lucky9 wrote:Welcome to the forum gregorylock!
Check your BIOS for settings that concern (saving) power. Set all of them to off. If this doesn't do it then I'm with uncle mark. Get a decent power supply.
You might try a cheat code at boot. noacpi comes to mind. Check the wiki. Link is at the top of this page. Use cheatcode in the search box.
I bought the new power supply that was recommended here in this thread, and I also checked all the capacitors. The new power supply is installed and runs much quieter than my old one. However I'm still experiencing the shutdown problem under Linux. Since you brought up the BIOS settings I took a little time and took pictures of it. If you see anything in there that you think I should change let me know. Because I don't... (shruggs)
I see that there are other suggestions in this thread that I have not tried yet. If you guys have any other suggestions to add please add them. I'll try anything eventually. Then I'll report back.