Sega Blast City PSU help

[Francky]

A sign of needing recap on blast cities is struggling to power boards reliably, especially things like a NAOMI. But for example if you have a cps2 board with lots of roms, and struggle to keep 5.0v at the JAMMA edge with the PSU Potentiometer turned up, then it's definitely time to work on the power supply.

My issue is that my low voltage don't let run the CPS2 , i have 3.80V instead of 5V and 3.50V instead of 12V , what could it be ,the round transformer at bottom of the PSU ? it must give the 12V on a wire i think to the PSU card .