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Optiplex 790 PSU
Just got my Optiplex 790 Mini tower I5, 8gb ram, 1tb hd. Connected everything and the screen is flickering and there is a thumping sound from the speakers when it boots. I booted from an Acronis bootable cd and it works fine. Went back to boot from the hd and problem comes back. Put a cd in the optical drive and the system operates normally. Open the cd tray and the problem comes back. As long as the cd is spinning, the system runs fine. When the cd spins down after a time, the problem comes back.
I am thinking maybe the psu is going bad. I measure 12v and 5v and 3.3v and there is no difference when it is having the problem or when it is running normal.
Does this 265w Dell psu have a normal ATX motherboard connector or is is it something special from Dell?
shesagordie
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July 7th, 2015 14:00
jay1047
Yes, the OptiPlex 790 MT, supports a standard ATX power supply, with either a 24-pin, or a 20+4-pin motherboard power connector.
Bev.
jay1047
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July 8th, 2015 14:00
Thanks
shesagordie
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July 8th, 2015 16:00
jay1047
You are welcome.
Bev.
speedstep
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July 9th, 2015 09:00
ATX is not sufficient. You need an EPS 12V 2.92 power supply. Especially with Sandy Bridge and Haswell based processors.
Corsair CS750M is recommended replacement for Dells that can use a standard power supply.
http://www.amazon.com/Corsair-Modular-Efficient-Supply-CS750M/dp/B00GH9NA0A
You need to see what the COMBINED MAX is. For Dell its 150-170W on the 3.3v/5v rails. Dell Also Specs 4A on the +5vsb rail. This is due to that being added as 4A to 6A in the revised EPS Spec.
CS750M +3.3V@25A, +5V@25A, +12V@62.5A, -12V@0.8A, +5VSB@3.0A
Power supplies are not static 12v only systems.
The corsair CS750M is needed because a power supply that works needs 150 -170w on the 3.3v/5v rails,375W or more on the 12v rails, and 15 to 20w on the +5VSB 3A- 4A. 500W supplys have 100 to 130w on the 5v rails which is insufficient.
EPS12v 2.92 is REQUIRED not optional. The actual Size of the CS750M is also a factor.
Dell power supplies are EPS12V and provide 20W on +5VSB with
150W on the 3.3v 5v rails and 500W on the 12v rails.
This is a 525W dell supply. If you add up all the maximums its 670W.
500W is TOO SMALL
jay1047
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July 12th, 2015 19:00
The PSU is only 265W. The system is a stock 790. Why would I need such a larger PSU?