Thanks for your Help!
I´m gaining access to a reader (bought one off Ebay today... )
I meassured X1 with my Frequency Counter and the Frequency is 11.963 MHZ +/- 0.001 Mhz (Last Digit keeps flipping between 3 and 4). Seems good so far.
Is the D78C11 in theory replacable?
I got the adequate soldering equipment, but it seems to me that its a Version with a custom Rom mask?http://www.alldatasheet.com/datasheet-p ... 8C11A.html
This is the Datasheet for the "A" Version but the text on my chip says: d78c11G.
In the Datasheet you can see that every Version with a G in its Descriptor got that custom Rom mask. I´m little unsure about that...
Next things to do for me:
-wait until the Reader arrives and read my OP rom
-get an Oscilloscope to have a better look at the clocking signals
With that Oszi i could meassure the output data lines of the D78C11 to see if there is some reasonable activity.
Thats my plan so far...