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Red light flashes briefly on Mac Pro as I turn on my UPS.

Could anyone here perhaps assist and help me understand why my mid 2010 Mac Pro has a red light that flashes as I turn on my UPS?


It happens very quickly and doesn't stay on, just as i hit power on at the front of the ups and then the red light goes off. I can see it through the front grill of the Mac Pro.


Switching on the Mac works fine and it runs perfectly normal as well.


I opened the machine and tried seeing which light goes on and it's at the top of the motherboard, just under the first harddrive but thins there are so tiny I couldn't see which light it was that flashes and it also happens real quickly. I also couldn't repeat it the second time I turned on the ups.


Should I rather not use this ups? Does anyone know what the reasons are for this happening?

Mac Pro, OS X Mountain Lion (10.8.4), 10 GB RAM,Cranesong,Mytek,LP 9.1.8

Posted on Sep 6, 2013 9:58 AM

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Posted on Sep 6, 2013 2:26 PM

anything else on the same circuit even if on a different outlet?


I assume the UPS is saying there is an overload or you don[t have a proper ground, or could mean a weak battery.

It should also be doing a self test when turned on. And I dont' think turning on and off is the way it should be used, leave it on and protecting your equipment (and you do want a UPS that can handle coax, dsl, rj45) so you filter and protect modems and such.


The one I linked to you also have a front panel with all the various readings you need.

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Sep 6, 2013 2:26 PM in response to Chance Harper

anything else on the same circuit even if on a different outlet?


I assume the UPS is saying there is an overload or you don[t have a proper ground, or could mean a weak battery.

It should also be doing a self test when turned on. And I dont' think turning on and off is the way it should be used, leave it on and protecting your equipment (and you do want a UPS that can handle coax, dsl, rj45) so you filter and protect modems and such.


The one I linked to you also have a front panel with all the various readings you need.

Sep 6, 2013 10:31 AM in response to Chance Harper

So far you have not ID'ed just what make/model and VA/Watts of what you are trying to use, but it should be 900W and 1000VA or above. APC use to be my brand of choice, RS1500 but as they got older swapped out for the below and have a mix of for all equipment and TVs, modem, router and disk drives.


CyberPower UPS

http://www.amazon.com/CyberPower-CP1500PFCLCD-Compatible-1500VA-Tower/dp/B00429N 19W/


As for the red lights being under the hard drives I am not sure where you are pointing to, usually RAM tests and motherboard.


I never ever turn off my UPS, I do once in awhile shutdown the Mac Pro, but the UPS on. Some use a good quality (think $65+) surge protector (not recommended by APC) and turn off peripherals via surge protector. And you could have one for the Mac Pro.


When you turn on the UPS, that by itself should not though cause the Mac to boot or turn on. You are still hitting the power on button, right?

Sep 6, 2013 1:16 PM in response to The hatter

I don't know that the watts or volts spec are but it was sold to me by a place that builds upses and they seem to know what they doing. I will have a look at the specs and report back here soonest.


In the meantime I can confirm that I do still have to switch on the Mac Pro by pressing the metal switch on the front of the Mac before it actually boots up. The red light flashes just as I turn on the ups, which only powers the Mac Pro but does not cause it to switch on.


The ups on the front reads: UPS-1400.

Sep 6, 2013 6:54 PM in response to Chance Harper

Chance Harper wrote:


Could anyone here perhaps assist and help me understand why my mid 2010 Mac Pro has a red light that flashes as I turn on my UPS?


It happens very quickly and doesn't stay on, just as i hit power on at the front of the ups and then the red light goes off. I can see it through the front grill of the Mac Pro...

Since turning on the UPS is equivalent to plugging the Mac Pro into a wall outlet or flipping the switch if the outlet has an on/off switch, what you're seeing is the computer confirming it's got power. To quote from the Mid 2010 Mac Pro Apple Technician Guide:


"2. Attach a known good power cord from a known good AC source to the Mac Pro.

Note: When connecting the Mac Pro to AC power, verify that the LEDs for OVTMP CPUA and OVTMP CPUB briefly flash red (less than 0.5 sec). The LEDs are located under hard drive bay 1 on the backplane board. If they do not illuminate briefly, there is an issue with either the power supply or the backplane board. Generally speaking, power supplies can be affected by issues more than other modules. If you suspect a power supply has failed,verify it in another Mac Pro (Mid 2010), if available, before replacing any modules.

Note: The OVTMP CPUA and OVTMP CPUB LEDs on a properly functioning Mac Pro will also momentarily flash red immediately after the Mac Pro is disconnected from AC power."


So the red light flashing is your Mac telling you it's ready to rumble.😉

Red light flashes briefly on Mac Pro as I turn on my UPS.

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