Sinumerik 840D

Dear All

During Booting, RAM check stops say after 28MB and does not get over, sometimes it further contiunes say upto 80MB and stops , after some time, screen changes to press Shift-Tab for Boot Options and nothing happens further

When RAM check stops then sometimes if we press keys like 1,2,3, input etc then RAM check gets over and booting gets over

We have cleaned PCU 50.3 thoroughly and there is no dust.

Kindly advice

Warm Regards,

M. Rishikesh