How to diagnose shutdowns after ~1 minute?

Fishlegs

Junior Member
Sep 18, 2019
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Barebone: Shuttle K48
CPU: Intel Pentium E5300
Cooler: Stock Intel from box
No overlocking, CMOS and BIOS reset to defaults

This PC has been running fine for many _many_ years, until suddenly last week it had a freeze and failed to reboot. I suspected (hoped) it was just a RAM failure, as it booted briefly with 1 stick but failed to boot with both sticks. So I bought new RAM for it (2* 1GB DDR2-666), and now it reliably tries to boot but shuts down suddenly after about 1 minute. I have removed all USB devices, all SATA and IDE devices and am trying to boot from USB stick (as I hope that's simpler). Behaviour is same whether booting from SATA SSD or USB stick, whether case is open (lots of air) or closed, whether fans are on "smart" or "full". CPU heatsink feels normal, orange "945" chipset heatsink feels quite warm but ok, lots of air coming through both CPU fan and case fan. BIOS reports CPU at 49 degrees C and is happy to remain in BIOS for a long time without shutting down, but when really booting it never lasts more than about a minute. How can I diagnose whether it really is something overheating or some mainboard component which has died? Or maybe a problem with the power supply (which was new about 2 years ago)?

There have been no CPU or cooler changes, no transportation, all connections are good and memtest is good (at least until shutdown). Unfortunately I don't have the luxury of spare mainboards, spare CPUs or spare PSUs to test things with, but the RAM is brand new and the USB stick works fine in other PCs. It would be great to know if it's the CPU/mainboard telling the PSU to shut down, or the PSU just shutting down by itself - how can I tell this?
 

daveybrat

Elite Member
Super Moderator
Jan 31, 2000
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Due to it's age, have you inspected all of the capacitors on the motherboard? Are any of them bulging or puffed looking on the tops?
 

Fishlegs

Junior Member
Sep 18, 2019
2
0
6
I've only looked at the _upper_ side of the mainboard, as the board has never been taken out of its case. I've carefully vacuumed the dust out and looked for obvious signs of damage - at least on the upper side there are no bulging components and no signs of heat damage, no scorch marks and all the capacitors look ok (at least to my eyes).