if channel peaks, peak light shines bright.
Randomly, peak lights for channels 1-3 & 6-16 will become dimly lit and those channels will slightly distort, even if the gain is turned down all the way and the faders are down all the way, and even in channels 12-16 which have no input.
Channels 4-5 do not have this problem, but if they are made to peak, their peak lights only light up very dimly.
Happens randomly after playing, once it does, I have to turn off the unit for several hours
Fuse holder was broken in transport before I bought it, but I got it to work. It is just floating inside the board but the cap holding the fuse into the black holder is accessable without opening up the board.

Any help would be GREATLY appreciated my friends, Happy Father's Day!
 
Do anyone think I just need a power conditioner? I do have a bunch of stuff running through one outlet... mini refridgerator, stereo, lamp, plus of course my Carvin mx1644 and Roland VS890.
 
Do anyone think I just need a power conditioner? I do have a bunch of stuff running through one outlet... mini refridgerator, stereo, lamp, plus of course my Carvin mx1644 and Roland VS890.
well, that shouldn't be enough to overdraw that circuit. But just to be sure I'd grab a multimeter and check the wall voltage.
The kind of thing you're describing could be from not getting enough juice. But I typically run many times the amount of stuff you're listing fon a single outlet with no problem. But perhaps that fridge draws a lot.
If your outlet shows the proper voltage ..... I have to tell you that the stuff you're describing sounds like a trip to the factory or a tech will be required.
 
LT BOB
Thank you so much for the info! Do you know what the wall voltage should be? Lucky for me, if I do need to take a trip to the factory, Carvin HQ is about 10 minutes away from my nursing school.

Side note about not getting enough juice... If I run two Walmart type space heaters on the same circuit, but not even the same out, the circuit breaker will trip. I just purchased a Furman AC-215 power conditioner on Ebay, I dont know if that will do anything...
 
LT BOB
Thank you so much for the info! Do you know what the wall voltage should be? Lucky for me, if I do need to take a trip to the factory, Carvin HQ is about 10 minutes away from my nursing school.

Side note about not getting enough juice... If I run two Walmart type space heaters on the same circuit, but not even the same out, the circuit breaker will trip. I just purchased a Furman AC-215 power conditioner on Ebay, I dont know if that will do anything...
well, are you in the USA? If so it should be 110-120v .... if you're not in the US then I dunno.
 
I think I would look at the power supply of the mixer first to make sure it's outputting all the correct voltages that its supposed to. There are probably at least 3 separate sections to it such as a bipolar 15 volt section for the signal electronics, a 48 volt supply for the phantom power and then another 6 to 8 volt one for the lamps and LEDs. Having the service manual and a decent meter are essential for checking these things.

Also, if this mixer uses an external power supply unit with a multi pin umbilical cable to connect it to the mixer, you also need to check that cable and all the connection points to ensure proper continuity.

It seems as if there might be some type of internal short that causing this "across the board" issue.

I don't think the 120 volt power in the house could cause the issues described, though a good power conditioner never hurts.

And, if you're not confident in doing these things on your own, definitely let Carvin take a look at it as they've got the experienced technicians to get to the issue quickly.

Cheers! :)
 
The unit uses an internal power supply with the usual detachable power cord. I have a friend who is great with electronics and has some ridiculously expensive multimeter. I dont know if he can read schematics though... Here is the manual for my mixer http://www.carvinservice.com/crg/manuals/mx1644_part_1.pdf

Are there other places on the board that you suspect might cause this shorting issue besides the ones you previously mentioned??
 
The unit uses an internal power supply with the usual detachable power cord. I have a friend who is great with electronics and has some ridiculously expensive multimeter. I dont know if he can read schematics though... Here is the manual for my mixer http://www.carvinservice.com/crg/manuals/mx1644_part_1.pdf

Are there other places on the board that you suspect might cause this shorting issue besides the ones you previously mentioned??

