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Apple Mac Pro desktop (2010) logic board resetting. Only power-on LED and a red LED on logic board are on.

I have an acute problem of my Apple Mac Pro desktop computer. On plugging in only its power-on LED and a red LED on its logic board comes on and that is it. No booting up. Please help me.

Mac Pro, OS X Mountain Lion (10.8.2)

Posted on Jan 20, 2015 11:32 PM

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Posted on Jan 21, 2015 7:12 AM

There should be an SMC reset button on the backboard that you can unplug, hold for 10 seconds and then plug back in to try and get a response. You should also try reseating the RAM sticks if you're seeing a red LED signal.

7 replies

Jan 21, 2015 7:24 AM in response to pfsaphoto

Because of the way you phrased your description, I must respond to some things you said:


The Mac Pro 2010 model does not come on automatically when power is applied. It requires a press of the Power-on button on the front of the chassis.


Most debugging for such fundamental problems is done by removing everything that is in a slot, including all drives, the graphics card, and all the RAM. If the fans come on and the power button blinks, that indicates not enough RAM to start up (but processor, Busses, and ROM are working).


The button battery behind the graphics card slot measures a shade over 3 Volts when new, and if it is substantially spent, your Mac will not start up. The battery holder is delicate, try not to break it. If you choose not to remove it, measure with the AC power cord removed (or you are measuring the always-on power supply).

Jan 21, 2015 8:03 PM in response to Grant Bennet-Alder

I rephrase my problem. Once I plug in my computer in socket and switch on wall power buttons, the power-on LED and a red LED which I can see through front grill of the CPU, located on the logic/mother board, comes on before I touch the CPU power-on button. No fans, display and keyboard working. If I press the power-on button or touch a key on keyboard, nothing happens. I have checked my hard disk, processors, graphics card and optical drive with another similar CPU unit. All are perfectly working. If SMC resetting is needed, how can I do that. There is no button for this purpose. However, there are some markings on the logic board with SMC written on them. I have tried different thumb rule operations like removing all peripherals then switching on. Replacement of 3 Volts battery etc. etc. So far no success. Problem is persisting with a lot of frustration

Jan 25, 2015 8:43 AM in response to pfsaphoto

this is the official, one size fits all version:


Intel-based Macs: Resetting the System Management Controller (SMC) - Apple Support


Mac Pro users tend to use a slightly modified version for best results:


Remove AC power cord

Press and hold the power-on button for a quarter minute to completely discharge the power capacitors in the power supply

Restore the AC power cord

wait a quarter minute for "always-on" power to settle

Press the power on button

Jul 3, 2015 6:12 AM in response to pfsaphoto

Hello; this may be a bit late, and perhaps you've already diagnosed your problem, but in my recent experiences [with a Mac Pro 5,1] I've also had to deal with back-board LEDs glowing -- and so I produced the image/annotation diagram included below to help me trouble-shoot issues.


If you look closely at your right-hand photo (jan 26 2015 photo with red led showing), you'll see that the red dot is almost level with the TOP of the UPPER fan assembly (you can barely see the upper fan's outline in the above photo) -- leading one to speculate that you may be seeing the "PSU PWROK" (Power Supply Unit [not]PWROK) or an Over Temperature flag on one of the CPU's. If you open the case and peer inside you can directly map the LED you're seeing to the image/annotation below.


User uploaded file

Apple Mac Pro desktop (2010) logic board resetting. Only power-on LED and a red LED on logic board are on.

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