***********************WARNING******************
On then Right Off is NOT a PSU issue.
You have a motherboard problem. 
Each was pull from a working CECH-G01.
I have a few good, tested ones.
You can see these fully tested on my YouTube channel as of today 9/3/2023.
The G Model was the Transition from A/B and Has PSU and Outer drive board Disk Drives that work in those backwards compatible PS3 PHAT. 
This has the same Left side Circle Pole Holes to the motherboard.
Both Back and Front Connections are the same. 
The ONLY difference between this PSU APS-231 and APS-226 is a bottom plastic instead of Metal.
I would assume it was to save costs. 
^^^^^^^^^^^^^^^^^^^^^Very Important^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Every PS3 PHAT Model after G is Black with Square Pole holes on the Right Side.
H, K, L, M is Completely different from these APS-231 or APS-226.
Finally, the Last Model P is a Different Black Model PSU ONLY for the P with a Larger Front connection.
NONE of these works on the other.