Crime City – Taito

Another PCB on the bench from my friend Sasha: Taito Crime City. It’s a run and gun arcade game, that was released by Taito Corporation, in 1989; it runs on Taito B-System hardware, and it is a spin-off from Chase HQ, which had been released in the previous year.

The PCB was in very good conditions, clean and with no apparently damage, once the game has been powered up, we were been greeted with this …

An unstable and rolling image all over the screen, it’a a clear sign of a sync related issue, the game seemed to respond in the right way, it can be coined up, the audio seems working, also the players controls seems to work, i say “seems” because trying to play the game in this way produces some kind of “seasickness” … LOL.

… and what’s happening inside the game wasn’t so clear! But it’s time to investigate.

I looked at the sync signal on JAMMA harness and as we suspect it was completely stucked at ground level, an healty sync signal should tick instead. I traced back the sync signal through the PCB up to a pullup resistor connected to VCC (+5v) and then up to an output pin of an IC, an HEX buffer with open collector outputs, a 74LS07.

You can see the sync signal path marked in yellow colour, the signal is fed into the IC into pin 1 and then it comes out from pin 2, here is the logic diagram of the IC:

So before making any assuption about the possible causes of the issue we should point the scope over the input and the output of the IC to see what’s going on … the input is in BLUE (pin 1) and the output is in YELLOW (pin 2)

As you can se the input is correctly ticking at the right frequency (15.7Khz) while the output is stucked at ground level. In the output signal path the only discrete components were a pullup resistor, a ferrite bead and a capacitor and even if one of these components were damaged the sync signal shouldn’t be stucked at ground level, so the IC should be damaged and short circuited its output pin internally to GND (ground). Confident the issue was related to the IC malfunctioning i promptly remove it.

Testing it out of circuit confirm our suspects, the interested logic unit was failing:

and then socketed and replaced …

Powering up the board ends up with a perfect and stable image displayed on the screen! The sync signal now is ticking and healty as it should!

Case closed!

6 thoughts on “Crime City – Taito”

  1. Hi, sorry i have no schematics for Taito Crime City.

    Here’s a list of Taito games running on almost same hardware “Taito B System”. Finding one of these schematics may be useful.

    Ashura Blaster
    Crime City
    Hit The Ice
    Master Of Weapon / Yukiwo
    Puzzle Bobble / Bubble Buster
    Quiz Sekai wa Show by shobai
    Rambo III
    Rastan Saga II / Nastar / Nastar Warrior
    Real Puncher
    Ryujin
    Sel Feena
    Silent Dragon
    Sonic Blast Man
    Space Invaders DX
    Tetris
    Violence Fight

  2. Hey, can you help me with my Masters Of weapon? Mine had a weird purple layer on top and lots of color bleeding, the game is perfectly run underneath, i have changed the TC0180VCU and Tc0260DAR with know working ones but that won’t changed.. what it could be?? thanks

  3. Thanks, i have maneged to fix it by myself. There was a 2018 ram underneath the Z80 wich made me think it was related to the sound area but in the end that was not the case, it was directly pointing at my problem (with a bad NPN to follow). Sorry if i ask you here, are you able to fix Titan STV motheboards? Matteo will let me know if you answer me, he is your bodyguard hehe. Thanks

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