I have an associate with a dead Plus. No video and a strange "rattling sound" when turned on. (Attached is the rattling sound. I could only upload it to AppleFritter by chaning the extention to "jpg." But this will prevent you from hearing the sound. So please download the file via CONTROL-CLICK and then change the "jpg" part to "mp4" or it won't play in OS X.)
To continue the list of problems...
No bad smells. No burn marks on analog board upon examination. Putting the logic board from that bad Plus into a known-good Plus doesn't boot the known-good Plus (i.e., logic board bad). But putting a known good logic board into the bad Plus doesn't fix the bad Plus either (i.e., analog board bad). Voltage levels as taken at the floppy drive connector are as follows:
+1.3V (instead of normal +5V)
+7.5V (instead of normal +12V)
-7.5V (instead of normal -7.5V)
Thoughts and insights would be appreciated.