Needing to remove power supply

Question

I have Optiplex 755... I am trying to get power supply out and replace, but it is either stuck or glued...  My computer won't turn on, so I am hoping it is power supply...Thanks for any help....

JOcean · Accepted Answer

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.

bradthetechnut · Accepted Answer

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.

redxps630 · Accepted Answer

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.

redxps630 · Answer

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

happy9999 · Answer

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....

happy9999 · Answer

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....

happy9999 · Answer

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...

bradthetechnut · Answer

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.

redxps630 · Answer

with these old optiplex always do this first: replace cmos battery with a new CR2032 then clear cmos settings via motherboard RTCRST jumper.

redxps630 · Answer

755 DT manual has on psu removal. &#xa0;It says 'Remove the two screws that attach the power supply to the back of the computer chassis.'. &#xa0;Beware that one could mistaken the 2 mounting screws (black) with 4 other screws (for psu fan) on the rear side of psu. &#xa0; &#xa0; &#xa0; &#xa0;

redxps630 · Answer

How to run self-test without the button on the PSU Turn off the computer. Disconnect the power cable from the PSU, and wait for 15 seconds. After 15 seconds, connect the power cable to the computer. The LED light turns on for 3 seconds and then turns off. If the BIST LED turns on, the power supply is delivering power to the computer. If the BIST LED does not turn on or the PSU fan does not spin correctly, the power supply is not delivering power to the computer. Disconnect and reconnect the power cable to computer and try again.

happy9999 · Answer

I only removed the two black screws.... and pushed the tab down.... it is stuck, won't move at all?

bradthetechnut · Answer

Amber light on MB simply means it has power.

Fairly cheap 755 MT PSU on eBay Entirely up to you if you want to replace PSU or not. Was the PC doing a good job before PSU went out, like running Win10? My previous 755 MT with Q9650, 8GB RAM, SSD, flew with Win10. But if it doesn't have certain parts and it ran slow, might be better to invest in newer refurb.

redxps630 · Answer

Possibly because of old age the psu is stuck in chassis by dirt although not fastened by anything. You might have to use a hammer to give it a gentle nudge from the rear end to loosen it up a little bit. Another possibility is that you did not push down the tab far enough. This video shows how easy it should be to remove a DT psu. https://m.youtube.com/watch?v=YGTse-EupHU

happy9999 · Answer

Well I just discovered why it wouldn't come out, there were 4 black screws, it is dark in my office so I didn't see them....So this is a Optiplex 755 mt....So you don't think it is worth ordering another PSU? There is a light on the mobo, not sure if that means it is alright?

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