The work on my Sega Rally 2 has extended out a bit to more of a general Sega Model 3 Step 2.0/2.1 repair exercise.

I've had to reverse engineer quite a bit of stuff to work out what was going on and couldn't find that information anywhere on the internet.

So I thought I'd put together a bit of a guide.

It covers quite a bit of stuff and has photos of what happens when various components fail (basically all ram at this stage). It also includes which ones to actually replace (some of the memory test results actually refer to step 1.5 IC's that don't exist on the step 2.0 board).

I've also done some reverse engineering on the JTAG bus, its role in boot up failures and some insights on how to interpret the boundary scan results.

I've done it as a google doc just to make it easy to update

Happy to take any feedback and/or corrections.