ARII-02 smoked R30

gibbous

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Just got a Centipede cabaret today! Had it plugged in for a bit, left the garcade, then came back and smelled that magic smell. Looked at my ARII and saw this:

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The game was still running in attract mode, but I didn't leave it on or try to play it. Anyone ever see this before? What did you do? I'd like to repair this ARII if possible, but I've never worked on them before, just want to know what I should check before replacing the resistor and just plugging it back in.
 

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That is actually fairly common, so much so that Bob Robert's rebuild kit contains the resistor. Replacing the connectors is usually the solution.
 
yep, it's usually caused by a poor connection between the edge connector on the PCB and the molex connector to the harness. it's possible this came loose during transport and this happened if you didn't reseat the molex connector before turning the game on. it could also be a bad or bent pin on the molex connector. look at the main PCB for any burnt pads on the edge connector then check the corresponding pin.

it looks like those caps may be original on your AR-II so you might as well get the Bob Roberts kit and do the whole thing.
 
R29 and/or R30 smoked are classic symptom of the edge connectors on the main board being too dirty or damaged. Bob Roberts sells rebuild kits for the AR-II, but they only have one 10-100 Ohm resistor. For best results get two 100 Ohm 1/4W resistors and replace both R29 and R30. Then do the AR-II rebuild kit.
 
You can also up it to a 1/2w resistor which is what I think bob puts in the kit. The problem is it might cause damage to the edge connector instead. First and foremost clean that edge connector and you should consider replacing the connector to eliminate this problem.
 
Thanks for the help guys. For anyone else looking, I did the following:

- took 1000 grit sand paper wrapped around a metal ruler and sanded the female edge connectors a bit
- used a pick to bow forward any flat looking pins inside the female edge connectors
- cleaned male edge connector (PCB)
- took a mini phillips screw driver and scraped out the insides of the female molex pins
- took a mini flat head screw driver and tweaked the female molex pins so they're a little tighter
- tested voltage between GND and C1+ before plugging PCB back in
- made sure R8 can set and maintain a voltage before plugging the PCB back in

Turned it on and off a few times and now it's been on for an hour with no smoke. Hopefully it's fixed.

Thanks again.
 
Cool. Did you also replace the sense resistors? The +5V might not stay within tolerance unless you do. You could also do the sense mod.


Thanks for the help guys. For anyone else looking, I did the following:

- took 1000 grit sand paper wrapped around a metal ruler and sanded the female edge connectors a bit
- used a pick to bow forward any flat looking pins inside the female edge connectors
- cleaned male edge connector (PCB)
- took a mini phillips screw driver and scraped out the insides of the female molex pins
- took a mini flat head screw driver and tweaked the female molex pins so they're a little tighter
- tested voltage between GND and C1+ before plugging PCB back in
- made sure R8 can set and maintain a voltage before plugging the PCB back in

Turned it on and off a few times and now it's been on for an hour with no smoke. Hopefully it's fixed.

Thanks again.
 
Cool. Did you also replace the sense resistors? The +5V might not stay within tolerance unless you do. You could also do the sense mod.

I would also recommend....just replacing the female side of that connector. When they get to the point of having to scrape them, bending them, etc....they are done. This problem will return (and if he does the sense mod or uses higher ohm resistors.....the next time he might just burn up the fingers on the motherboard instead of a 10 ohm resistor:eek:).

Do all the mods you want......but change that damn connector!

Edward
 
Sanding the terminals is not the long term fix. Once sanded, you are sanding off whatever coating was on them, or left on them, thus building resistance and heat. Replace all terminals, or replace the connector as mentioned.

I removed and replaced just the terminals on my Asteroids...
 
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I would also recommend....just replacing the female side of that connector. When they get to the point of having to scrape them, bending them, etc....they are done. This problem will return (and if he does the sense mod or uses higher ohm resistors.....the next time he might just burn up the fingers on the motherboard instead of a 10 ohm resistor:eek:).

Do all the mods you want......but change that damn connector!

