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2008 pro with ot a and ot b lighting up on logic board

J

j2048b

macrumors 6502a
Original poster
Feb 18, 2009
815
32
Cali
Story:

so i bought (and already had replaced under warranty) sticks of ram from 1800 for memory or someplace like that, about 6 months to 1 yr ago my computer started acting like it would fall asleep, fans would shut off, screens would go black, but the front power light staid on, bright, not flashing (like with a memory issue) just stay bright.... and now neither one of my super drives will open, ive run terminal commands, ive tried what ever i could, and still they wont open, u can hear them try to push open, but they just wont....

I got the memory replaced as a few sticks shows something like melted glue or something on them,

started the mac pro and it worked great for about 3 days, never turned it off, etc...

i plugged it in and finally saw that there were 2 red lights that would light up and they are called OT A and OT B, OVERTEMP is what i believe they are,

i was tryin to set up the usb from dosedude's high sierra and poof computer did the same thing.
i installed smcfan app, had the fans runnin pretty loud and fast and it stayed on until i tried to boot into my usb to install os high sierra, and then ot a and ot b lit up red again, as well as a quick flash from both memory risers.


but from what? what can be overtemping? cpu's? perhaps need some grey goop?


i dunno?

im at a loss right now, finally just unplugged it but im mad because i have yet to find out any info, a few threads ive found and thats it, but nothing that can direct me to what is over temping....

any leads, help, advice, direction... im all for it (i dont live close enough to take it to an apple store that offers any help....
 
If both OT A and OT B come on when you first power up, then it's very likely that you should replace the power supply, as that could be one cause for both LEDs to come on simultaneously.
Your other symptoms (something like a partial shutdown) could be more indications of the same thing. Probably some component inside the power supply is overheating, or just getting intermittent with age.
Apple's service manual can help troubleshoot your issue - but power supply is a good first step, I think.

An Apple store is unlikely to help you with a system that has been obsolete for at least two years. If you want to pursue other help, look for an Apple-authorized service provider (third-party shop)
 
DeltaMac said:
If both OT A and OT B come on when you first power up, then it's very likely that you should replace the power supply, as that could be one cause for both LEDs to come on simultaneously.
Your other symptoms (something like a partial shutdown) could be more indications of the same thing. Probably some component inside the power supply is overheating, or just getting intermittent with age.
Apple's service manual can help troubleshoot your issue - but power supply is a good first step, I think.

An Apple store is unlikely to help you with a system that has been obsolete for at least two years. If you want to pursue other help, look for an Apple-authorized service provider (third-party shop)
Click to expand...

thanks i was wondering if perhaps it could be the psu, im hoping thats all it is, its just odd, but hope it is the answer! thank you for the reply

any chance anyone knows the psu model # needed for this computer?
 
Thanks for the quick reply. Will order one. Not sure how much more I want to investigate with a >10 year old computer. Plus this could be the reason to buy a new one.......
 
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kellen said:
Thanks for the quick reply. Will order one. Not sure how much more I want to investigate with a >10 year old computer. Plus this could be the reason to buy a new one.......
Click to expand...
Yup my thoughts exactly or even follow a youtube video to repurpose this as a server only etc.....
 

Hi guys
I have probably the same problem.
I received from a friend a old mac pro 2008 3.1 aparently broke. He bought a newer iMac and he gave up to that mac pro.
Machine was without graphic card, without hard drive and ram. Processors is dual quad core x5462 2.8ghz. Then i install original apple graphic card nvidia gt 120 in good contdition, 4 gb memory ram
and i try to run El Capitan from 120gb ssd already installed from other apple machine.
Computer start normal, boot with chime sound, i have boot screen with apple logo as well and when the line from logo start to go and grow to boot computer restart suddenly and fans start running very loud.
I force shutdown from start button and try again and againn but with the same issue. In logo bootscreen machine crash and restart and fans go run very fast and loud.
I try to boot from usb installer to see if the issue is from Osx, start boot good, installation start to go for 2,3 min and after computer again restart suddenly and fans go run.
I try everything other memory ram but anyway no issue with ram because when i start pc all red leds from memory bay stop after boot, mean memory ram is ok. I remove bluethoth and wifi, i check all cables and conections
and everything was ok, no issue.
But i notice one problem from begining is a red led open on the motherboard and i know from other mac pro machines 1.1 or 2.1 or even 5.1 when machine run well all leds must be off. But in this machine when i plug power
cable that red led start to be on and never go off. Position for thet red led is between wifi and bluetooth ( see pictures i uploud with red led position). I am confused why that led start to be on when power go in motherboard
I never seen any red led on in other mac pro machines, when i plug power cord, even if computer is off, before i press start button that red run when i plug power cord in machine. From my experience that led can be a issue from
two reasons. First can be a issue from one or both processors or second can be from power supply issue because look to be in connection with power if start to be on when is power in motherboard.
So i remove processors i check in what conditions they are, i check sockets, i clean i reapply thermo paste and i put back. But same issue, nothing chance, same simptoms, same red led on.
Then i decide to replace processors with other two from a old mac pro 1.1. I am not sure exactly number but is 2x 3.0 ghz dual core but same socket 771. Machine start, boot and go finnaly in os very well, all run well i check all specs
i run few applications and after 3,4 min computer stop, restart and fans go again with same issue. In all this time when computer run well that red led was on as weell but flashing exactly like a hard drive led when hard work.
Is clear now the issue is not processors but it is a difference betwen original processors ( x5462)) because with other processors ( 5160 i think) computer go in os run well few minutes and after crash again.
I run apple hardware test AHT, and in first short scan test he didn't find any issue with computer because scan was only around 1,2 min. When i run deep scan after 3,4 min scaning pc crash again.
Now in this moment when i write this, i have to check only power supply but unfortunately i don't have a spare one to do that. If the issue persist after i replace psu, probably i have to replace entire motherboard.
My curuiosity is to ask here if anybody have this issue with mac pro 3.1 and question for you guys is if that red led is normal to be on when power cord is pluged in computer even when is off.
Personal i dont't think so but i need confirmations from somebody else.

Thank you and any answer and advice are very welcome!
 

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