No announcement yet.

Rastan Saga Repair Log

  • Filter
  • Time
  • Show
Clear All
new posts

  • Rastan Saga Repair Log

    Offered to take a look at a Rastan Saga board that Mickaz had picked up on ebay as faulty, was sold as having graphics issues.

    The game would run but the intro screens were a mess and the sprites were all mangled, the sound was also weak and rather raspy.

    Thats the main character!

    Turns out its a bootleg which can be both good and bad, good that there are likely to be few customs on it, bad that info on them can be scarce, MAME often doesnt have bootleg versions of games as the incentive to get yet another version of the game going is low once the original version is perfectly emulated.

    In the case of this board it was a bad thing, I started of probing around and quickly found my way to PROM A18 on the top board, interupting the outputs on this chip made the messy stripes in the main sprites slightly less messy, still wrong but a more neater kind of wrong.

    Pulling this chip out confirmed I was on the right track, the lack of data for those stripes makes them drawn as complete striped blocks.

    Its clear that the data for the sprites are contained within a pair of PROMs on this board. Pulling out the one next to it at A22 made the game display sprites as just blocks of red, ie the strips of good gfx data are missing and replaced with red stripes too.

    So I went to dump A18 and my eprom reader detected out of spec pins, so I went looking in the MAME romset for the data - trouble was the MAME set is not the bootleg and the rom layout is very different to this board. The main game has fewer ROMs but larger capacity ones, and at different board locations.

    So I dumped all 28 roms from the board and fired up a hex editor to see what was what. Took a while to find a match but eventually I found that $00000 to $08000 of the non bootleg version Rastan chip ic14_07.bin 1st was A20.bin from this board.

    I figured that all the gfx data would be held in a bank of roms on the original board so I tracked down a decent photo of the original board and found that IC14, IC15, IC27, IC28, IC39, IC40, IC66 and IC67 are PROMs. PROMs and or mask ROMs are usually used for data that isnt going to change, ie sound and graphics data. The program code is often held on EPROMs which are more expensive but allow any bugs to be fixed at a later date. Working through these 8 ROMs I worked out that....

    From Rastan Set

    ic14_07.bin 0x00000-0x08000 is A20.bin
    ic14-07.bin 0x08000-0x10000 is A26.bin
    ic14-07.bin 0x10000-0x18000 is A19.bin
    ic14-07.bin 0x18000-0x20000 is empty

    ic15_05.bin 0x00000-0x08000 is A22.bin
    ic15-05.bin 0x08000-0x10000 is A28.bin
    ic15-05.bin 0x10000-0x18000 is A21.bin
    ic15-05.bin 0x18000-0x20000 is A27.bin

    ic27_08.bin 0x00000-0x08000 is A16.bin
    ic27_08.bin 0x08000-0x10000 is A23.bin
    ic27_08.bin 0x10000-0x18000 is A15.bin
    ic27_08.bin 0x18000-0x20000 is empty

    ic28-06.bin 0x08000-0x10000 is A25.bin
    ic15-05.bin 0x10000-0x18000 is unknown
    ic15-05.bin 0x18000-0x20000 is unknown

    ic66_04.bin 0x00000-0x08000 is unknown
    ic66_04.bin 0x08000-0x10000 is A4.bin
    ic66_04.bin 0x10000-0x18000 is empty
    ic66_04.bin 0x18000-0x20000 is empty

    ic66_04.bin 0x00000-0x08000 is A5.bin with mods at start
    ic66_04.bin 0x18000-0x20000 is A3.bin

    From Rastan Saga set

    rs07-37.bin is A12
    rs09_43.bin is A14 very minor mods
    rs21_42.bin is A11 very minor mods
    ic76_20.bin is A1

    This suggested that A18 was likely to be in ic28-06.bin either at 0x0000-0x8000 or after 0x10000 somewhere, so I wrote the 1st option to a new eprom, dropped it in and got all the sprites back.

