CPS1 Street Fighter II: World Warrior - PPU Transplant

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    • CPS1 Street Fighter II: World Warrior - PPU Transplant

      Remember the Street Fighter II: World Warrior PCB I mentioned about last week?






      Turns out to be my other WW had issues more than just wrong dip switch settings. :(

      Anyway, I ended up having no working WW PCB :) and I decided to fix the first WW which I shelved as spare parts.

      I've narrowed the problem to the C-board by swapping aorund A B C boards and testing. Also @Apocalypse helped providing evidence that the culprit for such a massive graphics glitch is most likely is the PPU2 itself.

      Still, for a last resort, I've checked ALL the legs of the PPU2 for bad solder points and tested ALL the continutiy from the legs to the C-board connector pins. All checked OK. Moreover, I've tested ALL the signals (from the connector pin tips) with my oscilloscope and didn't find any "funny" looking signals either. Yes there were some pins stuck to either GND or 5V but don't have any info if they are valid signals or not. Just didn't noticed anything floating between 0-5V.

      Anyway, after ruling everything out, its time to replace the suspect PPU chip. Which was a CPS-B-05 model;




      Now, where to find a replacement for that?

      Option A: Use the CPS-B-21 from my spare part CPS2 A board

      As @Apocalypse mentioned in one of his writings the 21 has some differences that won't fit to my current C board pin-by-pin. Need another PAL hanging around and also need a "modified" WW program rom set which is compatible with 21 which does not exists in official capcom releases.

      Option B: Find another C board PPU from my collection that I should be comfortable to sacrifice the game and must have a compatible rom set release.

      After going through my "bootleg" and "hack/conversion" pile, I found this:




      This is a C-Board from my Chinese bootleg Cadillacs & Dinasours. The hack was based on a 100% bootleg B-board with a PIC microcontroller and although the game graphics were OK without any obvious glitches, the music loop was extremely nerve breaking... Never put this in a cabinet and never had a plan to either play it or sell it. Afterall I've purchased it very cheap and was planning to use it as a spare part and now the time has come ;)

      It is a 88622-C-5 type C-board and main problem with this C-board was the bastard bootlegger back-in-the-day has scratched the PPU model number to protect his secret :(
    • So to identify the type of the C-board PPU I first tried this PCB on my Magic Sword and Final Fight. Neither booted... So I ruled out this PPU was not a CPS-B-04 and CPS-B-13.

      I've checked the mame source code and identified the official usage of PPUs on 88622-C-5 C-boards, there were still bunch of alternatives. Man this board was a "very" common board back in the day.

      Anyway, I made a magnified investigation and noticed this...




      The bootlegger scrathed the code good, yes, but left a tiny evidence... Notice the straight white line ?(look where the red arrow points) It seems to be the last remainder of a "4"

      That was my evidence that this PPU must be either CPS-B-04 (Which was not because I tested on my FF) OR a CPS-B-14

      I've checked the mame source code and found one official revision of World Warrior which uses a CPS-B-14 PPU!!!




      I've collected enough evidence (and courage) to begin the transplant :)
    • Now the journey begins...

      First I removed the stickers on the C-board and PPU itself. Then heated my rework station :)



      After a while with carefully heating the legs (not the chip) by passing the nozzle regularly over the four sides of the chip and carefully inserting the tip of my twizzers underneath the chip from one of the corners, the chip is now free from the PCB...




      Now the next step is to remove the solder residue from the solder points of the PCB. To do this I heat them with my rework station's hot air blower in one hand the clearing the melted solder with my solder sucker in my other hand...



      This is a faster method than using a solder wick ;) And the result is more clean. Why are we doing this BTW? Without removing those solder residues there is no way you can align the chip legs with the solder points. No way... ;)

      After cleaning with IPA (Isoprophyl Alcohol) and que tip, the PCB is now ready for the transplant...

    • The second phase in our operation is to remove the new PPU from the donor C-board. For this I'll use the heat gun but this time I have to be careful not to burn the connectors. Although the PCB will be useless without the PPU, I may still need the connectors later for spare to fix another PCB or may be I can transplant another PPU to this C-board, who knows... Anyway, we are not savages after all :P

      To protect the connectors from burning/melting, I cover them with Kapton tape. This tape is heat resistant...




      And after the same threatment, the PPU is desoldered and no pins damaged or no solder pads lifted...

    • Now the last phase...

      To solder a chip lots of legs first thing you do is to align it. Without the solder bumps on the pads, this can be achieved by hand in a few minutes. Then with your one hand, press the chip (not to firmly) with one finger, pour some no-clean flux on the corners of the chip and put some solder on at least three corners with your iron on your other hand. This is to fix the chip. Sounds a bit complex but really after a few practice, it can be done ;)




      The rest I cannot show you on a single photo. It is called "drag soldering" and you can watch youtube videos about it. Really I learned that technique from youtube :) The tip is; use no-clean flux, lots of it ;)



      And clean your work with IPA, a touth brush and cue tips...

    • Now the million dollar question. Did it worked? :) I mean I took all the hassle for just a small evidence that may or may not be correct...

      Anyway, burned the rom set (Rev I) and fired up the board :) Fingers crossed...



      i'll be damned!!! It worked... :D :D :D

      Now its time to put the stickers back and finish the repair...





      PPU transplant and finding the right ROM set suitable for that PPU fixed the problem... Enjoy!






    • yavuzg wrote:

      To protect the connectors from burning/melting, I cover them with Kapton tape.
      oh man, I've got a bunch of that stuff for 3D printing, I never thought of using it to protect parts of the PCB from heat. I'll have to remember that!


      yavuzg wrote:

      Now its time to put the stickers back
      did you make new stickers? if not, how did you remove them without damaging them?
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