Greetings from Arizona.
I am currently following in the footsteps of Scott Keen, who built a
PB 540c Picture Frame. On his site he mentions that with help from Apple Fritter members he built a " a momentary switch (press button to close, release to open) to the ADB port which shorts pins 2 and 4 on the ADB" that allows him to turn the PB on and off. Currently I am doing this by plugging and unplugging the AC Adapter.
I emailed Scott and he was very helpful, but mentioned that is has been some time since he built the Picture Frame.
I have very little experience with electronics, and while I can find sources for momentary switches as well as a ADB diagram I understand how to build the switch. Please any help is appreciated. I really am over my head when it comes to making this switch.