I'm a bit confused on your statement about your friend who you say is great with electronics but you're not sure if he can read a schematic. All I could suggest is to ask him and then you'll know how great or not so great he is. :D

Page 47 of your pdf shows the power supply schematic and the voltages were pretty close to what I thought they'd be. So if your friend can read that diagram, have him check the voltages at the exit points of that circuit to see if they're working correctly.

As for other places to look, I don't honestly know as there's hundreds of places to look for issues.

So, like I mentioned previously, if you or your friend doesn't have the chops to do this, have Carvin give you an estimate.

Cheers! :)
 
Did you buy the mixer during X-Mas time....?

:D ;)

You know what I would do...pick up the phone and call Carvin. Surprised you haven't done that (or at least you have not mentioned it).
They are pretty good on service I think, and a 5-minute discussion with their Tech Dept will probably yield more positive info/solutions than anything else.
Plus...if it is a recent purchase, there must be some warranty. Don't go playing tech on a warranty item unless you really know what you are doing. Let Carvin sort it out...but I can understand, it would be a PITA sending it back to them, though at least you would get it back repaired or replaced if it is under warranty.
 
THE GHOST OF FM
My friend is one of those guys who's busy with a hundred different projects cuz he's pretty good at everything... he brews 4 or 5 styles of his own beer, built his own igloo looking brick pizza oven, made a torch that uses water as its fuel source, and replaced my laptop screen. I just thought if I knew as much as I could when I brought it to him and had a few suggestions, he'd be more likely to section off some time to look at it for me. That's why I appreciate your knowledge so much! I figure smart people enjoy impressing other smart people more than they enjoy impressing idiots :)

MIROSLAV
I did talk to Carvin. Carvin HQ is about 30 minutes away from my house. The board does not have a warranty as it is about 25 years old. WHen I talked to their tech department, they said it could be a million things wrong with the board or nothing wrong with the board and everything wrong with the wiring in my house. Diagnosing the board would cost at least $250 (alas I am a poor nursing student), but actually fixing it would be very easy because the board was made so that everything is replaceable individually. I'd probably end up paying one of the tech dudes to fix it on his own time if it came down to that.
 
THE GHOST OF FM
My friend is one of those guys who's busy with a hundred different projects cuz he's pretty good at everything... he brews 4 or 5 styles of his own beer, built his own igloo looking brick pizza oven, made a torch that uses water as its fuel source, and replaced my laptop screen. I just thought if I knew as much as I could when I brought it to him and had a few suggestions, he'd be more likely to section off some time to look at it for me. That's why I appreciate your knowledge so much! I figure smart people enjoy impressing other smart people more than they enjoy impressing idiots :)
Your friend sounds like a smart guy and I hope you know I wasn't trying to insult him. Many people are very handy and well versed on any number of topics but very few, if any, are experts in all fields and there's no shame in that.

Anyway, my advice is based on what an electronics repair technician should be doing, which is to start with the power supply and then work their way forward down the line. The possible short could come from a defective diode and there are no doubt a great many of them in the mixer. Because the issue is affecting pretty much the entire mixer, it would suggest that the problem is closer to the power supply end of the electric path and is why you look there first. It's a process of elimination, sort of like detective work, starting with the probable, then moving on to the possible and then the least likely.

The other thing electronic technicians use are internal service bulletins for known issues. Some larger companies like Sony, as an example, publish these bulletins on the web. Car companies like GM also do this and that's how car mechanics know how much to charge you for a given repair, because they've worked out the time and parts needed and document that previous work to make other jobs after it a bit easier to do rather then just scratching their heads and guessing. I don't know how detail oriented Carvin is with these types of bulletins. But based on what they told you, they don't seem to keep these types of records...or you just got an inexperienced customer service rep on the phone. It's hard to say.

Finally, I am not an electronics technician by trade. I sold consumer and industrial electronics for 25 years and have known a number of working electronics technicians who have shared a bit of their insight into repairing gear with me. I have done my own simpler repair jobs in the past but have always known when an issue was too complex and handed it over to an expert who eats, sleeps and breathes this stuff.

Cheers! :)
 
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