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Oh, ill just stick with the original then haha Yeah I've read that all over different forums, I've only got the machine as it was my neighbour's sons, so thought I'd give it a go trying to fix it up as project. Hopefully it'll be an easy fix if not then it'll be getting stripped down

hello and welcome

Fruit machine security hack for mpu4 early crests. Rids CHECKSUM. CHARACTER. so if you buy a collectors machine of this era and its missing the program card you can now make it up as im showing you how to remove the checksum on some early mid 80's machines the comparison is between SMASH N GRAB (BREAk N TAKE) and CRACK THE NUT (2p clone) now the 2p clone was already hacked by the company to run with no checksum and no character. i found the comparison after weeks of copying and pasting to see what things do and saw that if you change "26" to "20" it hacks the machine. but which 26 to 20 as the program has loads. so i see it has "C501" before it. look for the C501 normally in the bottom to mid part of PROM 1. then if it has a 26 after it change it to 20 make sure you have the original roms backed up incase this dont work. as i think later machines they moved it, thats why i had to say no to some people wanting me to hack their machines (from peter on facebook) UPDATE To clarify what that does buddy.. what you did there was alter the way it goes in and out of the prom check routine. 26 is BNE. Branch if not equal. 20 is BRANCH ALWAYS. So you took the equivelant of an "IF THEN " in the code and changed it to "goto". That is the program doesnt need the characteriser to be right it just jumps off to the next part of the program regardless. In your case address 16BD. It doesnt work with later mpu4s because the ROM test is more complex and sometimes involves trickery like bank switching etc and on BWB you can forget it!!!!

yes i see it all so

That last photo, you can see the plug with two black wires darting off underneath? Pretty sure that is directly connected to the speaker, and that plug looks like it's been dripped on!

Nice looking walls there Nick, better than any crappie family portrait! 😂😂