1 Player Start button LED not illuminating on Missile Command

Quomonster

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Clearly this is a "nice to have" working as opposed to game play critical. I did some testing and found that the LED in the switch is good and that it is not receiving the flash signal from the game board. I managed to find the 2 Player start signal coming off the board using the logic probe, but was unable to find the 1 Player start signal coming off the board. This brings up a couple of questions.

First, I see that Start LED 1 is referenced as "P" on the edge connector and should feed a W/R wire. Start LED 2 is referenced as "H" and should feed a W/B wire. I am having difficulty determining how the referenced numbers and letters correspond to the edge connector / socket plug connector positions. Is there a standard for how these are laid out? Do I start counting down one side and then in reverse down the other side? I am assuming that H would be 8 spaces away from P on the same side of the edge connector. It is difficult to see the colors of some of the wires in the harness, so I was looking for a "map" of some sort. On the schematic the wires are shown in a "random" order that is more suitable to the layout of the drawing. Any suggestions here?

The other thing is I can't find anything in the schematic that indicates which chips on the board are related to the Start LED outputs. I do see in the memory map that a D1 bit somewhere in the high 48xx region is responsible for 1 Player Start LED Output. So there is the possibility of bad RAM causing the problem, but this seems unlikely since the game is otherwise almost completely working. (it also has the missing Earth problem which I am pursuing here, btw):


Can anyone tell me how to determine which chip / pin should be feeding the 1 Player Start Led Output, so I can attempt to test the chip and possibly other related components on the board?

As always, any suggestions are greatly appreciated - please and thank you!

JC
 
MC_LED.jpg


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Welcome aboard to the best resource for all things "arcade game restoration/preservation"!

See here for missile command specific info. This will help you ID what is what on the edge connector. Also search for "clean edge connectors" for some useful general maintenance info.

Also note Atari skips letters G, I, O, and Q on the edge connector.

Also, BTW... please learn how to use the search function on the forum BEFORE posting a question... there is a treasure trove of info here. Some members get a bit grouchy if you don't use the search function first... but most of those same fellas are happy to help if you've exhausted all efforts to locate the info you need!

Good luck
Dylan
 
Wow, thank you both very much!

@journeymandt that is exactly what I needed - I was having trouble with the right search terms, I tried atari wiring harness, missile command pinoutS, etc. - but now I see that I could have found it with more persistence! same goes for...

@VectorCollector - also exactly what I needed. I stared at that schematic for some time, and am feeling pretty dumb at the moment. I hate to admit that I looked very closely at the output section and I just couldn't see it. I also did not realize those are the pin numbers in the boxes at the edge of the diagram. It's starting to make sense, thank you!

To put things in perspective, this is the first arcade machine that I've worked on - thank you folks for your patience - the assist is very much appreciated!

JC
 
did you try swapping buttons? the lamp in P1 start could just be bad

also make particular note which wire pair is for the lamps and which is for the switch
 
Thanks again to @VectorCollector and others who commented!

After your assist I found R81 reading several meg ohm and ordered a replacement. I will get that soldered in asap, fairly certain that will restore the LED functionality. Will let you all know how it turns out.
 
indeed, R81 was the problem and the LED is working once again - thanks for the assist!
 
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