The v2 PCBs arrived. This time the order was from pcbs.io as it was cheaper. The trickiest bit would be the FPC connector so I started with that.
At first I tried to tape one side of the connector to the board with kapton while soldering the other side, so it would stay put while I soldered it, but the connector just went up at an angle, so the taped side was touching the board and the untaped pins were touching air. I ruined 2 boards while trying this method by accidentally pulling traces off them.
Then I tried taping the middle of the connector instead (over the middle of both rows of pins) and soldering the corners, then removing the tape and soldering the pins normally. This actually worked! with only minor heat damage to the connector, where I may have accidentally touched the plastic with my soldering iron or with hot solder. Also, I think I missed some of the pins the first time around, but that's no different from the other components.
Anyway, once I got the connector soldered, I went ahead and soldered the rest of the board. A lot more carefully now as if I ruined any more traces, I'd have to do it all over with a dwindling supply of boards.
Powering it up, it all worked, except on VPOS I was getting +13V instead of +15V. It took me a while to realize that I'd gotten the sign wrong and it was actually -13V, and another while to find that the regulator was really outputting +15V, only the output pin wasn't soldered properly. So of course, I fixed that, and now the board works hardware-wise.
Next log will be about software (which I'm still working on anyway).
P.S. If you make this, make sure to set VCOM with the trimpot with the screen disconnected, as the board's max voltage is way higher than the screen's max.
P.P.S. I almost forgot! When the SMPS is on but VPOS and VNEG are off, I'm still getting ~3V for VPOS. Maybe VNEG had some voltage too, I don't remember. Searching about that, I found that that's normal with such SMPS circuits, and if I really want to turn it off I need to add more MOSFETs to switch VPOS and VNEG off. Is there some way to force them to 0V without changing the board?