Heh, been there done that... I've spent an entire day before trying to find an electrical bug.... posted about it on a forum (just to vent not looking for a solution) and someone asked if I worked through the flow chart in the service manual... I grumbled, but did look. Next day I went out and it was something like item #3 on the cart! Took all of 20 minutes to fix.
But yeah, I've learned a LOT from exploratory surgeries on the Supe.