    So - ic28-06.bin 0x00000-0x08000 is A18

    The chip at A7 tested as being flaky when I was dumping the ROMs, it showed up as having faulty data lines so I was pretty sure this was the causing some of the problems. It would be fairly easy to find where the A7 data is in the mame set if I had the contents, in which case I wouldnt need to go looking anyway - all I had was a load of rubbish data from a duff PROM to go on, and no clues as to where it might be anyway.

    I had already put a plea out for anyone with the same board who could dump some ROMS, SectionZ replied and confirmed that A7 contained the same data as IC39_03.BIN, so I burnt a new rom and that fixed the mashed title screen and intro.

    Next issue was the sound - very weak, volume pot didnt do much to it, and the sound was raspy. I had noticed initially there was a cap that had been wrenched to one side, dragging its guts out.

    The amp chip has been fitted with the labelled side downwards, and the legs looked fragile, as did the solder side of the board so I didnt want to bend it up, or desolder iut. So I couldnt find out what that cap is for, but it connects to the amp chip, anyway replacing the cap fixed the sound fault. Ran ESR tests on all other electrolytics on the board and they are all fine.

    The only remaining oddities are sparkles in the text when the game is booted from cold, they fade away pretty quickly and I am now fairly convinced they are caused by a bank of PAL chips on the lower board. If I crash the game there is about a 3 second wait before the watchdog notices and resets the CPU, during this time there are no sparkles, if they were due to faulty RAM they would continue as long as the bad area was being addressed. The likelyhood of fixing this issue is slim, PALs tend to be security locked, even if I had a working board here it is highly unlikely I could get the data off the good ones to replace these. They get damn hot (normal for PALs) and hitting them with freezer spray makes the sparkles increase. After the game has been running for 2-3 mins they are pretty low level and not that noticeable.

    The other oddity is that this game is perfect at 4.7-4.8V measured on the board by the JAMMA connector, voltage drop to the furthest reaches is only 0.1V, but increasing the voltage to 5V makes the foreground elements flash on and off randomly, ie all sprites, icons and text. Returning it to 4.7V makes all these issues go away, I cant find anything obviously wrong to be honest - I suppose it is possible that this is just one of those very fussy boards, odd that it likes the volts lower than normal though!

    Oh and I also soldered the volume pot in properly, from new it was leaning at about a 45 degree angle, one pin was barely touching the soldered pad - bloody bootlegs, assembled by drunk chimpanzees

    Thanks again for your help SectionZ!
    Last edited by Womble; 26th July 2009, 07:03 PM.
    Sic transit gloria Atari!

  • #2
    Err.. How could you solder a chip in upside down?


    • #3
      I didn't say it had been soldered in upside down...

      Originally posted by Womble View Post
      The amp chip has been fitted with the labelled side downwards... is a SIP type amp chip and it is fitted to the board in such a way that the labelled face is down against the PCB, and the heatsink side is facing upwards. You can see it in the last photo. The legs don't look like they would survive much bending so I would have to desolder it to see what type of amp it was, to find the datasheet to find out what that cap was for - not much point seeing as the cap replacement fixed the sound.
      Sic transit gloria Atari!


      • #4
        as usual very thorough mate well done.


        • #5
          nice work! what do you use for esr testing ?

          HookedOnDefender,TimePilot,CrushRoller,1942,Pacman [original ghost in the machine!] VIDS: DefenceCmnd, Defender(2),Stargate(2),Joust,Joust2,MoonPatrol,Ph oenix,PolePositionII, Pacman, MsPacman, DKJr, MarioBros, LunarRescue,SegaTurbo,FujiSpeedRace PINS: Gottlieb Gladiators WANTED: Robotron, Sinistar, Maketrax, Timepilot & Defender Pinball! SOLD:Qix,Qbert TRADED:Gorf


          • #6
            don't know about Womble but i use this one (love it)
            If it isn't broke then don't fix it!


            • #7
              Yup - thats the exact same one I use, I bought it from Dickies when they were flogging off all their useful stuff cheaply to make room for junk in their new stores. Only cost me $25
              Sic transit gloria Atari!


              Users Viewing Topic: 0 members and 1 (guests)