Gorf

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

  • Lady Bug

    Board ID 8016 : Falcon version ? Static graphics on screen, dead – pin 24 low on Z80, /WAIT signal. Trace signal on board to 74LS74 at E7. Signal incorrect for inputs. Replace with new one, board fixed.

  • Atari Tetris

    In normal mode, just had a blank screen. Enable test mode and you instead get an error message showing that the ROM test had failed (even though the rom itself checks out OK with correct content) This is because the custom Atari SLAPSTIC chip is not functioning correctly. It is used to page banks of…

  • Gallag

    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….

  • Make Trax

    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…

  • Rainbow Island

    On power up – black screen, no sign of life at all. I removed the 68000 CPU and fitted a socket, so I could use the Fluke on it. This revealed that the main program ram ($10C000-$10FFFF) was totally dead. Replacing the two ram chips IC25 and IC26 solved this problem. Board now started up,…

  • Neo Geo

    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….