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The auction says “NOS - "New Old Stock"” If you are in doubt you can send an email to the seller

You can find a 6381-2 replacement chip on ebay for few bucks. I found a seller from poland. Perhaps this seller can program the ic for you.

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

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...

very expensive !! https://www.distrelec.it/it/programmer-usb-porta-parallela-advantech-equipment-labtool-48uxp/p/12596658

I had a similar issue on an M20 mobo. I resolved replacing all the ram ics HM4864P-2. I found 8 bad chips (tested with dramtester) The removal job is not easy and i think is better to use some ic sockets. Davide

I have a PA63 chip but i dont have a programmer... sorry Davide

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 ...

Hello Flavio, please check the mobo jumper config according with the config proposed on the website http://www.z80ne.com/m20/index.php?argument=sections/hack/ramconf/ramconf.inc Davide

Hello, i still waiting for the missing ic to be delivered. I have 2 Olivetti HD-E/10 10mb external hard drives. I hope to have time to check them soon. Davide

It's a great work !! can you send to me as pm to check it ? I really appreciate !! Davide

I forgot welcome to the forum. I have 4 Olivetti M20 to fix. I have 2 motherboard fixed and i am still checking all the 5 1/4 drives. Someone need repairs... Happy to exchange infos, docs and hints with you and the other members of the forum :) Davide

Great Scott !! You have found the missing chip for my board !! Thanks OLI-FIX !! I will set R8 for 1,4 V thought TP1 but how can i set R11 ? Do you have full schematic ? Thanks a lot !! :) Davide

Yes, i have two 128k cards and a 32k. I tried to switch between them in all combinations but no boot

@Flavio Do you have a m20 rev G ? Could you please check the code of the missing ic ? Thanks

Very nice find Chris !! It's a 9+9 pin DIP IC. Unfortunately the photo have not the necessary resolution to read the code in the chip. On the other hand, looking on the D rev. board i can't find any 9+9 IC....

Thank you Chris. I will leave the holder empty. My board is not responding.. It seems to be stuck at boot. Looking with oscilloscope i have some i/o signals on ram and cpu but no output on the monitor (no rhombus) no signal at all i tried to pull out all ics with socket except for cpu- 3 rom...

To better understand my question this is a photo of the ST board

Yes, your board version is BC (the cpu is under the keyboard) not ST. Thanks for the photo :)

Hi all, I have an M20 ST (yes, the one with cpu at center of the board) with an empty socket near the floppy flat cable. Someone can check if it's normal or needs to be filled with a chip ? In case which is the code of the chip ? Thank you in advance Davide