Hi Ian,
I would try the board with just U6, U9, U11 installed and all other socketed chips removed first. The board can start the first test with just these 3 chips + the other soldered in chips working. The other socketed chips are faulty they can stop the test from running.
It depends if the Dolly Parton has the same type/number of Roms installed as the Xenon, but if they do you could also try U6 in the Xenon to verfiy this is working.
If the U6,U9,U11 check out (and you have already tested U9, U11) you are looking at one the soldered chips which has failed or possibly a damaged track in the corrosion area. Sometimes the tracks look fine but actually don't connect when measured with a meter.
I have replaced a few U16 chips on these boards which provide the clock but this would only be a guess and would really need a logic probe to confirm the fault.
regards Derek
