So I finally rejoined the ranks of MP-1 owners. While I bought the unit locally, the seller says he bought it off Reverb (original listing here) and I think he may have bought it off an ADA Depot member because there's a website sticker on the top panel. Anyways, The unit is v2.01 and looks to be that way from the factory thanks to the label on the chip. Outside of that, a previous owner had replaced the soldered battery with a newer replaceable battery holder (yay!) and the rear input jack seems to have been replaced since it looks different than the other jacks next to it on the rear panel.
The unit has sound with the S.S. voicing but everytime I switch it to one of the tube voicings, it goes silent (well, there's hiss but no signal otherwise). I wondered if, perhaps, the tubes were blown or bad. I don't have previous experience with tubes but here's what I've done. First, I pulled each tube out and inspected them. They both visually look good with no signs of burning. The front tube is a Mullard 12AX7/ECC83:
The back tube is JJ ECC 83S:
With each tube, I used my multimeter to test continuity from pins 9 to 4/5 and they both were fine & none of the other pins showed continuity. I reinstalled the tubes and then turned the unit on and then took this picture of the tubes after 5 minutes:
I know that it isn't guaranteed that the tubes will glow but neither were in this case. I turned the unit off after this & unplugged it. The tubes themselves were slightly warm to the touch but not hot or scalding. Something was rattling around inside the unit so I took the bottom cover off and found a piece of plastic. It looks like it's part of one of the A/B output jack housings:
I've done pickup & guitar electronic swaps but I'm out of my element with this. Where do I start? Here's a short video where I power up my unit to a patch that uses the S.S voicing. I then edit the patch and try to change it to either of the tube voicings.
Thanks!
Steve