Missile Command missing +5v

TheDrewster

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Just picked up a Missile Command tonight, it looks to be a bit different in terms of your traditional Atari power supply setup. I dont have any schematics or manuals to work off of at the moment, but I am only getting +2 something on the +5v line. Is it safe to assume its just a shot ARII board?
 
Scratch that. ARII is tested working, but the game only boots to two solid player lights. No activity. Monitor is completly shot so I am just looking for blind playing at the moment.
 
The manuals and schematics are available here at:

http://www.arcade-museum.com/game_detail.php?game_id=8715

Dokert has posted a good tutorial (video) on how to troubleshoot and test the ARII somewhere in the forums, but I was unable to find it.

Look on pages 42 and 43 of the manual - you are interested in Q1, which is the 5 volt linear regulator.

If you haven't cleaned the board edge connectors and tried to clean up the pins on the ARII, I'd suggest starting there, or metering the pins between the ARII connector and the game board. A high resistance connection could easily drop the voltage and create heat in its place, and knock MC off line.
 
Voltages are good, I swapped ARIIs with my Warlords and Missile Command's ARII works in my Warlords no problem. I have heard the edge connectors on the harnesses are crap on these, and it looks like someone put a coat of solder on the fingers of the PCB and the harness connector looks to be in bad shape because of that. I suppose I should address that next.
 
Scratch that. ARII is tested working, but the game only boots to two solid player lights. No activity. Monitor is completly shot so I am just looking for blind playing at the moment.

Often a sign that the board isn't booting. Does it go into test mode? Have you cleaned and reseated your ROMs? Do you have a logic probe?
 
Often a sign that the board isn't booting. Does it go into test mode? Have you cleaned and reseated your ROMs? Do you have a logic probe?

Does not go into test mode. I have not reseated any ROMs or anything yet, but I do have a logic probe. I think I need to address the edge connector issues first before I go poking around on the PCB.
 
Does not go into test mode. I have not reseated any ROMs or anything yet, but I do have a logic probe. I think I need to address the edge connector issues first before I go poking around on the PCB.

I see. Well, I'd check the +5 test loops on the PCB and see what you're getting there… Should be around 5.1VDC, adjust if you aren't getting that.

If you have good +5 on the PCB and it's not booting, it's time to break out the logic probe. Check the clock pin on the CPU to see if it's running, then check the RST pin to see if it's watchdogging. And clean/reseat those ROMs, you'd be surprised how many weird issues this can fix. Had an Asteroids PCB that would work for a few minutes, then start resetting and going crazy, triggering the lockout coils, beeping, etc. Cleaned & reseated the ROMs, and it's been solid since.
 
Also find and check the +12 and -5 test points. MC has DRAMs (and possibly PROMs) that require tri-voltage (+5/-5/+12).
 
It should be noted that the ARII board for MC is a -03 version. This is not the cause of your 5v problem but you may want to check it once you get that issue resolved.

http://www.elektronforge.com/AudioRegs.htm

It was my understanding a -02 board would work unless you've got the earlier version board with like 12 roms on it. No?
 
Probably the -02 will work with the 6 ROM version. I have not done a measurement to know one way or another. It is possible that the 11 ROM version will work with the -02 if the specific board draw is low enough. Just thought I would mention it to you.
 
Alright, so I have found that I am measuring 5.12 at the harness, then 4.93 at the PCB test point. Safe to assume a bad edge connector?
 
You have something playing (with the voltage drop), and the edge connector is the most likely culprit to start with. It could also be a weak solder joint, but start with the easy stuff - burnish the connector on both sides, as well as the board.
 
I've got a new molex for the harness and a PCB edge repair kit coming from Bob. We shall see how this works.
 
If you had a way to measure the current on the 5 volt leg, we could calculate the resistance.

For now, you can power the game off, find the 5 volt wire, and check the connector by ohming between the orgin and the board end of the connector. If you find resistance, move the ohmmeter probe to the wire at the connector, and at the board. If you still have the resistance, it's the connector / board interface. If not, it's something with the wire (pinched, stretched, damaged).

It's highly likely that it's the connector (>97%). It is not very likely to be a wire problem, but stuff happens.
 
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