Hello Thanos! Welcome!
If the sad mac came up in 1994, I doubt it would be because of the capacitors. They are now new anyway. Have you checked the RAM sticks one by one, if one is broken, changing its slot may not help.
I guess you have inspected the motherboard for corrosion or bad components.
Is the ROM on a memory stick on a IIcx? It may be the problem?
This is a tricky one for my poor knowledge in hardware. Other members may help you more than I will.
If the sad mac came up in 1994, I doubt it would be because of the capacitors. They are now new anyway. Have you checked the RAM sticks one by one, if one is broken, changing its slot may not help.
I guess you have inspected the motherboard for corrosion or bad components.
Is the ROM on a memory stick on a IIcx? It may be the problem?
This is a tricky one for my poor knowledge in hardware. Other members may help you more than I will.