What causes spot killer to come on with an Asteroids board failure?

wolfeel

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Besides missing X&Y signal what causes spot killer with an Asteroids board failure?

Just doing some reading of the schematics and was wondering, besides missing X or Y output signals what causes the spot killer to come on when there is a board failure?
 
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I found out recently that you could have a good working board and a good working harness and a good working power supply/AR1 and a good working monitor and still get spot killer - if you forget to hook up that little 6-pin connector on the deflection board between the two deflection transistor connectors. :D

Of course, no signal from the board (if the game is set to free play and the start buttons don't blink but stay lit constantly - means the board isn't running) will do it, but some other various problems on the monitor could cause it like - blown fuses, bad frame-mounted transistors, etc...
 
I will get more specific but bear with me because i am still learning. Using an Asteroids board as the example what upstream from the DACs will cause the spot killer to trigger? I am guessing the vector generators will cause the spot killer to trigger; correct? Is that where it stops in reference to parts on the board?
 
If one ROM is bad, spot killer can come on. If the processor is bad, spot killer can come on. If the crystal is bad, spot killer can come on. Get the picture?

I think what you're really trying to ask is - my board is powering up properly, my start buttons are blinking, I can start a game and hear it playing, and I know my monitor works properly because I tested it in another game, so why is the spot killer on? Correct?
 
If one ROM is bad, spot killer can come on. If the processor is bad, spot killer can come on. If the crystal is bad, spot killer can come on. Get the picture?

I think what you're really trying to ask is - my board is powering up properly, my start buttons are blinking, I can start a game and hear it playing, and I know my monitor works properly because I tested it in another game, so why is the spot killer on? Correct?


No, if that was what I was going to ask I would have just asked that specifically. I was just looking at the schematics the other day (specifically the X Y output part) and thinking to myself what else would cause the light to come on. It makes sense that only parts related to the video generation would cause the spot killer to come on when it is caused by a PCB failure. The question should have been what else on the board contributes to the video generation upstream from the DACs?
 
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