OMG, I forgot about that. DOH!
Do you hear the fan turn on in the power supply when you turn on the Mac? I notice in your picture that the speaker is connected. Hmmm... I can't think of many things left to try except inserting a ROM SIMM.
The more I think about this, the more I realize how rusty I've gotten. Maybe 6100s DO need ROM SIMMs. I'm not completely sure anymore. For some reason before, I was absolutely positive that they didn't need them. Now we need to get to the bottom of this.