Missile Command Cocktail repair help needed

Droler

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Just acquired a MC CT; it has a randomly occurring vertical roll - you can adjust it out using the control on the monitor but it comes back during game play.

So far I have capped the Sanyo 14"monitor with a kit from Bob Roberts and it still does the same thing; there is also randomly occurring static like graphics corruption - and the cities don't look right after being destroyed.

I replaced an obviously damaged ARII board with a known working one. The rolling slowed down and it held longer, but it still occurred.

I also found one ROM socket with a faulty pin.

The self test finds nothing wrong - RAM and ROM check out.

I want to order parts from Bob Roberts (like a Big Blue for starters) but I need advice on what parts may need replacing. Voltages all checked out but I noticed a tiny bit of fluctuation on the 12V which I blamed on the Big Blue.

Here's what the city graphics look like:

105_0012.jpg


Here's an example of the "static":

105_0009.jpg


Also, someone did a wire hack here:

105_0014.jpg


And finally, this part was damaged on the old ARII board but putting in a non-damaged one didn't see to make a difference. What is this part?

105_0015.jpg
 
The burned component is R30, which is part of the 5V sense circuit. YOu also have a hacked harness there with that fat wire soldered to the board (ground or 5V return). Seems likely they are related (think AR-II sense mod).

Also, whats going on with that IC right next to the DIP switch, is there schmeg on those pins?

The rolling is due to poor V sync... I had that happen on mine at one point, but I think I had the sync hooked up to the wrong polarity input on the monitor. I _think_ MC is positive sync and I had it connected to neg sync?

Of course big blue can be the cause of many sins...
You should rebuild the edge connector on that game tho and elimintate that
nasty hack. Check the connectors on the AR-II end also just to be sure.

hope this helps a bit... I'm sure one of the MC experts (bit_slicer? Mark S?) will chime in!

cheers
/Tim
 
Droler, re your graphics problem - look at this page:

http://www.arcades.plus.com/repair.htm

just over half way down you'll see a fault that isn't exactly the same as your but which does affect the colouring of the cities. The repair log for that mentions the chips to check and while I'm not saying it's them it might give you a starting point if you have a logic probe.
 
That's an interesting problem! At first I thought bad DRAM(s), but then it appears to be only in the 3rd color region with the cities. I don't have the schematic in front of me but I'd say there's a problem with how the address circuitry is pulling playfield data in that region. Whatever it is, I can fix it. :D

 
Bit_Slicer - can you PM me a price and turnaround time?

I can do this myself but I have not had time lately.

This is a Christmas gift for a best friend who's like a brother to me (Missile Command makes me break out in hives - I'm a Galaga/Gyruss type of guy) so I want to make sure it's working 100% by December.

Here's more information from today.

I noticed the static like graphics are from overscan. The horizontal width needs adjustment. Going to get a tool for that and fix it. You'll notice above in the pics that it only occurs when the ground is overscanning outside the sides, mostly at the bottom. So I am removing that from the list until I get the adjustment right.

The pots on the monitor board are shot - so vertical and horizontal adjustments are hard to nail. Could that be the cause of the rolling?

Lastly, I think the city graphics are the only part that are caused by the PCB. Notice how after they are destroyed they have vertical "spikes" coming out of them.

I am going to order a big blue cap, horizontal coil adjustment tool, and the replacement resistor and an ARII refurb kit.

Should I order anything else (if you were going to do this, what would YOU buy)?

This is directed to everyone - and thanks you guys for the replies.
 
Bump for one final request for additional help. I ordered a big blue cap from Bob along with an ARII kit to rebuild the bad one and a HZ adjust tool.

If anyone has any other advice I'll take it...

Thanks to Bit_Slicer for the price quote via PM...
 
OK, I tried posting this over in monitor help but no one is biting:

Been working some on a Sanyo 14" monitor in a missile command CT.

Some of the new things I learned may help diagnose this monitor's problems. I'm hoping it's something simple.

The two symptoms are

1) Random rolling vertically. It can be adjusted out but the range of position the vertical POT can be in is infinitely small. And once you get it to sit still, a few minutes later, it will slowly start rolling again in either direction. The longer it stays on, the worse the problem gets.

2) Horizontal width coil doesn't affect the width. I saw something from a Fromm article about changing a capacitor that might help with that - but the coil on this chassis does not appear to adjust at all.

I should also mention the problem with the width is that it's too wide. Just barely - it overscans the edges.

Time's running out since this is *supposed* to be a Christmas gift, but not unless I can get a stable picture. Everything else is working fine.
 
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