Hi,
I got two broken Pismos from my company. They throw them away because repair would be too expensive for such old machines. As I like these oldies but goodies I would like to revitalize them or at least one of them.

This second machine works fine on batteries, but as soon as I connect the AC Adaptor, it immediately shuts down. Starting with a connected AC Adaptor is not possible, batteries aren't charged. Using the reset procedure (reset button on back) and zapping PRAM didn't change anything.

Due to the symptoms I replaced the Soundcard with one I bought from eBay, but nothing changed and the machine still shuts down on connection with AC Adaptor. I also replaced before and after this replacement the AC Adaptor with a guaranteed working, but without any effort and same results.

Does changing the power supply card, the next step in the service manuals, make sense with these symptoms or might be another part responsible for problems like these?
Thanks

Make sure to test it with the PRAM battery unplugged.

Next I would try a new PMU charger board. After that it'll be the logic board.

Just my follow-up for anyone who has a similar problem:

I replaced the power supply card and this machine is working now without any limitations.
Next step was overclocking from 400 to 500 MHz using the "Magic pencil" method for testing, which was also successful, and replacing the original hard disk with a cheap used 7200rpm drive from eBay.

Machine is now very snappy.

Thanks.

Happy to hear you have it up and running, one thing to remember is that faster hard drive results in more heat and less battery life, if you keep it plugged in, it probably won't matter much, just the right side of your keyboard will keep you fingers warm during the winter months!