Gorf

ByMichael Coates

Capacitor burnt. (game board), particularly at C37 the capacitor was showing signs of extreme heat. Replaced them all with 22uF 25V axial electrolytics.

No Speech / Some SFX missing. (game board) Output from speech chip SC01 was OK, as was output from IO Custom (X3). checked transistors in output stage and 2N4401 was faulty. (Q2)

Glitches at sides of screen

Screen glitch. (game board) Screens using twinkle circuit (stars etc.) had visible glitches down each side. These did not interfere with game play but looked bad. Tracked down to faulty 74LS161 on game board. (U16 on this one, but also check U15)

Similar Posts

  • Gallag

    ByMichael Coates

    Ran through self test OK, came up with chequer board screen and then reset most of the time. Occasionally would start game, but with credit noise continually playing and credits rapidly counting upwards. This is caused by CPU 4 (E5) not running properly. checked the eprom and ram (C5,D5 and E5) and ram was faulty….

  • Galaxian

    ByMichael Coates

    No display – When move board, display flickers – go around board pushing each chip in turn, when press on 2E picture appears. Pin 16 rusted, only just in place. replace chip – picture back to normal. No star display. Board had been hacked to play an alternate game, pin 15 on chip 2B had…

  • Frogger (Sega)

    ByMichael Coates

    Missing Chip. This was a converted moon cresta board. The IC at 1.2S (shoehorned in sideways between rows 1 and 2 by the sprite ram) was missing. This was not featured on any schematics I had, so I traced the connections to see what it could be. It basically takes the output from the sprite…

  • Missile Command

    Byadmin

    The board originally failed to get into the game, instead resetting just after drawing the ‘MISSILE COMMAND’ logo. Test mode faired a little better, managing to report RAM OK, MAP OK and ROM OK before resetting. Ram and Rom checked out OK using the Fluke. Measuring various CPU signals revealed that the interrupt seemed very…

  • Sega System 16

    Byadmin

    Altered Beast – Colours missing, no reds, other colours looked like diminished palette (like windows in 16 colours) – used test mode to perform ram test, and one ram chip identified as faulty (I10). Replaced this and red was back, but still reduced pallette. Looking at colour circuit, and it uses resistor arrays driven by I11…

  • Namco Time Crisis 2 Gun

    Byadmin

    One of the guns on a Time Crisis 2 was no longer registering shots on the screen. Following checks on wiring, cleaning lens, etc. it appeared that the optical sensor (opto) was dead. This is a small PCB in the gun, 2421961100, pictured above. I couldn’t find any schematics or information about the parts used,…