Missile Command CT/ ARII help

Mitsurugi-w

Well-known member

Donor 2011
Joined
Jul 8, 2009
Messages
2,387
Reaction score
43
Location
New Bern, North Carolina
Hey guys.

I put my MC cocktail out on location in one of my stores today. I had left it on for several days to make sure everything was good before removing it from the house. I put it in the restaurant and it worked for an hour and then started to reset. I turned it off a few times to reset the harnesses on the pcb and ARII and kept getting solid or rolling screens. The third time I turned it back on, R30 on the ARII burned up.

Now obviously I need to rebuild the ARII. I was unable to test voltages before it burnt up. What exactly does R30 do and what is the value. Is it likely that a voltage problem on the ARII was causing the resetting or is R30 burning up unrelated?
 
The usual cause for R30 burning up is weak or bad Edge connectors on the main game board. R30 is a 10 ohm 1/4w, some people bump them to a 10 ohm 1w.

Yes, the A/R II failing is what was causing your restting issue.
 
Thanks. The edge connector seemed pretty tight so I don't know if that's bad. I'll test it further. I'll put a rebuild on the ARII and see how it goes from there.
 
Thanks. The edge connector seemed pretty tight so I don't know if that's bad. I'll test it further. I'll put a rebuild on the ARII and see how it goes from there.

Save yourself the headache.....about the only thing that will burn up R30 on the A/R II board is a shot edge connector. Replace the resistor on the A/R II board.....cut that edge connector off...and crimp a new one on. On a side note.....if your harness has a Molex brand edge connector....you don't need to cut it off (if it's an Amp brand, sorry, it's time to cut). Buy some new Molex pins....pop the old ones out....cut and crimp new ones...done. You won't even have to do all the pins....just the power/grounds/sense.

Edward
 
Save yourself the headache.....about the only thing that will burn up R30 on the A/R II board is a shot edge connector. Replace the resistor on the A/R II board.....cut that edge connector off...and crimp a new one on. On a side note.....if your harness has a Molex brand edge connector....you don't need to cut it off (if it's an Amp brand, sorry, it's time to cut). Buy some new Molex pins....pop the old ones out....cut and crimp new ones...done. You won't even have to do all the pins....just the power/grounds/sense.

Edward

Also, I highly recommend the sense mod...

ar2linkdone2.JPG


Jumper those pins as shown, then R30 and R29 will never be an issue again... neither will a dirty or loose edge connection. You don't even have to replace the resistor if you do this. You'll have to adjust the voltage again, measuring on the game PCB, but it'll save you a LOT of headaches.

EDIT: By "never be an issue" I mean "won't burn up your A/RII board". Clean as suggested, replace if needed, rebuild if warranted... then do the sense mod... and do it on ever A/RII you come across in the future.

Just my 2 cents.
 
I recommend a 100 Ohm 1/4W resistor. The schematics say 10 Ohms but what was actually used on production cards was 100 Ohms. Probably because 10 Ohms was too low and taking too much leakage current and heating up.

Or just do the sense mod and be done with it. :)
 
Also, I highly recommend the sense mod...

Jumper those pins as shown, then R30 and R29 will never be an issue again... neither will a dirty or loose edge connection. You don't even have to replace the resistor if you do this. You'll have to adjust the voltage again, measuring on the game PCB, but it'll save you a LOT of headaches.

EDIT: By "never be an issue" I mean "won't burn up your A/RII board". Clean as suggested, replace if needed, rebuild if warranted... then do the sense mod... and do it on ever A/RII you come across in the future.

Just my 2 cents.

Just so I understand, the idea here is to simply disable the sense circuitry, so that the power supply won't eat itself in certain odd situations (bad sense lines from the game PCB being the one in question), right?

Is it worth doing a rebuild on the A/R II if it's not giving me any trouble? I don't want to fix it if it's not broken, but doing the sense mod looks to be a good precaution (I just lost a ram due to a loose PCB connector) and if I'm going to have it out of the system anyway, now's the time for me to do the upgrade.
 
Just so I understand, the idea here is to simply disable the sense circuitry, so that the power supply won't eat itself in certain odd situations (bad sense lines from the game PCB being the one in question), right?

Is it worth doing a rebuild on the A/R II if it's not giving me any trouble? I don't want to fix it if it's not broken, but doing the sense mod looks to be a good precaution (I just lost a ram due to a loose PCB connector) and if I'm going to have it out of the system anyway, now's the time for me to do the upgrade.

