Quoted from JBK:MarAlb, tell me more about your test ROM.
Check fuse F6 on the transformer panel down in the cabinet. If it's blown, replace it and turn the power back on. If it blows again immediately, there's a good chance the 20V bridge rectifier is bad. It's the one in the middle. I had a Freddt that wouldn't boot, just GI and random numbers all over the DMD and this turned out to be the problem.