Missile Command - ARII and PCB Questions

Michael Roma

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I just picked up a non-working MC and am trying to get it back up and running.

I checked voltages on the ARII without the PCB connected first to make sure everything was fine. All voltages were on except the +5V which was high and unadjustable at 5.7V across the positive leg of big capacitors but +4.66V at J17 pin 5 and pin 6 and 2/B on the edge connector.

I figured that the +4.66V was fine and wouldn't hurt the board, plus I wanted to see how far the +5V line dipped under load, so I connected the PCB. I powered it up and of course the game didn't play and +5V LED lit but when I went to test the voltage at the +5V test point I saw smoke coming from the Q2/R5 area of the ARII. I immediately turned the game off and unplugged the game PCB. I powered it back on and test the voltage and they read the same as before.

So I pulled the ARII and replaced Q3 (2N3055) as well as Q2, Q8 and Q9 since I had it out. I put it back in and powered it up again w/o load and was able to dial the +5V down but the -5V is now hovering at -14.9V.

Any ideas what could be causing the -5V to be that high? Will plugging in the game PCB damage it with the -5V that high?

- Mike
 
If you replaced the -5 volt regulator with one from Bob Roberts....it'll regulate down. For some reason, his run "high" without a load. I'd try powering it up with a load "really quick".

Edward
 
The AR-II board wasn't designed to run unloaded. The +5 tries to auto-regulate itself based on a sense line from the MC PCB (basically, a returned +5). If that isn't present (that is, if you run it without the PCB), AND if you haven't done the requisite mods, you'll usually find the AR-II burning itself out.

Here's the description of the sense mod that I used: http://www.stickycarpet.com/pinx/ar2mods.html

If you do the sense mod, realize that what you are doing is making it impossible for the system to automatically adjust the +5, so you'll need to check it on the PCB, and possibly adjust by hand.

If you don't want to do the sense mod, make sure the PCB connector is good (all pins should make good contact, connector should go on firmly, no corrosion on the pins), the fingers on the PCB are clean (I like DeOxit, myself), and that the connector doesn't get knocked loose while you are testing.

Now, as to the -5: that's just what it does unloaded. Plug in the PCB and it should be fine.
 
I plugged the board in and powered the game on. I dialed the +5V in and checked the 12V and -5V on the PCB. All good.

I checked the monitor and had nothing but a blue tint. Oh well I thought. I turned everything off and was about to call it a night when I decided to see what it does in self-test. I put it in self test and got the sounds that the manual said I would. I reset the power, coined the game up, pressed P1 and heard the game playing blind. I go to the back of the game to check the monitor and notice that the video cable is not plugged into the chassis. Power the game off, plug in the video cable to the chassis and power it back on. Now I have video but the horizontal sync is off.

I need to see if I can adjust it out with the horizontal hold pot but figured I made enough progress tonight and I'd leave that until tomorrow.

Thanks for the help thus far gents.

- Mike
 
I plugged the board in and powered the game on. I dialed the +5V in and checked the 12V and -5V on the PCB. All good.

I checked the monitor and had nothing but a blue tint. Oh well I thought. I turned everything off and was about to call it a night when I decided to see what it does in self-test. I put it in self test and got the sounds that the manual said I would. I reset the power, coined the game up, pressed P1 and heard the game playing blind. I go to the back of the game to check the monitor and notice that the video cable is not plugged into the chassis. Power the game off, plug in the video cable to the chassis and power it back on. Now I have video but the horizontal sync is off.

I need to see if I can adjust it out with the horizontal hold pot but figured I made enough progress tonight and I'd leave that until tomorrow.

Thanks for the help thus far gents.

- Mike

Dude, you got this far and didn't spend another 30 seconds to tweek the horizontal hold/frequency pot? :)

That would have kept me awake all night!

Edward
 
I did end up going down after the post and messed with the horizontal hold to no avail. I thought I would be able to resist but figured the same thing about losing sleep thinking about it... :)

I woke up early this AM and capped the monitor and check B+ but the sync issue is still there. I searched the forums and saw something about wrong value resistors installed on some G07s at the factory so that is next to check.

