Blue Startup, Garbled Diagnostic, Passes DeadTest?

[DistantStar001]

So I just got a new c64 board, ASSY NO. 250425, that starts up with a mostly blue screen on startup, with a few garbage characters on the left side of the screen. The Diagnostic cart runs and performs all tests, but I have no idea what the results are since all the characters are garbled. However, it passes the Dead Test with flying colors and clear text?

So far, I have eliminated the RAM, all 3 ROMs, CPU, both CIAs, the PLA, the SID, the VIC II, the clock 8701 as suspects.

 

The board is pictured without ICs, but the ones I installed are good. Any ideas?

[DistantStar001]

Figured it out! Replaced 2 MOS ICs, and discovered that I had a 74LS374 where a 74LS373 should have been.

[DistantStar001]

And then a RAM chip died.

[DistantStar001]

So like I said, replacing U26 made my computer boot normal for about a day, then it went to black. I opened it up, and the transistor at Q3 fell off. I replaced the transistor and ran a Dead Test and all I get is one flash on the screen indicating U12. So I replaced U12 and no change. Reading further in the Dead Test Manuel, I discovered that one flash could also mean either U9 or U21 as they're associated with data bits 1 and 0. I have replaced both chips, and still, all I get is one flash??

 

Any Ideas where this new fault is?