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Posted March 13th, 2023 19:00
A bad PSU can still spin the fans. Blinking amber power light can mean bad PSU.
There is a Dell article on BIST test without test button, but since this time I was looking for it, I couldn't find it. Go figure. : )>
As for PSU removal, I never had to remove one from a 755. From this link, Optiplex 755 documentation, find the manual that's for the form factor/size 755 you have. It's not said yet what size you have.
1065
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Posted March 14th, 2023 12:00
that makes sense why your psu would not budge before. MT can use any standard ATX power supply, if you have another working ATX desktop you can borrow its psu to test the 755.
736
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Posted March 12th, 2023 20:00
You can do a psu bist test to determine whether psu is dead or good before removing and replacing it.
700 series MT or DT case have a slightly raised retention tab (a tab with a blue tip in MT) on chassis floor that needs to be pressed down to help release psu after psu mounting screws are removed.
DT
714
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Posted March 13th, 2023 09:00
I removed the screws and pushed down on the tab, but it won't even move even a little... I have removed several PSUs, before, never had any problems... This one won't even move slightly. I thought maybe I needed to remove something else... This computer doesn't have a bist....
710
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Posted March 13th, 2023 11:00
Well I couldn't get the PSU out, I decided to check it with wires on black and green , and fan started running, so I figured PSU was good...hooked everything back up and fan would not start?? When I turn on, "nput not found", comes up on monitor....Now I have no clue... Anyone have any other things to try? When I turn computer on, I get a flashing amber light....Help needed....Thanks to all that has replied....
696
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Posted March 13th, 2023 19:00
I think it is DT, because the others had different size PSU and one with 4 screws, this only had two, and that is what mine has... Why would my psu run by putting those two wires, black and green, but when I plugged it back into mobo, fan wouldnt run? Do you think it might be mobo? Thanks for info...
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Posted March 13th, 2023 20:00
Solid amber light can mean bad MB and you said amber light was blinking. So far we've been limited to the amber power light being the diagnostics. All that was said in opening post was that PC wouldn't turn on. Does that also mean no lights at the time?
So, you're probably right about the PSU. Another way to verify: PSU Testers on Amazon
If you have a full size 5.25" DVD drive, then you have the DT. If it has the slim DVD drive, then you have the SFF.
I used to have a 755 MT. Just to remove the heatsink fan housing, I had to carefully cut off a tab (near the MB) with a Dremel. I can't recommend cutting tabs, but can give a hint if you're still having trouble removing PSU in spite of answers and manual.
684
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Posted March 14th, 2023 04:00
with these old optiplex always do this first: replace cmos battery with a new CR2032 then clear cmos settings via motherboard RTCRST jumper.
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Posted March 14th, 2023 04:00
755 DT manual has on psu removal. It says “Remove the two screws that attach the power supply to the back of the computer chassis.”. Beware that one could mistaken the 2 mounting screws (black) with 4 other screws (for psu fan) on the rear side of psu.
JOcean
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Posted March 12th, 2023 19:00
You did not mention the form factor of your system. But generally there is a latch that must be pressed to release the PSU. You should see it at the back and bottom of the PSU next to the case and no Dell does not glue in the PSU.
I am not a Dell employee...I am forum volunteer
Serious work on an E5430 and constantly building and working on an i5-6500 Desktop