Exidy circus prom - solved

[vernimark]

After some weeks i could identify the problem of my circus board. The symptoms indicate a problem in the "man" circuit but in the end of the day the PROM in position A8 has gone.
It is a MMI6341-1 512x8 prom. The first 12 pins (left part) are just like a 2716 but I m confused how to adapt the right part; so i m here to ask you:
- can you help me to make an adapter fore a more common eprom?
- or is there someone can burn something compatible or has a spare for me?
Thank you...

[vernimark]

this is the PROM pinout

512*8
   +------+
A7 |1   24| Vcc
A6 |2   23| A8
A5 |3   22| NC
A4 |4   21| CE1/
A3 |5   20| CE2/
A2 |6   19| CE3
A1 |7   18| CE4
A0 |8   17| D7
D0 |9   16| D6
D1 |10  15| D5
D2 |11  14| D4
GND|12  13| D3
   +------+

I can see some NOS are available; can anyone burn them?

it seems to be compatible with 74S474, just for your info.

[philmurr]

It looks to be an equivalent PROM to what's used in Williams games as decoders (7641).

There are a lot of write-ups on how to use EPROMs in their place, http://arcarc.xmission.com/Tech/Replacing%20Williams%20Decoder%20chip%20with%20a%202732%20EPROM/Replacing%20Williams%20Decoder%20chip%20with%20a%202732%20EPROM.htm and this should work for Circus too.

Failing that, I can programme them, and have some blanks, but getting one to you won't be cheap.

[vernimark]

yes seems 7641 are compatible. thank you for the link!

[vernimark]

I can see those PROMs are compatible with 74S474 too
I'm lucky, my Dataman 48UXP can program them

http://www.dataman.com/dataman-48uxp-universal-programmer.html
http://www.dataman.com/downloads/dl/file/id/249/product/24/dataman_48xp_48uxp_device_list.pdf

 

[vernimark]

Done,
in few seconds and euros I could reprogram the game,
thank you for the support!

[vernimark]

this is the link to the topic with the game problems, including the last one (freezing) due to the faulty PROM

https://www.dragonslairfans.com/smfor/index.php?topic=6858.0

[level42]

Great work man !!