By: TAD Corporation Released: 1988 Display: Horizontal (upright only) Input: Trackball Read how I converted an Amiga Mouse to act like a Trackball Read how to build a Trackball to Joystick circuit for arcade machines (for playing games like Cabal, Rampart, Centipede, and Arkanoid) Pinout: JAMMA CPU: MC68000, YM3931 Players: 2 (simultaneous / co-operative) Identifying Marks: 4 PCB's, 2 main boards are piggybacked, and each contains a very small daughter-board marked "4MEG ROM BOARD". DAMN! I wish this one worked. Well, you takes-yer-chances at an auction. It nearly works, You hear sound, you can insert coins and play the game, but you only see the background artwork and text, no sprites. Seems like a small fix, but darned if I can track down what's going wrong. Tried all the simple stuff, check for power, re-seat chips, and checking for cold solder-joints or anything else I could think of. No luck. Funny thing is, I can completely remove the top PCB and the game operates just the same. I even had someone else (over the internet) try removing the top PCB on theirs to see if it operated the same. Sure enough, no sprites. Well, maby I'll figure it out one day. ANYONE HAVE SCHEMATICS???? WOOHOO!! After I think this has been my 4th attempt, dragging the board out of the pile, and sitting down with the ol' oscilloscope to try to track down the problem, I've succeded! I decided to attack the problem by tracing the sprite data from the ROM's output pins to the JAMMA video pins and see where the data disappeard. It didn't take long to notice that there was NO sprite data coming from the ROM's. Hmmmmmmm... he sais... Is there chip-select signals? Is there Output enable signals? Is there Address signals? Yup. But no data. Is there power to the ROM's and the address select chip? yup. So why's there no data? One of the chips must be fried and pulling all the data outputs high. That, or something on the main motherboard is doing that. How to determine if the main PCB is ok... Well, both those ROM boards look mighty similar. Lets see what happens if I swap'em! Now I see a game with no backgrounds at all, and a lot of sprites running around that have garbage for their picture! Very good sign! Something is wrong with the sprite ROM's PCB (which is, fortunately, the small PCB). I traced all ROM pins back to the header that connects to the main PCB and checked for continuity, comparing to the good ROM board from the main (backgrounds) PCB. Sure enough, one signal was not making it all the way there. A small soldering job, and the game works great!!! WOOHOO!! Resurrected Cabal! Photo of the PCB.