omegaman
Active member
Ok I have another set arrive today that has been sent over for repair by IFKZ
The main board looks very clean, the sound board looks like its been in a fire
I pulled all the chips that were in sockets, 10 of the Ram were dead
The CPU checked out good as did the program Rom.
The video Rom failed (bad checksum).
I installed new Ram and Rom and powered it up using a spare sound board. It passes self test now but the picture on my scope showed a flat line across the screen. One of the 4016's in the vector output stage had been changed...I swapped it out and got a full screen........of garbage. You can play a game and there is movement but it is very corrupt. Swapped the Dac's ...no change so it looks like something wrong pre DAC but not far enough back to trip the watchdog.
I will have a prod around the board later and check a few chips, then time to clean up the old sound PCB.
The main board looks very clean, the sound board looks like its been in a fire
I pulled all the chips that were in sockets, 10 of the Ram were dead
The CPU checked out good as did the program Rom.
The video Rom failed (bad checksum).
I installed new Ram and Rom and powered it up using a spare sound board. It passes self test now but the picture on my scope showed a flat line across the screen. One of the 4016's in the vector output stage had been changed...I swapped it out and got a full screen........of garbage. You can play a game and there is movement but it is very corrupt. Swapped the Dac's ...no change so it looks like something wrong pre DAC but not far enough back to trip the watchdog.
I will have a prod around the board later and check a few chips, then time to clean up the old sound PCB.
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