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

  • Dark Seal

    ByMichael Coates

    Glitched graphics. Screen changes as board is flexed. Moved around board pressing chips until pressing the custom surface mount chip at B6 changed the effect. Noticed that the corner most pins had come up from the board. After an unsuccessful effort to resolder them, I used some enameled 38 swg wire to solder from the…

  • Mr Do!

    Byadmin

    Blank screen, Blanking line to output colour proms always enabled. Trace back to 74161 in timing circuit – output stuck, input clock all look OK – replace chip and picture appears. Blue video only – The video lines are controlled by three transistors near the edge connector, checking these revealed that 2 were not giving…

  • 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,…

  • The Invaders – Zaccaria

    Byadmin

    Totally dead, no screen display (blank white screen).  For this I used the Fluke Z80-S2650 adapter to check out the ram and rom, and located two errors. The rom mapping was incorrect, with a large range of locations returning random values. Examining the board (since I have no schematics), all of the chip select lines meet up…

  • Make Trax

    Byadmin

    Boot up with garbage, quickly clears screen and then nothing. Used Fluke with Z80 pod – read rom OK, and write ram OK, but timeout reading any Ram location. Check fluke status and ‘wait’ always set. Check pin 24 of Z80– stuck low, trace back through 7H,7C,6C1 to 6B1 pin 2 – always low, although…