If you do the sense mod......yes, the sense circuit will never give you a problem again.....but.....and this is a big but......people seem to forget this......The sense mod IS NOT a fix for a shot edge connector. A bad edge connector is what kills the sense circuit. If you do the sense mod, but do not replace the edge connector (or at minimum, replace the voltage and ground pins in the connector).....you WILL eventually burn up the edge connector fingers on the mothertboard. With the sense mod installed.....you will no longer burn up 2 three cent resistors on the A/R II board......now you'll burn up the fingers on the motherboard. It will take a lot longer...but it'll happen (unless you address the actual problem....shot edge connector pins).

Edward
 
)....you WILL eventually burn up the edge connector fingers on the mothertboard. With the sense mod installed.....you will no longer burn up 2 three cent resistors on the A/R II board......now you'll burn up the fingers on the motherboard. It will take a lot longer...but it'll happen (unless you address the actual problem....shot edge connector pins).

Edward

The big difference here is that with the sense mod done, in order to have the game operate normally, you have to manually adjust the +5V sense to compensate for the bad edge connector. So, you'll have no excuse when you burn up the edge connector. :)

I do recommend a rebuild kit even if the AR is running fine. The business parts on those are nearly 30 years old and are now prone to failures. The big monster is the 2N3055 +5V tranny. If it goes you will very likely get the full +12V on your +5V line. You know that Pole Position board you just spent $150 for repairs? Kiss that goodbye.

Also, NEVER operate an AR with damaged R29/R30 sense resistors or without the sense mod done. Especially if you're transplanting the AR from another game.
 
Last edited:
The big difference here is that with the sense mod done, in order to have the game operate normally, you have to manually adjust the +5V sense to compensate for the bad edge connector. So, you'll have no excuse when you burn up the edge connector. :)

I do recommend a rebuild kit even if the AR is running fine. The business parts on those are nearly 30 years old and are now prone to failures. The big monster is the 2N3055 +5V tranny. If it goes you will very likely get the full +12V on your +5V line. You know that Pole Position board you just spent $150 for repairs? Kiss that goodbye.

Also, NEVER operate an AR with damaged R29/R30 sense resistors or without the sense mod done. Especially if you're transplanting the AR from another game.

I'm not against the sense mod....though, I find it unnecessary if the actual problem is fixed :)....My biggest problem with the "sense mod" is people arn't informed about what the real problem is. They think the sense mod is a cure all. The pins in the edge connectors need to be replaced.

And I do agree with you about the 3055. I can't tell you how many working Atari games I see in the shop.....when I check the 5VDC line.....8-12VDC pumping down it. I always wonder how much longer they'd last.....and how long they've been running this way?

Edward
 
Totally agree! I encourage the sense mod since it makes the user cognizant of how much more voltage (or power) they're having to push through the pins.

The AR gets no respect tho - it's relatively inexpensive next to the main board, but is just as important.
 
The big difference here is that with the sense mod done, in order to have the game operate normally, you have to manually adjust the +5V sense to compensate for the bad edge connector. So, you'll have no excuse when you burn up the edge connector. :)

I do recommend a rebuild kit even if the AR is running fine. The business parts on those are nearly 30 years old and are now prone to failures. The big monster is the 2N3055 +5V tranny. If it goes you will very likely get the full +12V on your +5V line. You know that Pole Position board you just spent $150 for repairs? Kiss that goodbye.

Also, NEVER operate an AR with damaged R29/R30 sense resistors or without the sense mod done. Especially if you're transplanting the AR from another game.

Thanks guys. I'm one who doesn't like to make mods without understanding the reasoning behind them. I don't know if I'll do the sense mod. I'll have to check the connector - it comes off too easily, but I've actually got too much wire there, which may be pulling it around. I suppose the right thing is to swap the relevant pins/connector, but I'll have to look at what that's going to cost me.
 
Thanks guys. I'm one who doesn't like to make mods without understanding the reasoning behind them. I don't know if I'll do the sense mod. I'll have to check the connector - it comes off too easily, but I've actually got too much wire there, which may be pulling it around. I suppose the right thing is to swap the relevant pins/connector, but I'll have to look at what that's going to cost me.

All the mod does is cut the connector out of the picture. Instead of reading the voltage THROUGH the edge connector (where it has to go through the connector pads that can be dirty), it reads the voltage directly at the power supply.

