I had some time yesterday to test the fans and they are working.
I measured the voltages on the 12 pins of power connector. When the projector is in standby mode, I read 3.3V on 2 of them and 3.1V on a third one. Not other voltages were present when I switched on the projector (on/off soft switch).
An EPSON Piranha2 chip (micro controller ?) seems to be powered by one of the 3.3V and is closed to the connector for the switches/LED panel. I suppose it is responsible for turning on the power supply but don't do it for some unknown reason.
I dismounted the block of the power supply. There are in fact 2 modules : one for the main board and one for the lamp. I was a bit surprised by that one:
Is it a high voltage supply ?
On the lamp, I can read 200W 80V:
A small cable is also going from the lamp supply to the main board (for control / status ?).