Have had this happen before Lyndon, certain parts of the psu will still be working but that does not mean that all voltage rails are
The pin-outs for an ATX power supply
Pin# Color Function
1 Orange +3.3V DC
2 Orange +3.3V DC
3 Black Ground
4 Red +5V DC
5 Black Ground
6 Red +5V DC
7 Black Ground
8 Gray Power OK
9 Purple +5V standby
10 Yellow +12V DC
(11) Orange(22) +3.3V DC
(11) Brown(22) 3.3V sense
12 Blue -12V DC
13 Black Ground
14 Green PS-ON
15 Black Ground
16 Black Ground
17 Black Ground
18 White -5V DC
19 Red +5V DC
20 Red +5V DC
There is a lot that can fail.