mac pro 5,1 shuts down

[tracer1]

This is on my other 5,1 that only sees windows 10 on bootcamp ( my wife uses it, not a OS X fan). This mac hasn't been touched for about a year and is only used for msn.com & email. If my memory serves me correctly it's has Lion on it but again haven't checked. It's running 8gigs of memory & 1TB hdd. Video card is a radeon 7970.
Now for the problem.....it shuts itself off within 30mins or so of inactivity. As long as you're using it, it will run flawlessly. Only shuts down with no activity. Just started happening last couple of days. Mac is spotless inside & out. Nothing, and I mean nothing has been changed in a year or so. I did throw the nvidia 120 back in it to see if it was the card but does the same thing. I know someone will say "PS" but will run all day in use, so would amaze me it that's what it is. Any one had this problem & found the problem?

 

[tracer1]

WOW.....no one knows. Anyway, update on this. Monitor goes to sleep after 10 minutes. 10 minutes later, mac turns off, no fading light. Changed video card, memory, will change hdd later today. Starting to look pretty bad now.

 

[pat500000]

set your energy saving option to always on.

 

[tracer1]

Well, hoping I'm not speaking to soon. Wife turned it on around 7-8am, just came into the room (5ish pm) & lo & behold it was on. Touched the space bar & it woke as it always have. I had changed the video card & memory early yesterday & it cut off 4 or 5 times after that. Guess it's time for the Twilight Zone theme song? Will post if it goes crazy again soon.
Thanks pat5000000 for the reply. Hadn't got to that one yet.

 

[Auggie]

Read my post and my travails with similar issue. It started off just like yours: shutting down after going into deep sleep (computer sleep), but nothing else.

Gradually over the ensuing weeks, it started shutting down during intense, prolonged disk activity. No warning. Eventually it became completely unusable as it could crash during boot up, right after booting to desktop, or any time thereafter, without doing anything on it.

Apple replaced the mainboard after first replacing the power supply. It fixed the vast majority of the problem... but it does still shutdown sometime during prolonged deep sleep (like after 5 hours or more in deep sleep).

Did some limited troubleshooting but now I don't think it even goes into deep sleep at all; I wake up in the morning or come home at the end of the day and the computer is not in deep sleep.

It's otherwise completely usable and trouble-free so I haven't devoted much effort into further testing, but I eventually must get to that because my warranty for the main board replacement is 90 days...

 

[Auggie]

UPDATE: Well, me spoketh too soon. Just updated to the latest beta this afternoon and now it finally does seem to go into deep sleep (I think it stopped going into deep sleep when the previous beta was installed). And eventually shuts down. It happened twice this evening already while I was nearby. My next step is to boot into one of the older OS X's on the other drives, either Yosemite or El Capitan, and see if it both goes into deep sleep and if it shuts down sometime during deep sleep.

 

[tracer1]

Now that you mention it I just upgraded mine also. And it shut down again this morning, so I guess I spoke too soon on it resolving itself. However mine never went into sleep mode, would just shut down before it went to sleep, just after the monitor went to sleep. No intense disk activity before or after this started happening. As I said this was happening in bootcamp, so I will go back to the OS X & see if does it on Sierra or just Windows 10.