MV-4F Troubleshooting

Greets!~

I have 3 MV-4F's I'm attempting to troubleshoot in the hopes that I can get at least one working board out of all three of them. Needless to say, I'm just beginning to learn about how everything works..

Anyway, I have boards with the following errors:

• 1st board boots to black screen with white text saying Z80 Error
• 2nd board has cross-hatch only, does not boot any carts
• 3rd board has flipping video with the funky colored test pattern seen during reboot usually.. and funk sound feedback.

I have a 4th that I might be able to use.. it sustained damage during shipping to me, so we'll see how things go there.

Any suggestions on which I should start with? Which board would likely have the least damage based on their output?

Thanks for the help~

THe first mobo (with the z80 error) might not be too difficult to fix. it's probably either a burnt cpu, or a broken trace around the z80 chip. I would suggest busting out a trusty multimeter, and checking the traces from the z80 chip.

Thanks for the help! I will start there and see what I can come up with...

too many probs- not enough time