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

  • 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…

  • Neo Geo

    Byadmin

    6 Slot – Memory test on power up giving error  Address    Write Read  00008000 5555 55FF Checking with Mame, the memory chips in question were only small, so looking at the board revealed two DIL 5814’s. Chip select signals to these were toggling as expected, so I needed to identify which ram chip was which….

  • Hantarex MTC9000/A

    Byadmin

    No picture, Hole blown through LOPT. Had problems tracking down replacement – little tip given to me by Hantarex engineer – you can use the LOPT from an MTC9000 as long as you cut pin 2 off. (If you leave it connected, you will get a direct short to GND)

  • 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,…

  • 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…

  • Carnival

    ByMichael Coates

    Carnival on a Gremlin / Sega Vic Dual PCB. Just had blue bars on screen, although probing the Z80 showed it was trying to run code. Using a logic probe I discovered that the /WRITE signal of the ram chips was always high. This signal comes from a 74LS10 at U77. Checked this chip and…