Advanced Genesis 1 repair (Mega Drive is Mega fried)

Hey all,
In my incredible stubbornness I like to fix every system I've ever come across. I have only two consoles I haven't repaired from my parts bin and one of them is a Genesis model 1 VA 7. For any sane person it's probably not worth repairing, but I would really like to learn from this one and feel the pride of bringing it back to life after destroying it nearly 10 years ago.

History: the first part of the system that was destroyed was the op amp audio stage followed by the video analog stage. Both are primarily board damage and trace damage that shouldn't actually short or effect the main CPU/ASICs

What happened next was bad though: a long long time ago in a galaxy far far away I shorted the clock input to the 68K. It shorted so bad it actually fried the clock output from the ASIC (315-5487-01). After that I used this as a salvage machine and gutted SRAM and passives...

I've since replaced all the passive components and what appears to be a working 68k processor. I replaced the SRAM with questionable ICs... Might have to try some others. I don't have a 7 megahertz Crystal on hand so I'm I'm feeding the 68k a 6mhz TTL can externally.

What works and what doesnt: I get a power light on the z80 which is probably fine. ASIC outputs a steady pulse for the subcarrier clock and for the Sync. Oscilloscope tests show that those are fine which leads me to believe the internal clock divider is probably okay.

However, RGB produces nothing on the output of the ASIC and the audio L and R are half of VCC or 2.5 volts. I strongly suspect the SRAM but before I go replacing it is there something else I can check?
Basically, I'm curious to learn more about the repair flow for these systems beyond simple analog and capacitor repairs. It would be cool to learn from this poor beast.

 

I finally repaired this beast and it was an epic journey. I created a detailed repair log to share with the world so that others may fix their systems too!
https://segasonicfan.wixsite.com/retro/repair-logs

 

Obligatory why didn't you just buy a new one.

Seriously, this is awesome work. Learning to repair these machine when there are "plenty" of spare units around is a great idea. One day the supply of extras will run out. My hands aren't steady enough to solder anymore, I can't even fix my Saturn modchip (sad face) due to my tremors now.
I applaud anyone who actually fixes old hardware. My favorite things to watch online are hopeless devices that are brought back to life through the dedication of true hackers.

 

Thanks for checking it out! Yeah, I agree, these things wont be around forever (already pushing 30+ years old ) I am always making videos of "hopeless" repairs and hacks, you can watch here if you like:
https://www.youtube.com/segasonicfan

oh damn, thats crappy...hey, PM me and Ill help ya out. I can either a) send you the spare knockoff modchips I have or b) Ill fix it for ya for shipping cost.