Mini powers off randomly all of a sudden?

[silence2-38554]

Hey all, this is my first post here. The machine in question is a 2006 mini that started it's life with an intel 1.5 Core Solo CPU. I have since swapped the CPU with a 2.0 C2D. It is running 2 gigs of RAM & my MBP's old 250gig HDD. I primarily use this Mini as a living room media machine & it has been running this exact hardware configuration for about a year.

A few nights ago, we were watching a movie (file was stored on an external FW drive) via PLEX, and the machine just shut off about an hour into the movie. When I attempted to re-boot, I got a gray apple logo screen for a few seconds, then nothing. Tried re-booting again, got a gray screen for an even shorter period, then died. After that, the mini would not respond to anything. SMC resets did nothing, it would literally just not do anything at all. No power LED or fans, just a paperweight.

The next day, I tried it with a known good PSU. Everything seemed to be fine after resetting the SMC & PRAM. Strange, I thought. So, I tried it again with my power supply. Fired right up & has not exhibited issues since.

WHAT could be happening? Does this sound like a logic board? Shoddy PSU? Weird software / firmware glitch?? Any help with this would be GREATLY appreciated!!

[jb]

Minis will shut themselves down for self protection should they overheat.
Could explain why it running again after a short period of downtime.
Have you ever taken it apart and cleaned the dust-bunnies out of the fan and innards?

[silence2-38554]

I just pulled it back apart & it's actually squeaky clean inside. Not even a hint of dust, let alone a full bunny! I also don't think It's heat related, as I had pushed the mini way harder than I was at the time it shut down. I am going to replace the PRAM battery this morning, as I know it has never been replaced & it looks like it has been the cause of some other people's no-power issues. I would also like to test the PSU's output with my multi-meter, but I can not seem to find a pin-out of it's plug anywhere online. Could someone please point me to a link that documents which pin is hot, ground, sensor wire, etc?

[silence2-38554]

Okay, I replaced the PRAM battery (the old one measured 3.1v, so not too bad). I also just got out my multimeter & tested the contacts in the plug. 18vdc solid, no fluctuation at all.

The bad news: After putting everything back together from the PRAM battery change, after plugging the mini in, it's power LED came on immediately without me touching the power button..... It was also not producing any video output. After about 30 seconds, it shut down. Okay....I go to power it back up. It goes to the gray apple logo boot screen after a couple seconds, but with no startup chime at all & the power LED is OFF the whole time. After about 20 seconds, shuts off. Power on again, does the same thing for about 10 seconds, shuts off. I repeated this another 5-6 times, each time the mini would get less & less responsive. Now, the mini is once again a paper weight, not responding at all to power on attempts. I checked the power adapter output & it still reads a strong 18v.

My last attempt at troubleshooting this will be to swap the original CPU back into the machine & see what happens then.

After all this, I'm leaning toward the logic board being toast. Sad times. Is anyone on here familiar with the design of these boards? is there a particular component that is notoriously problematic? I'm sure I'm grabbing at straws, seeing as how everything on the board is miniature & surface mounted, but still.... I'm wide open to any other suggestions before I pull the trigger on a new mini & part this poor thing out.

[philiparcario]

If I remember some mini's had cap problems on the logic boards. maybe smithcraft can chime in with an answer.
_________________
2010 Mm 2.4 C2D oem 320gb hdd 8gb ram
2012Mm base 2.5 with 16gb ram diy fusion drive
2012Mm quad with 8gb ram oem 1tb hdd

promise pegasus r6 3x 3tb + 3x 4tb =21tb hdds
lacie little big disk 2x 512gb ssds
synology 2tb disk station

[silence2-38554]

That would be fantastic! smithcraft?

Also, I was testing the power supply a bit more & noticed that I can't get the center pin to do anything. From what I understand, the outer pins are ground, the next set in are 18vdc, and I read somewhere that the center pin is a sensor / remote wire that lets the mini know if it's receiving the correct power. Some other forum mentioned that it should measure 3vdc but I can not get a reading on it at all..... I really hope this does indeed being the fault of the power supply!

[silence2-38554]

Bad news, wasn't the power supply. I had the chance today to test the mini with a known good supply & it did nothing still. I tried swapping the RAM around / booting with one stick at a time, nothing. I swapped the CPU back to the original 1.5CS. nothing. It's fate is sealed. Dead logic board. Now the big question: do I pay to have the logic board replaced or just replace the whole machine with one that's more up to date?

[macmanmacman]

it sounds like the mini has gone to mini heaven i would just upgrade