Issue 2: The screen never comes on after I plug in the PFM3. FIXED!!! The issue was that the GND pin of the Boot0 jumper was not making proper contact. I fluxed and reflowed the header pin and now it boots up properly.
I noticed that if I short the Rst and Gnd pins next to the CPU, the screen turns on and I can use the PFM3. All buttons, encoders, menus work and I get sound from all of the outputs. So it seems to be 100% working as far as I can tell, except the screen does not come on until I reset the CPU. Not in regular bootup, not when booting the bootloader via [MENU].
Issue 3: Inserting an SD card causes the screen to go blackFIXED!!! The problem was that I received a TFT screen from AliExpress which had a wrong SD pinout / PCB tracks. It was a "No Touch" version and said v1.0 on the PCB. I ordered a Touch version which says v1.2 on the PCB and it works now.
I reflowed SD slot pins, I did point-to-point tracing, checked for any bridging, it still doesn't work. I tried switching from 5V to 3.3V, no difference.
I tested all of the headers on the board and everything is connecting where it's supposed to go -- LCD headers and SD Card headers, all the way from the TFT board through to the PFM3 mainboard. Nothing is disconnected, nothing is bridged. I have not touched any of the pre-soldered components.
I've built a few dozen DIY synths before, so I'm pretty good at finding bad connections and everything seems fine. Except the screen won't come on at bootup, and putting a card into the SD slot causes it to go black.
TFT module problem? If so, what pins might be the issue? What should I test with my DMM?