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Title: Ghosts 'n Goblins Bootleg repair log Post by: Zabanitu on February 26, 2012, 10:24:08 PM this board came with no program, charatcter and background eproms, only sprites eproms where present
i burnt a new set form "gngbl" and fired the board. i had a lot of background problems, like floating pins generating sparkling pixels and ghost pictures. i replaced a 28 pin socket in the bkg eproms, replaced also the 2x 50 pins flat cables that connect the 2 boards. now i had a nice picture but the red in the characters where randomly missing and coming back. this was traced to a faulty LS174 @ 4F on cpu board (intermittent output) after a little burn in the sprites developed jailbars and sometimes the game just locked up with a full white screen, i had to power cycle the board to have it working again. found a faulty 2114 @11H in video board (found by piggybacking), replacing the ram just fixed sprites corruption and the random white screen crash (probably it loaded the Address Buss too much ?) now i had a nice looking video but the background (like the little hill you find in the 1st screen) was drawn only in the first left column of the screen instead of the right side, when the whole screen was scrolled, the correct background was drawn completely reversed. after tracing with 'oscope and video probe i found a LS74 @ 14A in the video board whose output was stuck low, this prevented the correct display of the background. Fortunately capcom schematics are divided into sections and this was the SCROLL H POSITION replacement of a faulty YM3014 also fixed a missing voice in the audio generation part. Phew ! Zab Title: Re: Ghosts 'n Goblins Bootleg repair log Post by: channelmaniac on February 27, 2012, 01:19:28 AM Nice! That board set is a bitch to work on.
Title: Re: Ghosts 'n Goblins Bootleg repair log Post by: Zabanitu on June 27, 2012, 02:43:42 AM just an update:
after some hours of burn-in the board had locked up again and won't startup like 90% of the times. when it would start the screen showed "VRAM NO GOOD 20xx", other time it would just display garbage and the cpu would stop executing code. i don't have any 6809 pod so i had to work trial & error! I followed the schematics and RAM at address 2000-27FF is the 2016 character ram on the cpu board (location 7H). after tryng to replace the ram chip, the ls245 carryng data to it, i found that the LS00 @ 7F wich is responsible to decode tha R/W signal from cpu to outside world the baord was fixed. Now it boots 100% of the times and had a burn-in of several hours without a hitch. probably the previous white screen problem was generated by the flaky LS00 |