M12 Funky Power Switch

[MartinD]

I just followed Chips video and replaced my power switch (thanks a million Chip).
Unit powers up perfectly now.

However no input signal on connecting microphone to channel 1 (tested that microphone works)
or any other channel. Nothing showing on input meters when I speak into microphone either.
Then I connect output monitor, switch T12 off an on .
Squealing noise that goes from low to high pitched and deafening

So bummed, I thought I'd fixed the only issue, the power switch.
Not sure what to do next! ?

 

[Max Relic]

Next warmly recommended step is contacting Tascam support, your unit must be analyzed by competent technical service.

 

[ScottD_2000]

I had a very similar problem, which is very similar to what everyone is describing here. After about a year of using the Model 12, I would go in a turn it on in the morning, power down each evening. But some mornings I flip the switch and nothing. I was worried obviously. Then I turned it off again and then back on the second time, it almost always went right on, and it was business as usual. (Sometimes it required 2 or 3 times of off and on) So I suspected the building power being dirty, I went and got a surge protector/UPS to prevent spikes and filter the power. Long story short... I did figure out what was happening. I was rearranging a few things on the shelf, which required me to move the wires around. I noticed the AC adapter (the black box part) - that wire was loose! All I had to do was wiggle it and of course press it in harder to make a better connection. I can confirm that's what it was because I have not had one problem since!!