Had an issue with the motherboard...
Try swapping every component on a socket
--nope--
Let's desoldering ram chips and insert sockets for them. Pictures before, without (both sides) and after
--nope--
Tester many things, thinking : "should be a not enough durable component that has died"... checked every socket, every capacitor.

The xtal died, I tried with no conviction to test with an other (half value but nevermind) it starts... (weird because peripherals have a clock which is twice the cpu ones)

A friend has a 16Mhz xtal to give me (same *old* ref)

And now I have ram on sockets...