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New motherboard installed


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#1 scooty43

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Posted 19 March 2018 - 08:25 PM

I replaced my motherboard with one of the exact same. The install went well. All the connections are correct. I triple checked it all. The computer is a Dell optiplex 760 SFF. w/windows 7. The old HD is OK, The power supply seems to be OK. at least it powers up when I hit the reset button. The front panel On/Off button seems to be working because it will shut the machine down when I hold it pressed in. But, that's as far as I can get. When I try to power it up from the front button, the only thing I get is a green blinking #3 diagnostic light that goes out when I release the button. It'll power up when I hit the rear reset button but the front button shows a solid amber light and won't go any further. Total black screen. Maybe I just got a bum board. The sellers description was that it was booting up to BIAS just fine. Any ideas, or should I just walk over to the scrap barrel and drop it in? 



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#2 Guest_Joe C_*

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Posted 19 March 2018 - 08:33 PM

I see.... multiple choice answers for your problem!

Well I would pull the board out, check to see if the heatsink & fan are properly seated on the cpu.

You did clean off all the old thermal paste and applied a new fresh application on the cpu?

With the board out, and on a non-conductive surface, only have the cpu/fan/heatsink, power from the power supply going to the 24 and 4 pin inputs on the board, one memory stick and the keyboard and monitor.

Temp jump out the PWR pins on the front panel pins and see if it'll give you a post screen

 

Is the reset button on the back located on your power supply?

This pc does not show on line that there is supposed to be a reset button in the back.....


Edited by Joe C, 20 March 2018 - 06:21 AM.


#3 Guest_Joe C_*

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Posted 20 March 2018 - 06:13 AM

Dell diagnostic LED fault codes

http://www.dell.com/support/article/us/en/19/sln284978/a-reference-guide-to-the-dell-optiplex-diagnostic-indicators?lang=en



#4 scooty43

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Posted 20 March 2018 - 09:14 AM

Thank you for your response. There is a reset button on the power supply and that's the only way it'll power up. It will not power up at all using the front panel power button. I think I should try a new front power switch assembly. There are also two USB's, the headphone and mic jacks wired into the front power switch assembly. I certainly don't like the way Dell puts these things together. There's such a thing as trying to be too clever.


Edited by hamluis, 20 March 2018 - 10:20 AM.


#5 Guest_Joe C_*

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Posted 20 March 2018 - 10:47 AM

Here is the pin out for the front panel power button and led lights:

Dell_790_pinout.jpg

 

You may need to check that power supply, sounds like that could be an issue. You say it runs when you press the reset on the power supply, and I can't see where an original Dell power supply has that option



#6 OldPhil

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Posted 20 March 2018 - 10:55 AM

Check where you attached the power button, all the power button does is provide a momentary connection of the two pins on the board.  You can unplug the button freom the board then short those pins for a test, if the same thing happens it is not the button.


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#7 scooty43

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Posted 20 March 2018 - 11:04 AM

Here is the pin out for the front panel power button and led lights:

Dell_790_pinout.jpg

 

You may need to check that power supply, sounds like that could be an issue. You say it runs when you press the reset on the power supply, and I can't see where an original Dell power supply has that option

Let me further this issue. When the comp. started to go, the front on/off button wouldn't work at all but pressing the rear reset button powered everything and she booted just fine. At that point the front button showed solid green. After a while, when I pressed the rear reset, the front button showed amber and she wouldn't boot at all, black screen totally. I changed the mother board to no effect. so, that's where I am now? This is a Optiplex 760 SFF. If I said 360, that was my mistake.






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