Hello,

Clive, maybe you are right ... I have free time just to check LPT voltage - it is 3.3v on both PCs ...

I didn't check it before, because using one of the PCs with my bigger CNC machine I didn't have any problems for years !! ...
The same drivers on all machines !! ..

But when using it in another place / room I received the problem with both PCs -

So .....

Machanics is not an isuue ... motors knock on the table :) .. not connected to the machine ...

My plan - to add 6N137 fast opto - as opto and also as logic level 'converter' .. :)

( also I have them on 'stock' :) )

When I finish will write here the results ....

Thank you all of You !!

Emil