PSU was fine. Next one is the ARI Board. First as usual tons of reading.
Obligatory Bob Roberts Link
Page 32 for the schema, page 33 for the parts list.
ARI boards handle 5V regulation for game PCB and audio amnplifier. So measure the regulated 5V vs GND VDC.
Since I`m facing psu issues first, I`m taking a closer look to
C1, 470uF, 25V
and of course 5V vs GND
pin5,6 vs GND
pin1,4 vs GND
Additon : just found a good pic