Sirius
Member
A brief history... the machine was only supposed to need a power supply. When I plugged it in there was only 2 of 3 led's lit (no -5) on the power supply. After some point the -5 came back on and the the machine did it's growl and the screen was scrambled. After a few adjustments to the monitor and several restarts the screen was working properly. I finally got it to show either a ram or rom error, not sure which, it was late. I was able to get past that to "game over". I coined up the machine and played 3 games, after that it was all down hill! The screen went corrupt...kinda looked like "Klingon". Now only 3 led's light on the rom board, don't blink and stay lit. I cant say that I saw the 4th led ever light. Anyway, now there "was" no video and no growl...sigh!!! I got life back in the monitor after swapping the 2 7474's, but still no growl.
Come to find out there was a bad connection on the -5 fuse holder. I've since cleaned it and re flowed the solder connections on the power supply. Tested the power in numerous spots (connectors and ram). Only suspect voltage was the 6.3vac. It's reading at about 4.5 & 5.5. I've replaced all the ram with new 4116's and re-flowed all the connectors on both the cpu/video and rom board. I've also re-seated every socket chip on the board, and replaced the 40 pin ribbon cable, but still no growl.
With the 7474's in their original sockets the mpu reset (pin 37) did not work. When I swapped the 7474's pin 37 behaves normally. With the logic probe on reset pin 37, I read a hi/lo pulse that goes low (1 sec) when the reset button is pushed. Still the reset does nothing, led's don't blink.
Can anyone decipher these values?
Pin 2 of 7L = hi/lo/pulse
Pin 5 of 7J = hi/lo pulse
Pin 9 of 7J = hi
Pin 4 of 6R = hi
Pin 8 of 7P = lo/pulse
Pin 12 of 7P = lo/pulse
...so any help would be greatly appreciated.
Come to find out there was a bad connection on the -5 fuse holder. I've since cleaned it and re flowed the solder connections on the power supply. Tested the power in numerous spots (connectors and ram). Only suspect voltage was the 6.3vac. It's reading at about 4.5 & 5.5. I've replaced all the ram with new 4116's and re-flowed all the connectors on both the cpu/video and rom board. I've also re-seated every socket chip on the board, and replaced the 40 pin ribbon cable, but still no growl.
With the 7474's in their original sockets the mpu reset (pin 37) did not work. When I swapped the 7474's pin 37 behaves normally. With the logic probe on reset pin 37, I read a hi/lo pulse that goes low (1 sec) when the reset button is pushed. Still the reset does nothing, led's don't blink.
Can anyone decipher these values?
Pin 2 of 7L = hi/lo/pulse
Pin 5 of 7J = hi/lo pulse
Pin 9 of 7J = hi
Pin 4 of 6R = hi
Pin 8 of 7P = lo/pulse
Pin 12 of 7P = lo/pulse
...so any help would be greatly appreciated.
