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Mortal Kombat 2 - memory expansion board (identify parts for service)

juanmiglesias

juanmiglesias

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Pembroke Pines, Florida. Zip code 33027
Hi everyone, I have been going through my old boards, servicing the ones I had pending, which takes me to a Mortal Kombat 2 board.
I have the sound, main, and expansion, but the expansion memory needs work, when bought the seller seems to have misplaced the memory board outside in his shop, and one EPROM rusted over time, overall board needs some work. nothing serious that I can see on the traces.
I just want to buy every single replacement to have it in stock.
Already got:
EPROMs, sockets, caps, and axial resistors.

looking for:
- the 60pin header which seems standard 1inch length
- the 74actq244 seems it has a modern counterpart: https://www.digikey.com/en/products/detail/texas-instruments/SN74ACT244N/375910

Need help with:
The ones I am not knowledgeable about are the SIP resistor and the one highlighted in yellow, I went to Digikey, and filtered 10pin but no 4.7ohms shows.
is my understanding this is a SIP resistor: 9 resistors / 10-pin / 4.7 Ohm.
added a photo of the part. But all I can find is 4.7K, could this be a typo?
Thanks.
MK-2.jpg

mk2-2.jpg
 
Try measuring the resistance between the pins and see what you get, although you may get some misleading readings with other components in circuit. Failing that if you're going to remove it anyway just measure it once off the board.

Also not sure if you are aware but you can swap the main board EPROMS to larger ones and do away with the expansion board completely.
 
tiff_lee said:
Try measuring the resistance between the pins and see what you get, although you may get some misleading readings with other components in circuit. Failing that if you're going to remove it anyway just measure it once off the board.

Also not sure if you are aware but you can swap the main board EPROMS to larger ones and do away with the expansion board completely.
Click to expand...
Oh wow! I was thinking about that,. if it was possible to swap to 27801 eproms, is just writing the 3.1 prog and the roms set and that is it? any guide or tutorial to double check

- btw after realizing my noob moment, I just went and did what you mentioned, 4.7K, so yeah it is a typo, I confirmed the same part in an unaffected area. all of them 4.7K
 
seems I need a new Gal chip and move the resistor (I imagine they address the 8mbit).
 
Thank you, already found the GAL file for the current GAL16V8, ordered the t48 (my current programmers can't do GAL/PAL) so a little nice investment for sure, and ordered some GAL16V8, so I am definitely giving this a try. I will also fix the memory expansion for correct preservation.
I will reach out to the post if I find any obstacles, but so far seems pretty straightforward.
 
I was confused before as well, it must be the way the article is written.
PAL dump is good.

Gal works, but you get gfx errors and eprom errors CRC bad, etc. The GAL is too slow.

You need TIBPAL new and unwritten, these are fast enough.
 
Last edited:
Asure said:
I was confused before as well, it must be the way the article is written.
PAL dump is good.

Gal works, but you get gfx errors and eprom errors CRC bad, etc. The GAL is too slow.

You need TIBPAL new and unwritten, these are fast enough.
Click to expand...
and does the code work for a PAL? because it seems the dump for A-17748 (the 8mibt PAL conversion needs) is targeted for a GAL16V8. are the Jedec code files universal for certain pinouts or actually does work only on the targeted device?. first time messing around with pal/gal so not really sure how they code for them.
I see the article does mention the difference in speed, but that would be for a 4mibt restoration correct?
I am actually modding the 4mibt board to convert it to an 8mibt, hence I do need the A-17748.
this is the link for the Files which does mention the GAL issue, but seems it is only for the A-17480:
https://wiki.pldarchive.co.uk/index.php?title=Mortal_Kombat_II_(T-Unit)

BTW thanks again for all the replies, this is really helpful so I don't mess anything up lol, I know the board works even with the GAL, just that my programmers a t48 and a gq-4x won't do the pal, or at least is not in the list (maybe there is the code to add it), the t48 does write the GALs. So if the A-17748 is good to go as a GAL I am good to go, if not, well I might just try it when it gets here and look for the pal one in the meantime.
 
juanmiglesias said:
are the Jedec code files universal for certain pinouts
Click to expand...
Yes. JED files can go into PAL or GAL. You will require a PAL as the GAL is just not fast enough, and this leads to GFX errors.

This is all optimized for speed, even in the MK2 source code, the floor and shadow sections of code are cache aligned and rely on this to be a super fast operation.
 
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