I have a Pole Position that refused to read the correct voltage... cleaned the edges, connector, and pins... would still bump the voltage up to 7V+, bad juju. I did the mod, and I'm getting the +5 I needed, without fry'ng parts on my board. Again, always clean the pads, connectors, and pins... but if you're still having issues, I do recommend the sense mod. While the worst that can happen on your A/RII is a couple of burnt resistors, over voltage can still damage your game boards.

I guess it's all personal choice, but as for me, I'll never run an A/R board without doing the mod. I have 4 stacks of PP boards, all fried in the same place... all from different cabinets... all fried for the same reason. It's just a little extra peace of mind for me to do the mod, I guess.
 
Bob Roberts sells the split pins for the edge connector. I replaced all of them in my Tempest, in an effort to track down an intermittant connection (which ended up being the interboard connector instead).

Joey
 
So should I replace the entire harness or just the pins in the harness? The harness in my cabinet is one where each wire is soldered to the individual pin rather than crimped. If I need just the pins, which ones exactly do I need from Bob Roberts? I did notice some slight blackening on some of the end pins on the edge connector.

This is my first ARII experience so forgive my noobish questions. The sense mod makes it so that the voltage has to be tested on the ARII rather than on the PCB? Is this correct? Is the purpose of the sense circuit to compensate for incorrect voltages?
 
So should I replace the entire harness or just the pins in the harness? The harness in my cabinet is one where each wire is soldered to the individual pin rather than crimped. If I need just the pins, which ones exactly do I need from Bob Roberts? I did notice some slight blackening on some of the end pins on the edge connector.

This is my first ARII experience so forgive my noobish questions. The sense mod makes it so that the voltage has to be tested on the ARII rather than on the PCB? Is this correct? Is the purpose of the sense circuit to compensate for incorrect voltages?

The purpose of the original sense circuit is to detect what voltage the main board is actually seeing and adjust to make sure it's getting the 'correct' voltage. It does this by having +5 come back from the main board via the sense line.

What I'm understanding is that old pins often make the sense line unreliable, which makes the sense circuit over-voltage the main board, thus possibly causing damage on the main board, and/or blowing resistors on the A/R II board.

The sense mods defeat this problem by forcing the sense circuitry to see the voltage present on the A/R II board, instead of the returned sense voltage from the main board.

This means that you no longer get the A/R II board automatically adjusting for proper voltage on the main board, but instead you get the A/R II board no longer accidentally blowing out parts on the main board.

After the sense mod, you'll want to adjust the A/R II voltage based on readings on the main board, NOT on the A/R II board. You'll also want to make sure that the connectors to the main board are good, otherwise you're still likely to have other problems.
 
So should I replace the entire harness or just the pins in the harness? The harness in my cabinet is one where each wire is soldered to the individual pin rather than crimped. If I need just the pins, which ones exactly do I need from Bob Roberts? I did notice some slight blackening on some of the end pins on the edge connector.

This is my first ARII experience so forgive my noobish questions. The sense mod makes it so that the voltage has to be tested on the ARII rather than on the PCB? Is this correct? Is the purpose of the sense circuit to compensate for incorrect voltages?

Sounds like someone has already replaced yours with a "solder eyelet" style connector. You can't replace pins in those...your only option is to replace the entire connector. I recommend the Molex "crimp" over the "solder eyelet" style. Bob Roberts sells both.

Edward
 
Sounds like someone has already replaced yours with a "solder eyelet" style connector. You can't replace pins in those...your only option is to replace the entire connector. I recommend the Molex "crimp" over the "solder eyelet" style. Bob Roberts sells both.

Edward

Do you recommend those because it's possible to replace single pins? Or is there another reason?
 
Do you recommend those because it's possible to replace single pins? Or is there another reason?

I think they're better on many levels.....Yes, you can replace only the bad pins if need be.....solder eyelet type tend to break at the solder/connector housing base.....the crimp type pins are better.....and you're only talking about a $1 or so price difference. Now, you have to know how to crimp, and have a decent crimping tool.

Edward
 
Ok. I'm set to rebuild this ARII tonight and reinstall it tomorrow. I'm going to do the sense mod also. My question is: Once I rebuild it how do I go about setting the voltage? With PCB connected while using the sense mod right? Do I just use any 5v test point on the pcb?

Also, lets just say I don't do the sense mod, how do I set the voltage on the ARII (in case I work on someone else's machine)?
 
Back
Top Bottom