Here is a video of my issues...

http://home.comcast.net/~mtpacifico/_arcades/missilecommand/missilecommand.htm

- Mike
 
Yep, Your horizontal frequency is way off. What's the video signal connector look like? Is it wired correctly?

Edward
 
Well I had another G07 chassis on hand that I swapped in the cabinet and had the same results. So, it looks like it might actually be a PCB issue.

What on the PCB could be the culprit? Is there anyway to test the H/sync on the game board w/o an o-scope?

- Mike
 
If you have a logic probe check the output of A6, Pin 8 which is the HSYNC signal.
 
I checked using the below logic probe and pin 8 on A6 (as well as the H Sync test point on the board) gave me a solid red light.

I have had this for years but never used it. I connected the black clip to the ground test point and the red clip to the +5V test point on the board and probed A6, pin 8 and the H/Sync test point. Is that the proper way?

The logic probes I've seen online have both a red and green LED for low/high states while mine appears to only have a red LED.

So what does my solid, steady red LED tell me?

- Mike

logicprobe.jpg
 
I checked using the below logic probe and pin 8 on A6 (as well as the H Sync test point on the board) gave me a solid red light.

I have had this for years but never used it. I connected the black clip to the ground test point and the red clip to the +5V test point on the board and probed A6, pin 8 and the H/Sync test point. Is that the proper way?

The logic probes I've seen online have both a red and green LED for low/high states while mine appears to only have a red LED.

So what does my solid, steady red LED tell me?

- Mike

logicprobe.jpg

I can't say for sure, but my guess that one led would light for high and go off for low.
Try probing some other spots on the board and see if you can see the led changing. Try things like data lines or clock lines to see if you can get an indication of what he probe would look like in various situations.
 
I plan on picking up a logic probe on the way home from work tomorrow...

Also, I was searching the internet and stumbled across Bob Robert's Big Blue page and saw this...


Here are 5 Big Blue Symptoms that are eroneously blamed on the monitor.
  • 1 Intermittent lightning streaks in pic/hum bars/weaving.
  • 2 Blank raster... steady or intermittent.
  • 3 Jumpy pic sometimes described as jiggles.
  • 4 Failure of H hold to lock in.
  • 5 Intermittent vertical roll or failure to lock in.
Has anyone experienced an issue like this that was remedied by replacing the Big Blue? I have a spare power brick from I believe a Pole Position. Are the power bricks in Atari games interchangable? Could I swap that power brick in my MC to see if the problem persists?

- Mike
 
I plan on picking up a logic probe on the way home from work tomorrow...

Also, I was searching the internet and stumbled across Bob Robert's Big Blue page and saw this...


Here are 5 Big Blue Symptoms that are eroneously blamed on the monitor.
  • 1 Intermittent lightning streaks in pic/hum bars/weaving.
  • 2 Blank raster... steady or intermittent.
  • 3 Jumpy pic sometimes described as jiggles.
  • 4 Failure of H hold to lock in.
  • 5 Intermittent vertical roll or failure to lock in.
Has anyone experienced an issue like this that was remedied by replacing the Big Blue? I have a spare power brick from I believe a Pole Position. Are the power bricks in Atari games interchangable? Could I swap that power brick in my MC to see if the problem persists?

- Mike

I don't know if PP has the same brick as MC upright or not. Atari did change the brick regularly - the MC Upright does NOT, for instance, have the same brick as used in the cockpit, cabaret and cocktail MCs. They tended to change the look of the brick as well as the connectors, so you should be able to easily see if they are the same.
 
I know but I was hoping that I could swap the Big Blue in and catch a break and the game will work...

I swapped the unknown condition Big Blue and have the same thing...

I can't test the logic on A6 as suggested because nowhere around here sells a friggin' logic probe. I don't need to tell you about the blank stares I got when I asked the people at Radio Shack if they had one (and then what it was for)... but that is another story. I'll just have to order one online and wait for it to arrive.

In the meantime... I think I might have a tube of LS7474s lying around. Could I piggyback one on the questionable chip and power the game up... or am I just swinging in the dark at this point?

- Mike
 
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