The LS368 at 5A was fine as was the LS107 at 5B. Problem: Dead board, no clock to the CPU.įirst thing I checked was the clock to the CPU, none, next checked the crystal and it was pulsing. Solution: Cleaned legs on custom chip 07XX at 4D on the CPU board Boom! was fine, but the rest was short chirping sounds Solution: Cleaned dirty legs of the custom 08XX chip at 2E on the CPU board Problem: Split screen, left hand side of screen was displayed twice, with a garbled vertical line of red jumbled letters down the center (the high score display). Solution: Cleaned legs on Custom 07xx chip at 1N on the Video board Problem: Sprites would kind of fade in an out, like they where only being partially drawn Solution: bad 74LS20 at location 3A on the video pcb Problem: Game plays but enemies and the player’s ship is missing. Solution: Bad 74LS368 at 3N on the video board I grabbed a LS368 and piggybacked it on 3N and the display cleaned right up. I knew there was a problem with timing, but not sure why I turned my attention to the chip next to the star field chip. Then I looked at the star field generator chips making sure it was seated well and the legs were all clean. Next I looked at the LS161s on the video board seeing that now it was losing the picture altogether now on occasion. So I replace all 8 wrams, (2148 equivalents). When I first fired up the board I would have sworn it was a bad 2147 video ram. Sprites would streak horizontally and the game would lose video sync, sometimes a row of white or light blue zeros would appear at the top and bottom of the screen. Problem: Game plays, but star field was erratic. Solution: Bad 74LS151 at 4K had stuck outputs on the CPU board Solution: Replace the CPU at 4M with a Z-80A, it had a standard Z-80 instead!!! I started to grab the freeze spray to determine if that was the problem when I noticed the CPU was a standard Z-80 and not a Z-80A. I was pretty sure there was a heat problem so I touched the top of the chips on the CPU board with my finger and found the main CPU at 4M was getting really hot. Happened more often as the board was on longer. Solution: Bad custom chip at 2J on the CPU board Problem: When the enemies entry the playfield, they are all bunched together. Solution: Bad resistor pack at RM2 on the CPU board Solution: Bad Socket on the 07xx custom on the CPU board at 4D, dirty custom chip legs I replaced the socket on the 07XX and the board would then go thru it’s diags and boot into the attract mode. After this I had the self-test starting, but it would constantly reset itself in the middle, or just hang. Solution: Replaced the eight 2147 rams with two 2149 (2148 equivalent) rams.įirst step was to clean all the customs. Problem: Players ship and the Galaga character have every other horizontal line either missing or mixed up. That socket was then inserted into the original socket. ![]() It was repaired by soldering on a new leg, then inserting it into a new socket. ![]() Solution: Pin 12 on the Custom 04xx IC at 4M on the video board was broken and making intermittent contact with the chip. Problem: Streaks of graphics trails coming off to the left of many of the characters. Solution: Bad ROM at 3N on the CPU board. ![]() Solution: Broken pin 11 on the ROM socket at 3J. Problem: Board would hang at the ROM OK during boot. ![]() Solution: Bad electrolytic caps, C20, C21, C22 on the CPU board. Problem: Sound fades in and out at random times. If you are technical and want to try here are a few common sound problem fixes to try: Please refer to installing a Galaga PCB post to install a new one. This would be a very technical fix, probably better to just go on Ebay or Online and simply buy a new working original Galaga PCB. (The Speaker is only an 8 ohm and can be replaced very cheaply) If you still have no sound with a new speaker installed, then you have a problem within your PCB transmitting the sound out from the game.
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