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Ice Storm
04-13-2004Stargate - Upright
Trying to fix the sound output now. Since the new power supply doesn't put out -12V I tried using the -5V and it seemed to work, so now I have a fully working Stargate again.
04-05-2004Stargate - Upright
After my power supply went crazy, it caused 27 volts to go through the +12V line! Of Course my RAM didn't like that, so it went on fire and self destructed! First thing I did was to replace it with the newer kind of power supply, which are more reliable anyway. I found a hack to convert the ram to more friendly 4164 which just runs on GND/+5, so I replaced all the RAM with 4164s ($24). Turned on and got a flashing 1-2-7. Replaced that RAM and it was still flashing 1-2-7. Replaced the socket and it works! Woohoo! However no sound yet.
02-02-2003Klax - Upright
Monitor seemed to work, but there seemed to be no life from the game itself. First thing to check was power supply. Input volatages were normal, output voltages were all 0. Replaced power supply. Game came up with no other issues. An easy fix.
02-02-2003Bubble Bobble - Upright
Monitor was dead. Can coin up machine and game appeared to be functional. Tried cap kit on monitor board. Monitor still dead. No glow in neck of monitor (either tube issue or board issue). Tried monitor board with another tube and it worked, so the problem was bad tube. Replaced tube with my spare one and replaced monitor board. Monitor came up nicely. Several of the buttons and joystick directions weren't working, so I need to test/replace the microswitches.
09-13-2002Space Invaders - Taito cocktail
There were multiple problems with this machine, there were 2 sounds that were not working. The first was the invader explosion sounds, this was fixed by replacing the LM3900 amplifier chips at locations 31 and 32. The saucer explosion sound was fixed by replacing the LM3900's at locations 30 and 33. For the LM3900's I replaced them with NTE992 which is a valid replacement. When the invaders moved down, they left 2 pixels behind them on the previous row. On my board I have 8 x 74LS151, 2 x 74LS174, and 2 x 74LS175's that replace the MB14121 custom chip. It was one of these chips that was bad, in this case it was the 74LS175 at location 13. Pin 1 on this chip was apparently not connected to anything which seemed strange, since all the other related chips were connected together, so I connected pin 1 of this chip to pin one of the other 74LS174/175's. I couldn't find any schematics showing my board, so the problems were kind of tough to find and resolve, but I did it.

© 2002 Hugh McLenaghan
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