Multiple PSU issues - but only from one wall socket...

[Felixim0]

Recently my Dell Precision T5400 workstation started flashing numbers 1 and 3 on the front of the case, apparently indicating a PSU failure. (https://www.dell.com/support/kbdoc/en-uk/000123890/precision-t3500-t5500-t7500-workstations-diagnostic-lights-and-beep-codes). I tried reconnecting all  the internal wires to the PSU, still the same error code. I replaced the computer with a spare Compaq Presario (HP Compaq Presario S5390FR) so that the user could continue with light web browsing while I diagnosed the Dell Precision. However, the Compaq didn't turn on, and a single LED on the PSU was flashing. 
This lead me to believe the issue must be something to do with the socket on the wall. I tested both computers on other sockets and both worked perfectly. The issue in the original socket is intermittent, and I have no idea what I can actually do to fix this - all other devices (laptop, monitor, printer) all work fine off the socket all the time.

TLDR: Does anyone have any idea what could cause PSU BIOS error codes intermittently , but only when plugged into a specific wall socket? (When that socket works fine for other devices.....)

[The Torrent]

8 minutes ago, Felixim0 said:

Recently my Dell Precision T5400 workstation started flashing numbers 1 and 3 on the front of the case, apparently indicating a PSU failure. (https://www.dell.com/support/kbdoc/en-uk/000123890/precision-t3500-t5500-t7500-workstations-diagnostic-lights-and-beep-codes). I tried reconnecting all  the internal wires to the PSU, still the same error code. I replaced the computer with a spare Compaq Presario (HP Compaq Presario S5390FR) so that the user could continue with light web browsing while I diagnosed the Dell Precision. However, the Compaq didn't turn on, and a single LED on the PSU was flashing. 
This lead me to believe the issue must be something to do with the socket on the wall. I tested both computers on other sockets and both worked perfectly. The issue in the original socket is intermittent, and I have no idea what I can actually do to fix this - all other devices (laptop, monitor, printer) all work fine off the socket all the time.

TLDR: Does anyone have any idea what could cause PSU BIOS error codes intermittently , but only when plugged into a specific wall socket? (When that socket works fine for other devices.....)

Taking a guess, perhaps its some sort of ground issue? Somehow maybe that exact computer refuses to boot without a sufficient ground connection for safety? Check the ground pin on the socket.

[Applefreak]

9 minutes ago, Felixim0 said:

Recently my Dell Precision T5400 workstation started flashing numbers 1 and 3 on the front of the case, apparently indicating a PSU failure. (https://www.dell.com/support/kbdoc/en-uk/000123890/precision-t3500-t5500-t7500-workstations-diagnostic-lights-and-beep-codes). I tried reconnecting all  the internal wires to the PSU, still the same error code. I replaced the computer with a spare Compaq Presario (HP Compaq Presario S5390FR) so that the user could continue with light web browsing while I diagnosed the Dell Precision. However, the Compaq didn't turn on, and a single LED on the PSU was flashing. 
This lead me to believe the issue must be something to do with the socket on the wall. I tested both computers on other sockets and both worked perfectly. The issue in the original socket is intermittent, and I have no idea what I can actually do to fix this - all other devices (laptop, monitor, printer) all work fine off the socket all the time.

TLDR: Does anyone have any idea what could cause PSU BIOS error codes intermittently , but only when plugged into a specific wall socket? (When that socket works fine for other devices.....)

Bad contact maybe on ground on that socket. Can't hurt to check the wiring in the wall if you know what you are doing. To be safe get an electrician to check it out. A better power supply maybe able to compensate for voltage and frequency variations, thus cause less problems. Also check for other devices on the same breaker, there maybe interference by one of them. Microwaves, Fridges that have a freezer unit, AC units etc. are candidates to look out for. My recommendation would be to wire up new wall outlets but check the cables first. If one of them is not shiny brown copper anymore, I'd replace the entire mainline to the breaker panel. Usually this can be done fairly easily by an electrician in under an hour.