PM 5500: Frequently soft pwr only starts drives, monitor init - no chime, no boot

[estravolta]

I recently got a Power Macintosh 5500/225. For a few days when I'd power it on, it would come on no problem. After installing an IDE-to-CF adapter it started getting finicky and when I would apply soft power I could hear power go to the display, and the CD/floppy drive would make noise, fans on, etc. but no startup chime and it wouldn't boot.

Other details:
* This happens with and without the OEM spinning HDD
* Boots more frequently with the OEM HDD but has booted successfully with the IDE-to-CF card
* PRAM battery is dead
* I've tried booting without any expansion cards, same situation
* When operational, the screen with enlarge slightly (maybe 1mm on all sides) when clicking on certain items (like when I open Mac HD from the Desktop)
* Multiple keyboards tried

Any ideas? TIA

 

[wottle]

I believe no PRAM battery is better than a dead PRAM. I don't believe the 5500 requires a PRAM battery to boot (at least mine doesn't). However, the symptoms feel like a dying power supply. Sending wrong/fluctuating voltages to the analog board might explain the enlarging of the image during certain tasks...

 

[cheesestraws]

Agreed; I'd be looking suspiciously at the power supply to start with with these symptoms.