The 2nd board is still not coming up after moving heatsinks back into position. Looks like an issue with the pic microcontroller on the board not enabling power so I ordered a pic ISD (
pickit 4) to investigate that further. Hoping that Bitmain did not set the read protection on the pic flash so I can read out the firmware to be able to program a replacement chip if necessary, but I'm thinking chances of that are close to 0. If not, it looks like zeusbtc sells a download for pic firmware for all Bitmain's miners.
Well, the problem with this board was not the pic microcontroller. Turns out I was just not looking for its enable signal at the right time. The test jig I have only runs the board for about 1.5 seconds when it doesn't detect any ASICs, and I was measuring the pic outputs after the board had already powered down.
I was able to connect to the pic with the pickit4 and read the pic firmware out of a known good board and use it to verify the firmware in the bad board. So it does not look like there is a need to buy a download... a little sketchy that Zuesbtc is trying to sell it when you can read it yourself with the tools needed to program the chip. I haven't actually programmed a chip with the firmware I read out, so maybe there is some issue with doing that that I'm not seeing. Or maybe some boards do have the read protection bit set and I got lucky.