Nice Sony monitor Dex, have one as well.
If the ROMs are dodgy you can try reading them several times to see if you get a different checksum. Hard to know they are complete, and who knows if it ever worked. Didn't know Mame was emulating personal computers now, that is interesting.
Not sure how far you got but if the supplies rails were loaded down open circuit one thing I would have tried is running it up from bench supplies, it could have been part of the problem.
If the Goblin II was a actual product it might be worth repairing, don't think she is a keeper myself unless you are restoring one.
Thanks for posting that, the guys just trolling youtube for vintage computer videos to post here or patting themselves on the back for hoarding junk need to step up.