So, I got a for parts Dreamcast off eBay the other day, and I was told it didn't power on. When I get it, I noticed all the outside screws were missing, so I open it up and the controller port and fan are disconnected, and there is a bag of all the screws I thought were missing and a bag of very used resistors, so clearly someone had been in here before, I plug it all back in, hook it up and turn it on, and I get this video that shakes so fast it's hard to tell it's shaking, but it looks very blurred and you can see it shaking when you look up close. The same set up works perfectly with all my other Dreamcasts. The shell was pretty dirty but the circuit board looks fine and clean enough, so I'm not sure what to look for. I can't seem to find many things through Google on this problem. Also, this is a rev 2 unit.
The four reisistors that were inside for some reason measured at: 11 ohms, 11 ohms (different colors but same size as the first one), and 11 ohms two more times (same colors but smaller than the first one). I think this has something to do with the controller board?
EDIT: I've tried different power supplies and as expected it made no difference. however, I noticed that if I left the system on for maybe a minute, the picture would cut out and I would have to reset the system, sometimes multiple times, to get an image back. I'm thinking this is perhaps something to do with sync? How would I check for that?