Edward

Agree 100%. But technically, doing the sense mod will mitigate anything from getting burned up. If the edge connector is too damaged / dirty, the +5V will simply droop below tolerance and the game will cease to run (unless you manually crank up the +5V). That's the one plus of doing the sense mod - if stuff starts flaking out, then you know it's time to clean / replace the edge connector again! :D
 
(unless you manually crank up the +5V).

Call me a pessimist, but this is exactly what I invision happening (if it hasn't already happened;)). The amount of work the OP stated he did to that edge connector to make it work.....no way is it going to work realiably for any amount of time.

Edward
 
I replaced R30, but R29 seemed OK.

Still trying to decide how far to take this. Just to be clear, it's not like I did each one of those bullet points and tested after each one and it DIDN'T work. I just kind of shot-gunned it. If you ask me for the one failure point, it's probably in the female edge connector. One of those pins seemed exceptionally flat, and I did notice some oxidation in non contact areas of the pins in there. The PCB edge connectors looked clean.

Could have been the female molex, though, one of the connector pins had it's gap pretty huge.
 
Bob R sells the split pins, if that's what the edge connector uses. I would recommend replacing all of the power and ground related pins. Easy to do. In trying to track down a WTF problem on my Tempest, I repinned the whole connector. Not hard to do.
 
I replaced R30, but R29 seemed OK.

Still trying to decide how far to take this. Just to be clear, it's not like I did each one of those bullet points and tested after each one and it DIDN'T work. I just kind of shot-gunned it. If you ask me for the one failure point, it's probably in the female edge connector. One of those pins seemed exceptionally flat, and I did notice some oxidation in non contact areas of the pins in there. The PCB edge connectors looked clean.

Could have been the female molex, though, one of the connector pins had it's gap pretty huge.

While I agree that replacing the female edge connector is a very good idea, what you've done will probably keep it running reliably for years to come (assuming it's in your gameroom and not left on for extended periods of time). If the game flakes out or the resistor burns up again, replace the connector.
 
I replaced R30, but R29 seemed OK.

Still trying to decide how far to take this. Just to be clear, it's not like I did each one of those bullet points and tested after each one and it DIDN'T work. I just kind of shot-gunned it. If you ask me for the one failure point, it's probably in the female edge connector. One of those pins seemed exceptionally flat, and I did notice some oxidation in non contact areas of the pins in there. The PCB edge connectors looked clean.

Could have been the female molex, though, one of the connector pins had it's gap pretty huge.

Those pins get "weak" from time, heat, and unconnecting/reconnecting.....they lose their spring tension. Once you go bending them, sanding them, descaling them...their spring tension is compromised and should be replaced....not too mention, if a sense resistor is burnt up on the A/R II board.....you've had some descent heat pull through it. Replace and don't worry about it for another 30 years. If they are Molex brand.....you can get away with just replacing the power and ground pins. If it's an Amp brand connector (Atari used both brands)....you're stuck with replacing the entire connector with a Molex brand. The Amp pins are impossible to find (unless you want to order a few thousand).


Edward
 
Once sanded, you are sanding off whatever coating was on them, or left on them, thus building resistance and heat.

Can you explain this? How does removing the oxide layer increase resistance? I'm not trying to pick a fight, I'm just confused. :confused:
 
Can you explain this? How does removing the oxide layer increase resistance? I'm not trying to pick a fight, I'm just confused. :confused:


In addition to sanding off oxidation you may sand off part or all of the outermost layer of the pins. This layer is there to enhance conductivity and once removed reduces the ability of the component to conduct. Additionally sanding can leave the component grooved reducing the contact patch and increasing resistance as well.
 
Can you explain this? How does removing the oxide layer increase resistance? I'm not trying to pick a fight, I'm just confused. :confused:

He likely also removed the passivation layer on the pins which is there to help prevent corrosion. With the bare metal exposed, the pins will corrode and/or rust much quicker.
 
Can you explain this? How does removing the oxide layer increase resistance? I'm not trying to pick a fight, I'm just confused. :confused:

I hear you! No flame taken! Oryk and Bit slicer explained it though... All terminals have a coating, once sanded even to remove oxidation with anything more then a pencil eraser, that can remove the thin down the coating.

The good thing is at least it seems you know the connector and terminals was the issue since you've not had any issues since.
 
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