Rebuilt AR producing 6 volts

Cmiller

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Picked up an Asteroids. I disconnected the PCB to see what the power supply was producing. The AR was putting out 6 volts. I tried turning down the adjustment pot, but it only dropped to 5.7. So, I ordered a rebuild kit and installed it. I was disappointed to see it was doing exactly the same thing. What should I try next?
 
Asteroids AR's are different than all others, in that they have diodes in place of the two sense resistors found on the later versions. This difference makes the AR read artificially high when there is no load on the 5V line (e.g., when the game board is not plugged in). This behavior is normal for Asteroids AR's.

Set the AR to about 6.2V without the game board plugged in, and once you plug the game board in, the voltage on the game board will measure around 5.0V (though you should still measure and adjust to 5.00V, as measured using the 5V and GND test points on the game board, not the AR.)
 
Thanks for the reply. I will do that this weekend. I was worried because I have another Asteroids (same model AR), but it shows 5 volts without the PCB connected (and the game works). I will take a look at what I'm getting on the game board on that machine. I may be getting lucky that I'm getting just enough power there.

I believe you repair vector chassis, right? I may be sending you my G05 after I give it one more try.

Thanks again, Chris
 
Thanks for the reply. I will do that this weekend. I was worried because I have another Asteroids (same model AR), but it shows 5 volts without the PCB connected (and the game works). I will take a look at what I'm getting on the game board on that machine. I may be getting lucky that I'm getting just enough power there.

I believe you repair vector chassis, right? I may be sending you my G05 after I give it one more try.

Thanks again, Chris


Look at your AR. There are two locations, one in the upper left (furthest from the heatsink, near the connectors), and another below the 8-legged LM305 tin can-looking part, where on the AR that produces 6V, you will see diodes in those two locations. On the other AR that makes 5V, those two spots likely have resistors in them.

The AR-I-01's used on Asteroids came with diodes from the factory. But some operators changed them BITD to resistors, so the voltage will measure more accurately with no load. The tradeoff is that if either the 5V or GND lines get interrupted or broken between the AR and the game board (e.g., by a dirty edge connector, or having it not on all the way), those resistors will burn up (which is what happens on the later-model AR's, which all have resistors instead of diodes in those two spots). You can replace the resistors, as they are just 10 ohm 1/4 watt ones, but when you have the diodes in there, they will not burn up if one of the lines is broken.

In the end, it doesn't matter which you have in there, as long as you know that the voltage will be artificially high if you have the diodes.

And yes, I repair all Atari vector game boards and monitors. PM me anytime for info.
 
Look at your AR. There are two locations, one in the upper left (furthest from the heatsink, near the connectors), and another below the 8-legged LM305 tin can-looking part, where on the AR that produces 6V, you will see diodes in those two locations. On the other AR that makes 5V, those two spots likely have resistors in them.



The AR-I-01's used on Asteroids came with diodes from the factory. But some operators changed them BITD to resistors, so the voltage will measure more accurately with no load. The tradeoff is that if either the 5V or GND lines get interrupted or broken between the AR and the game board (e.g., by a dirty edge connector, or having it not on all the way), those resistors will burn up (which is what happens on the later-model AR's, which all have resistors instead of diodes in those two spots). You can replace the resistors, as they are just 10 ohm 1/4 watt ones, but when you have the diodes in there, they will not burn up if one of the lines is broken.



In the end, it doesn't matter which you have in there, as long as you know that the voltage will be artificially high if you have the diodes.



And yes, I repair all Atari vector game boards and monitors. PM me anytime for info.



You were right! I checked the locations you mentioned and found that:
(a) there were diodes on the board putting out 6 volts and
(b) bridged connections [no resistors] on the board putting out 5 volts.
I never looked closely at the board putting out 5 volts since it was working.

If it was your AR board, would you replace the bridges with resistors or diodes?

Thanks so much for the guidance!
Chris
 
Ok, then someone did the 'sense mod' on the one where they bridged the connections to bypass those diodes. It's a hack that some ops would do to try to 'fix' other power related issues, by bypassing the feedback that helps the AR regulate the voltage. I would recommend removing that and restoring the AR to original condition.

I try to restore AR's to original condition, mainly for historic purposes, as well as consistency. Technically you could use diodes or resistors in any AR, but I only use the diodes in the Asteroids ones, so people will know what to expect. (As I always remind folks about the higher voltage issue when they buy or get Asteroids AR's from me.)H
 
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