Grbgemen
Active member
When i got my F-14, every once in awhile, i noticed it would not boot. Only happened once in awhile. Now that i have finished repairing stuck solenoids/lamps rows and cleaning the play field up, i am now stuck with a F-14 that will only boot every once in awhile.
i started with the guide on pinrepair. pulled the cpu and hooked it up to an old atx power supply. tried this first:
CPU did not boot. So my understanding that the POR section is fine. Well i ended up replacing all the components that the guide says anyway.
Next i wanted to check the voltages from the game power supply just to be sure they were in range. they all tested fine. i think i can rule out the game power supply as sometimes the cpu will not boot when on the bench.
I also have tried replacing the 6802 CPU chip at U15 and the ram chip at U25. I checked all six of the 6821 PIA chips and they all test fine.
The only thing i have not replaced is:
i tested each chip and all readings were fine. if these chips are bad or are going bad, will the game still boot sometimes?
this thing is driving me nuts. for example, i just got in from replacing the U25 Ram chip. The board booted on the bench. when i put in the game, i got nothing.
i started with the guide on pinrepair. pulled the cpu and hooked it up to an old atx power supply. tried this first:
To "go around" the POR section of the board, you can do a simple test. After attempting to boot the CPU board, ground the /RESET line on the CPU chip (pin 40 of U15) momentarily with a test clip. If the board boots up consistently without a problem (correct flashes or "0" in the LED), then the POR section is definately at fault.
CPU did not boot. So my understanding that the POR section is fine. Well i ended up replacing all the components that the guide says anyway.
Next i wanted to check the voltages from the game power supply just to be sure they were in range. they all tested fine. i think i can rule out the game power supply as sometimes the cpu will not boot when on the bench.
I also have tried replacing the 6802 CPU chip at U15 and the ram chip at U25. I checked all six of the 6821 PIA chips and they all test fine.
The only thing i have not replaced is:
Check the 74LS244 chips at U11 and U13.
If either of these two chips is bad, the game will never boot. Check both of these chips using your DMM with the game off. Set your DMM to the "diode" setting, and put the red lead on ground (pin 10). Then put the black lead on pins 1-9 and pins 11-18. You should get a reading between .4 and .6 volts. If you get a short (zero) reading, replace that chip.
i tested each chip and all readings were fine. if these chips are bad or are going bad, will the game still boot sometimes?
this thing is driving me nuts. for example, i just got in from replacing the U25 Ram chip. The board booted on the bench. when i put in the game, i got nothing.
