The conversion of Major Title to R-Type 1
Day 3: De-Solder & Replace the N0, N1, N2 & N3 Sprite Roms..
Time to fit the remaining TTL Logic & SRAM chip..
There are several modifications to the motherboard to be carried out in this final section..
Firstly, cut several tracks on the underside of the top-board - here:
(Looks rough, but that pictures are extremely zoomed in.)
Next-up you have to add the new 74LS32 Quad OR Gate to one of the spare chip 'slots' on the board..
Quite why iRem had added 'unused' spare chip sites to their board is anyones guess.. perhaps they expected to have to bodge the boards post-production?
Either way, they are a welcome coincedence for what we want to do.. the original guide recommends using the chip-site towards the outer corner of the PCB, however my board had an iRem sticker over that one..
So I located the OR-Gate in the next site along:
Next, you piggyback the SRAM & 74LS244 Bus-Tranceiver, like so... taking care to follow the instructions on bending out the correct pins & ensuring the correct chip orientation.
Then all that remains is to just connect it all up with some patch wire.. (just he says)
..and power her up! *drum-roll*
Ta-da! One humanly-affordable R-Type 1 Arcade board \o/
Massive thanks and the upmost respect to Paul Swan and Chris Hardy for the original conversion technique.. and for doing all the really hard-work!
And a massive thank you to the various members of the Jamma+ forum who helped make this project possible, particularly; ben76, Jenginner, PaulCan69, Lee-Lee & Vib.
It must be noted that the modification of Major Title to R-Type 2 is a little simpler than the mod above..
(Fewer board modifications are required & you don't need the extra SRAM chip & logic iirc.)
Overall, it took about 22 hours and cost about £20-£30 in spare parts (in addition to the Major-Title board).
That also assumes you already have the tools to hand!.. (I didn't and it ended up being about £150 all-in - still half the price of the original board though!) and most of the time was taken up by de-soldering & chip-extraction (pays not to rush!).. but it should be possible to reduce that given more experience.
Right, I'm off to destroy the Bydo empire..