Re: Turns on briefly and then stops - doesn't post.
more likely issue is with your 390 and not psu replacement. usually these psu are plug and play, and all you need is to connect 24 pin motherboard ATX and 4 pin cpu. can your 390 still POST now by using the Dell stock 275w psu?
The system works just fine with the old PSU - the new power supply works, just not with this 390. All the connectors are correct and you're right, I'm totally used to power supplies being plug n play but so far this isn't happening with this machine. I don't really understand the electrical components and their role in preventing this from powering up. I'm hoping that a different power supply would work if only I could understand what the true requirements are. I have the specs for the machine but I don't know enough to judge. Thanks for responding so quickly.
The only thing I can think of is if the new PSU gypped on 3.3v/5.5v rails. Aftermarket PSU's often boast more power, but won't work if those rails are skimped on as compared to Dell OEM. This is more notable if you're using a GPU card.
If you are using a GPU card, does the 390 boot up without it on the new PSU? I imagine eGPU is being used due to 500w PSU upgrade.
What brand of PSU is being tried in the 390? Never had any complaints about EVGA BR.
As long as the 390 works with the original PSU, that also suggests no eGPU being used, which would make me a little lost. But if you are using an eGPU, we can clear up the power requirements.
I do have a gpu that I want to install that requires 375w but I haven't installed it. I have one more test to try for this psu since I have 3 exact Optiplex 390 MTs - I will try this psu in one of the other machines to see if this machine is faulty. I appreciate your help and I'll letcha know what happens.
Remember what I said about certain power rails? The only thing I can think of is if the new PSU gypped on 3.3v/5.5v rails. Aftermarket PSU's often boast more power, but won't work if those rails are skimped on as compared to Dell OEM. This is more notable if you're using a GPU card.
If it's not those rails, then it is something in the 390, but don't know what it is.
if the 390 does not power on using new psu but works with old psu, I can only imagine there is some bent pin in motherboard ATX socket that is incompatible with new psu, but since the old psu was intimately involved with this pin warp it somehow was still able to provide good electrical contact and work.
The 500w psu works great in another machine so something is faulty in this 390 I've been working on - it WAS plug n play - yeah! Thanks to redxps630 for pointing me back to the 390. On another note, what could cause the bad 390 to reject the psu? Not critical to know, just curious.
I should have disclosed earlier that there was a storm that shut down the machine and it didn't work at all for a while. After letting it sit for a month, I tried it again and it booted just fine - obviously not well enough. I had reset the BIOS and all that stuff and had thought that maybe the onboard graphics was fried so I had another gpu that required 375w so I bought the new power supply (because that could have been faulty too). A convoluted tale, I know........thanks for all the insights and leading me in the right direction. I understand very little about "rails" and their requirements and I'll keep an eye out for malfunctions when I plug in the gpu. Got my fingers crossed that the 2nd machine keeps working!
redxps630
9 Legend
•
15.4K Posts
1
January 20th, 2022 12:00
Re: Turns on briefly and then stops - doesn't post.
more likely issue is with your 390 and not psu replacement. usually these psu are plug and play, and all you need is to connect 24 pin motherboard ATX and 4 pin cpu. can your 390 still POST now by using the Dell stock 275w psu?
Bisquick
5 Posts
0
January 20th, 2022 13:00
The system works just fine with the old PSU - the new power supply works, just not with this 390. All the connectors are correct and you're right, I'm totally used to power supplies being plug n play but so far this isn't happening with this machine. I don't really understand the electrical components and their role in preventing this from powering up. I'm hoping that a different power supply would work if only I could understand what the true requirements are. I have the specs for the machine but I don't know enough to judge. Thanks for responding so quickly.
bradthetechnut
7 Technologist
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9.4K Posts
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January 20th, 2022 17:00
The only thing I can think of is if the new PSU gypped on 3.3v/5.5v rails. Aftermarket PSU's often boast more power, but won't work if those rails are skimped on as compared to Dell OEM. This is more notable if you're using a GPU card.
If you are using a GPU card, does the 390 boot up without it on the new PSU? I imagine eGPU is being used due to 500w PSU upgrade.
What brand of PSU is being tried in the 390? Never had any complaints about EVGA BR.
EVGA BR 500w PSU
EVGA BR 700w PSU I don't know if you're using an eGPU or it's model, or how many watts it is, so I listed a couple of different PSU's.
redxps630
9 Legend
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15.4K Posts
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January 20th, 2022 19:00
Re: if only I could understand what the true requirements are
the only requirements are 24 pin ATX and 4 pin cpu per ATX standard. any decent ATX psu should be good. try a small non-Dell psu to see it helps.
bradthetechnut
7 Technologist
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9.4K Posts
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January 20th, 2022 20:00
@Bisquick
As long as the 390 works with the original PSU, that also suggests no eGPU being used, which would make me a little lost. But if you are using an eGPU, we can clear up the power requirements.
Bisquick
5 Posts
0
January 21st, 2022 07:00
I do have a gpu that I want to install that requires 375w but I haven't installed it. I have one more test to try for this psu since I have 3 exact Optiplex 390 MTs - I will try this psu in one of the other machines to see if this machine is faulty. I appreciate your help and I'll letcha know what happens.
bradthetechnut
7 Technologist
•
9.4K Posts
0
January 21st, 2022 10:00
Remember what I said about certain power rails? The only thing I can think of is if the new PSU gypped on 3.3v/5.5v rails. Aftermarket PSU's often boast more power, but won't work if those rails are skimped on as compared to Dell OEM. This is more notable if you're using a GPU card.
If it's not those rails, then it is something in the 390, but don't know what it is.
redxps630
9 Legend
•
15.4K Posts
0
January 21st, 2022 10:00
Re: The system works just fine with the old PSU
if the 390 does not power on using new psu but works with old psu, I can only imagine there is some bent pin in motherboard ATX socket that is incompatible with new psu, but since the old psu was intimately involved with this pin warp it somehow was still able to provide good electrical contact and work.
Bisquick
5 Posts
0
January 21st, 2022 10:00
The 500w psu works great in another machine so something is faulty in this 390 I've been working on - it WAS plug n play - yeah! Thanks to redxps630 for pointing me back to the 390. On another note, what could cause the bad 390 to reject the psu? Not critical to know, just curious.
Bisquick
5 Posts
0
January 21st, 2022 11:00
I should have disclosed earlier that there was a storm that shut down the machine and it didn't work at all for a while. After letting it sit for a month, I tried it again and it booted just fine - obviously not well enough. I had reset the BIOS and all that stuff and had thought that maybe the onboard graphics was fried so I had another gpu that required 375w so I bought the new power supply (because that could have been faulty too). A convoluted tale, I know........thanks for all the insights and leading me in the right direction. I understand very little about "rails" and their requirements and I'll keep an eye out for malfunctions when I plug in the gpu. Got my fingers crossed that the 2nd machine keeps working!