Quote Originally Posted by krifartida View Post
Is there any reason you have isolated this IC as the source of the problem?
I recognize it's an assumption, but I cleared many other causes, like clumsy lyra IC sockets, for example (changed with new better sockets).
And if I can fall in electronic lingo, the CPU /RST signal is driven by this IC, through the two open-collector inverter gates of the 7405 you see in the second photo. And another hint to me is the faded away marking : overheating can conduces to such discoloration. And at last, I like to understand what I see : even if the source isn't here, an unmarked IC titillates my brain

I will try to get the schematics to you ASAP.
It will be great ! Thanks you !

Best regards,