What SMOKED my R29 on Atari AR-II board? (photo included)

Steverd

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What SMOKED my R29 on Atari AR-II board? (photo included)

I'm still working on the Battlezone, and while testing all of the caps on the board, I noticed R29 was burnt so I replaced that and two caps with high ESR reading. After putting back into the game and starting up, I smelled smoke.
YEP, the R29 burned up in about 5 seconds... OK what on the AR-II 02 board would cause this? Oh yeah, also R30 is fine and tested OK.

R29.jpg

Thank you as always!
 
This is a very common problem w/ the AR-II boards. It's a 10 ohm resistor. Make sure you have good contact on the edge connector and good voltage feeding back on the sense wire!!! Long story short, the sense line on the AR-II "returns" the voltage from the main PCB back to the AR-II board. If there is a difference between the +5v on the board and voltage being returned, the AR-II cranks things up to make up the difference. Many times the edge connector on an Atari PCB doesn't make a good connection and returns low voltage on the sense line in which the AR-II ramps things up. R29 is between the +5v and the sense line. It's only a 10 ohm 1/4 watt resistor and takes the brunt of the extra power. Up to 2.5 watts through a 1/4 watt resistor will let out the magic smoke. If that is the case, either replace R29 with a new resistor or there is a "sense mod" you can do to prevent that problem. Some people suggest against the sense mod because it defeats the purpose of it. If you have good connectors and good solder joints, you shouldn't have any problems. These games are going on 30 years old and new connectors and reflowed solder isn't such a bad idea. You can actually bump up to a 1/2 watt flame resistant resistor. If you want to do the sense mod and bypass that "feature" all together, here is a link on what to do. http://www.stickycarpet.com/pinx/ar2mods.html
 
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Check your fuse holders, they are prolly loose..

Most of the time r29 is burnt when you have a loose connector. I'd bet that's your issue.. As all of the connectors to the pcb had a lifespan of maybe 5 years
 
Check your fuse holders, they are prolly loose..

Most of the time r29 is burnt when you have a loose connector. I'd bet that's your issue.. As all of the connectors to the pcb had a lifespan of maybe 5 years

The fuse holders on the power supply??
Argh, just had that out as I replace the Big Blue capacitor..

Thanks,
 
yeah and I started installing R29 about 1/2" above the a/rII (until I figured it out) so I wouldnt put anymore burn marks on the board. :)
 
I agree, if the game edge connector is burnt or dodgy the sense circuit fries R29

I happened on my star wars AR2 the other day

Fix the edge connector PCB and Connector, fix the Ar2.
 
Pull the PCB today, the small PCB looked good, but the main PCB looks like this
on edge connector #2 is I think is the +5V REG. I will try to clean with an eraser or fiberglass pen or alcohol or something.

pins.jpg
 
The discoloration is overheating, not merely dirt. The properties of the metal are permanently changed so cleaning will not really fix it. May I suggest a jumper wire for that particular pin

I am doing that for the Star wars PCB until I do a more permanent solution
 
The discoloration is overheating, not merely dirt. The properties of the metal are permanently changed so cleaning will not really fix it. May I suggest a jumper wire for that particular pin

I am doing that for the Star wars PCB until I do a more permanent solution

Thanks for the info.
How about flowing a think layer of solder out from the hole to the edge?
Might not stick though. I fixed an edge connector on my Centipede about 5 years ago with a thin piece of copper soldered in place. Still works to this day.
I wonder what I did with the rest of it? I might have an edge connector replacement I got from Bob Roberts years ago, but where did I put it??
 
Thanks for the info.
How about flowing a think layer of solder out from the hole to the edge?
Might not stick though. I fixed an edge connector on my Centipede about 5 years ago with a thin piece of copper soldered in place. Still works to this day.
I wonder what I did with the rest of it? I might have an edge connector replacement I got from Bob Roberts years ago, but where did I put it??

Yes, a soldered copper piece will work, but may permanently stretch the female side of the edge connector. If you ever fit a different game board, the stretched connector will pass on the damage to the new game pcb
 
Yes, a soldered copper piece will work, but may permanently stretch the female side of the edge connector. If you ever fit a different game board, the stretched connector will pass on the damage to the new game pcb

Thanks, I actually found my Edge Repair kit that I got from Bob Roberts at least five years ago. I think I should just do this and make it permanent (and right)!

edge-1.jpg
 
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