Genesis II/Mega Drive II - System probe questions

Hey guys -

Would one or more of you guys be kind enough to tell me your approach to walking a Genesis 2 with a probe (or any other console, I suppose) when you know -

1: Power is good
2: Test cart is good/clean
3: Cart slot is clean/reflowed
4: A/V cables and port are good
5: Traces/ICs/caps "look good"

etc...etc...

Basically give me an idea of how you walk it for checking cart/CPU clock/address/data communication, CPU/RAM test, etc. provided that you have already passed the "usual suspects" (like those above) in a given test case.

 

You plug a cart board in, check all traces from it to the 68K CPU (besides the two select strobe signals all other pins will connect to the 68K). After that you check the two extra strobes and they should go to the big ASIC.

If the basic stuff is working you should be able to see at least the TMSS screen. Most times I had to repair a TMSS system which weren't displaying it, was problems between the 68K, it's RAMs and the cart slot. (broken traces or blown chips)

You need to test continuity. Visual inspection is not good enough.