Months back I lost the left main on my DL32R... There was very little signal there, while the right was fine.
I called Mackie and for a temp fix, we discussed routing the left main to one of the aux outs in the matrix - which worked great.
Then I performed their suggested fix - unrack that thing, rip it apart and re-seat the ribbon cables. Which fixed that output.
Since then, we picked up noise on one of the drum channels, thought it was a bad cable, so changed that out and still had the noise. Ended up changing to another input on the mixer and all was well. We just had to remember that input 14 was not to be used.... No biggie....
A couple rehearsals ago, a girl that sings with us shows up to sing and that input was now not working. input 5... Changed the cable and moved her to another one and all was well....
Tried it at a show and same thing...
Also, when I had hooked up computer to the system at the previous rehearsal, there was some distortion on input 29... Figured it was a crappy 1/8" to 1/4" cable or splitter.
So today, yanked the DL32R out of the rack and tested the inputs with a signal generator. 5, 14 and 29 all had various issues.
5 was so weird that with a mic cable plugged into it and nothing to the other end, just moving the cable would create noise on that channel.
14 was slightly distorted, a higher level signal would crack, but lower levels were fuzzy.
29 was just the same as its mate, 30, but static.
I unplugged ribbon cables and plugged them back in a couple times.
Now it seems to be working just fine again.
I don't know if it is oxidation that is causing it, but I don't think they are working themselves loose. They are tightly in their sockets.
Now this system does get moved - A LOT... 2 and 3 shows a week and a rehearsal is not unusual, plus it runs sound for some other bands and events at times. We do NOT manhandle it. It's in a rotomolded rack, not shock absorbed, but always carried by me, by hand. It rides in the back of a luxury SUV, not a trailer.
Anyway, if anyone else has low or no input or output, or noise, you might try this. I attached a pic of the insides, nothing to be afraid of here. Just inconvenient.