Olivettti M20 ST missing chip

[Dwight Elvey]

Here is a schematic and hardware manual that Davide found for me:

http://www.z80ne.com/m20/sections/manuals/hw2.pdf

As Davide said to me it is hard to follow but it was what I used to bring up my understanding of the M20's hardware and addressing.
Dwight

 

[one1test]

Now i have the missing chip for this board.
I replaced all the 16 ram ic (i found 6 bad chips).
Actually i have no clock signals on cpu and video ic (MC6845) but i can see 12mhz and 16 mhz measured on the oscillator quartz.
Anyone have the clock generator schematics ? @OLI-FIX do you have it ?
Thanks to all
Davide

 

[OLI-FIX]

12MHz clock path is still incomplete in PDF. 16MHz is more detailed. Did you check the pdf already?

 

[one1test]

I only realized now that the pdf have more pages. I saw the first page only.
Yes, it was a great help to me. I found no signal on U108 but 12mhz on the quartz. I solved by replacing the jumper.
Same thing about the cpu clock signal: I replaced the AA jumper. I also found some bad contacts on the cpu socket which I will replace shortly

 

[one1test]

In the meantime i started to check the floppy drives.
They seems to be not working (except one).
Anyone have a schema or a procedure to check by oscillocope the raw data ?
@OLI-FIX yes, i found the floppy connector pinout from pdf. I will try to start from here