So if you have H7 working (aka F800 to FFFF) then theoretically you could get the tester I sent you via message working too. I actually like VOSSI a lot, it's the only tester I had to hand when I started out, PETTESTER is a bit more useful though... e.g. you can test the keyboard VIA as well...
anyway... Either the ROM you are putting in H3 is bad or it is selected at the wrong time... either BA11 is duff or... you have a bad socket or bad trace to H3... a lot of these chip selects are active LOW which is quite unhelpful sometimes as unconnected might result in the wrong device being active.
Send some screenshots as you progress to make the thread more fun!
What a nice thing to find in a skip! Looks like you are making good progress!
Chuck maintains a list of serial numbers; it would be good to add this one into his database.
I have never had to touch my video monitor so other people are better to opine there.
The schematic is at http://www.zimmers.net/anonftp/pub/c...01/video-1.gif
If you have a scope then you can be systematic, or if you want to shot-gun replace then C9 the coupling capacitor is an obvious candidate... and then C12... but it could be anything in that chain.
Divide and conquer should work... base of Q6... base of Q8... base of Q9 and Q10...
Check your V signal has the correct amplitude as well as frequency before going down the video rabbit hole.