I got an M92 PCB here that uses MASKROM’s from SHARP.
These MASK’s in particular are pin compatible for either 27C020, 27C040 or 27C080 EPROM’s.
It is possible to determine which to dump these as from the markings on the chip. They all begin with the ID LH53#, where # is the identifier of the size.
“LH532” = 27C020 dump
“LH534” = 27C040 dump
“LH538” = 27C080 dump
The remaining letters/numbers of the markings are unique to the game and location on the PCB.
Sometimes it is very annoying when you have placed your arcade monitor vertically and certain games are shown upside down and even worse they have no option to flip the screen.
It happens very often with older games but sometimes even with newer games from the 90s.
In these cases you have 2 options: reverse phisically your monitor or reverse the yoke on the pcb of the monitor (not very safe).
Now I show you a new option available only when the games were also prepared for cocktail tables (that means they have already the circuit to flip the screen for the second player)
In this first “flip screen” hack I will take Zaxxon / Future Spy hardware as an example
These games have no flip screen option but they have the preparation for cocktail tables play.
The board is very big but luckily schematics are available and they are very clear to understand.
The hack is very simple: input nr.4 of 74ls367@U64 is normally LOW for first player game and HI for second player game.
We have only to force pin 4 to HI (+5V) using a wire so that the screen is always flipped as it was playing the second player even in upright mode.
Very simple and effective!
Ace’ has tested the Bay Route (317-0116) decrypted set and report it works fine.
Thanks to Ace’
Got a very clean Megazone pcb for a repair. The board was in near mint conditions but it didn’t boot and also the Sync was missing.
Looking at the schematics available online, I noticed that the quartz responsibile for the CPU clock and sync was the one placed on the bottom board.
Tested with my frequency meter and it was dead.
It is a very rare 18.432mhz OSC which to my knowledge is used only by early 80s Konami boards.
Luckily I had a Double Dribble which I used for spare parts which had the very same OSC.
After changing it, the game booted perfectly.
For you information, if you try to install the more common 20Mhz OSC, the colours are off and the scrolling is jumping often, so unfortunately it’s not a good replacement.
The board had no sound but I immediately noticed that there was no noise coming out of the speaker which is the evidence of a faulty amplifier.
The amplifier is infact the very unrielable LA4460N, so after confirming the the music could be hear on input pin 2 , I exchanging it and fixed completely the game.
Today I’ve dumped the PALs from a World Rally PCB.Board has five PLDs but I could successfully dump two of them since the other three are registered.Original devices were two TIBPAL20L8 which I reversed and tested fine onto GAL22V10.