Those boards do indeed look very clean. Let's not make assumptions about what might or might not be good or bad, you'll need to do some actual diagnosis using the schematics.
The only obvious thing I noticed on the second pic, two legs of the 68030 could be touching - check that isn't the case.
View attachment 42989
What happens if you press the reset button with these logic boards? Does it interrupt the sound from the speaker?
Also, what hapens if you plug in headphones, can you hear anything different from that?
Classic II schematics attached. Page 8 has the pinout for the DFAC (Apple sound chip) - things there have to check out because the DFAC is part of the startup circuit.
Check if the RESET line is stuck low, if it is, you won't get any video at all.
The other important part to check is U10 (Egret) - a Motorola microcontroller with Apple code that is responsible for some housekeeping startup/shutdown routines on these machines. It is shown on page 1 of the schematics.
The issue has been covered before, see here:
I just acquired a mint condition Classic II. It was described that it shows only checkerboard pattern. When I got it, it powered on and it showed checkerboard without chime. The HD also starts. Then I recapped it, but now the screen remains blank, also without chime. The logic board was in...
68kmla.org
They had to pull and resolder the Egret before the RESET line would come unstuck. I've had to do this before on Classic II boards as well.
The other thing I'd suggest, using the schematics, is lots and lots of checking of traces and vias - if any are bad, it could lead to the problem.
