Easiest diagnostics to do on the S7s is to play follow the clock. You'll need a scope for that and it's an art rather than a science - sometimes, trouble later on down the chain will disrupt the startup of the first chip, so nothing is seen consistently anywhere.
The chips are laid out in banks of three and there are two heartbeat signals one going beginning to end, the other end to beginning. Its actually pretty easy to chase down the problem with a decent multimeter and some patience. You can home in on the bank of chips that is having the problem and then do some resistance and other tests to further pinpoint the issue. The s9 is VERY similar in its layout and troubleshooting can be done in much the same way using the diagnostic points that are located all over the board. Just be VERY careful not to short a test point to a heatsink or you can kill the whole board rather easily.