| PACMAN FIXES |
| 9/12/02 - Ms Pacman, colored garbage on screen, moving around a bit and then stopping in place. Lifted pin 9 on 74LS74 at 8C blocking /IRQ signal from CPU. CPU was unable to respond to interrupts generated by other hardware devices. Replaced pin into socket and board operated normally. 9/20/02 - Several switches apprear to be engaged at the same time - intermittent problem. RM8 resistor pack was not pulling up inputs all of the time causing switches to appear closed to the logic board. Operational sypmtoms included no control of Pac character during game play and all test sounds play simultaneously during test mode. Replaced bad RM8 and inputs registered and cleared normally. 10/29/02 - Ms. Pacman, board runs with no maze and blocks instead of characters. No sound. Character ROMs 5E and 5F had been plugged in backwards and ound PROMs 1M and 3M were missing. Installed fresh character ROMs and sound PROMs and board ran normally. 11/29/02 - Ms. Pacman, board had been used for parts for quite some time. All RAM and ROMs were missing along with parts of the Power Supply and various TTL devices, 35 items in all. Spent 3 hours with a soldering iron in hand and board ran with characters moving in a jerky manner with wrong colors and in the wrong places on the maze. ABC diagnostic kit indicated problems with motion drives 2S, 3S (74161s) and motion object color RAMs 3F, 3H (7489s). Solder bridge found in the vicinity of 2S and displaced circuit trace next to 3F (shorting pins 1-5 together). After removing solder bridge and repositioning the offending trace, the board ran correctly. This one was a personal victory for me. I managed to revive a long dead board that nobody thought would ever run again. 12/1/02 - I went one step further with the Ms. Pac board of 10/29/02. It had been previously modified to run on +5V and +12V directly. Whoever had done this removed several parts of the power supply and wired in jumpers. I reinstalled the heatsink, D6, D7, D8, IR1, Q3, and removed the jumper wires. The power supply puts out a nice +4.9V The board has been running in my Pacman cabinet for several hours and seems to be quite happy. |
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