I bought a new Tascam Model 12 several months ago from an online retailer and it worked fine for about a month and then channel 1 started muting itself either when the device has been switched on or left for several hours. The only way to “wake” it is if you crank the Gain to the max when there is signal sent to this channel and then it works normally until it goes asleep again.
It looks like a faulty electric component, but I’m no expert. Tascam support didn’t help me much apart from asking me to update the firmware and that didn’t fix it.
I know I can file a claim with the retailer and have it sent for repairs, but I suspect it will take months and I wont be able to use my setup, which is a nightmare. (I am dawless and use the Tascam for multitrack recording of 6-7 synths and samplers).
I don’t have high hopes for an easy fix, but any advices are much appreciated.
If you swap sources (ie plug what’s in 1 to 2 and 2 to 1), does the same behavior happens with channel 2?
I’m asking because maybe it’s something weird with the source, not the console.
Have you tried with only the console and the chan 1 source plugged to the power supply (wall socket), and nothing else?
In case it’s a weird power supply thing.
I don’t own a model 12 but that’s what I would try… but maybe you already thought of that 
Otherwise I guess the ADC or its internal power supply is faulty and there aren’t too many options 
I tried all kinds of sources, but nothing changed. Right now I have the Kick from AR plugged into it, but I’m getting tired of cranking up the gain to max and back again every 20 minutes or so. Definitely something faulty…
Sorry to read that … maybe you can negotiate with the retailer, that they send a new unit right away once they received and checked the defect?
That way you could have a shorter downtime, maybe.