Tempest PCB: corrupt vectors, otherwise game plays.
Just started doing a little troubleshooting and figured I'd take a video to show just what is going on. The video shows the output on a scope which when the monitor is connected shows the same thing. The scope leads are connected to the XY test points. BTW, X=~18Vpp and Y=~14Vpp.
http://www.youtube.com/watch?v=fPkHgzc1U3A
As you can hear in the video(sound starts at the 12s mark), the game appears to be playing fine there is just garbage on the screen.
So far I've rebuilt the A/R II(just because), re-soldered the interconnect pins, cleaned all socketed chip pins, checked the ROMs, put in a new 6502(shot gun attempt), replaced one POKEY(had no sound before replacing), and replaced D/E12, D/E13, and C12.
The reasoning behind replacing the TL082CPs was I read that the IO of the DAC(pin 18) should be zero and when it's not, it's a sign that the related TL082CP is shot. Replacing both didn't seem to change the XY output or the IO signal.
The reasoning being replacing the 1495 was more out of curiosity... I've read that these go bad semi-often and just took a shot in the dark. Needless to say nothing changed.
I've looked at the inputs to the DACs on the scope and they seem to be fluttering away. I looked at all of the X DAC inputs and most of the Y DAC inputs and none were stuck high or low.
Next on the list is research. I just want to read more and look at the schematics to try and come up with a game plan. I posted this "just in case" someone else has run into this or has any ideas.
-Jeff
Just started doing a little troubleshooting and figured I'd take a video to show just what is going on. The video shows the output on a scope which when the monitor is connected shows the same thing. The scope leads are connected to the XY test points. BTW, X=~18Vpp and Y=~14Vpp.
http://www.youtube.com/watch?v=fPkHgzc1U3A
As you can hear in the video(sound starts at the 12s mark), the game appears to be playing fine there is just garbage on the screen.
So far I've rebuilt the A/R II(just because), re-soldered the interconnect pins, cleaned all socketed chip pins, checked the ROMs, put in a new 6502(shot gun attempt), replaced one POKEY(had no sound before replacing), and replaced D/E12, D/E13, and C12.
The reasoning behind replacing the TL082CPs was I read that the IO of the DAC(pin 18) should be zero and when it's not, it's a sign that the related TL082CP is shot. Replacing both didn't seem to change the XY output or the IO signal.
The reasoning being replacing the 1495 was more out of curiosity... I've read that these go bad semi-often and just took a shot in the dark. Needless to say nothing changed.
I've looked at the inputs to the DACs on the scope and they seem to be fluttering away. I looked at all of the X DAC inputs and most of the Y DAC inputs and none were stuck high or low.
Next on the list is research. I just want to read more and look at the schematics to try and come up with a game plan. I posted this "just in case" someone else has run into this or has any ideas.
-Jeff


