Help with Mixer Intermittant Audio Drop Out

Hi there,

I don't have enuff hair to start pulling it out!

I have a B-word MX2642A mixer that has recently decided not to output signal on the left channel but only now and then. Sometimes goes for hours without a problem and sometimes goes out for hours........ Sometimes goes in and out every few minutes...... It's an adventure!!

The weirdest thing is it happens on the main outs, the sub outs, the aux sends, the control room outs, the headphone outs.

Did I miss anyone?

I've checked cables and everything else I could think of. Changed cables, inputs, speakers, amps, all quite a few times..... I am stymied.

Anyone got any ideas as to what this would be??

Thanks!!

The simple answer is that it's broken. It might be a bad solder joint, a bad component, or a poor connector.

Generally when you lose all the outputs, it's because you've lost the input channel since the all of the output buses come from different points in the input channel. When it's doing its dead thing, do ALL input channels lose the singal on the left output? That would be bad. But if only one channel behaves that way, just move your source to another channel until you have a chance to get it opened up and repaired.

Hi Mike,

Yeah, any input to any output group. Is there anything I can do by opening her up and looking around to try and find the problem? All I have is a nice test meter.

I've been told it might be a ribbon cable or it's conectors OR the main insert point may have been rendered un-normalled by crud. I'll check those out.

Do you think a bad power supply could be the culprit?

Thanks for the response,

Rob Cathcart

I knew I replied to this message somewhere. I just saw a follow-up to it in rec.audio.pro

That's pretty odd, but I don't know how that mixer is constructed internally. If it was one channel or one bus, I'd suspect that a ribbon cable connector had come loose, but half the outputs from all the inputs is a bit puzzling. If you lost the left main output or the one of the group outputs, or an auxilary send from any input, that would be easier to explain. But if you're sure that you're losing the left of whatever output a channel is assigned to plus the pre and post fader auxiliary sends, that's pretty strange.

Start from scratch, and check out output at a time when it's in its "failed" mode and see if you can narrow it down. It's easy to compound your symptoms if, for instance, if you're assigning an input to Group 1-2 and then assigning Group 1-2 to the main mix, I can see how you could lose the Group 1 output and the Left Main output, but the aux sends should be indepependent (and they're not right or left anyway).

It's not likely that you'd find the problem with a meter. A set of headphones with clip leads and test probes so you could trace the signal through the path from input to output would be more useful, but you'd need a schematic or preferably a service manual for the mixer. That may be getting too advanced for you.

It could very well be a ribbon cable if the symptoms were right. If the insert jack was cruddy, that could cause the problem as well, but only with the signal that the insert is in the path of, and there aren't any inserts on the groups.

The power supply would be about the last thing I'd suspect, unless it was a connector from the power supply to the board that carries the outputs.

I had a similar problem with my "B word" UB2442 and found the solution on the Mackie forums quite some time ago.

These style of mixers use cheap computer style pressure fit ribbon cable connectors that need to be pressed down occasionally.