Asteroids Deluxe with Odd Automatic Start Issue

Samelak

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My Asteroids Deluxe developed an odd issue when I power up the cabinet it automatically starts a 2-player game. I thought it might be a short on the 2-player switch, but I swapped with the 1-player and even disconnected both start switches and it still occurred. I also have a Multi-Asteroids chip installed. Any suggestions?
 
There are small resistor-capacitor networks connected to the inputs, before the go into the actual input IC's. Frequently on these Atari games, the caps will either go bad, or get cracked/broken (as they are often the glass-encased type). I just repaired a Tempest myself with the exact issue (except it was on one of the coin switches).

The first thing, if you have ruled out the wiring, to do would be find which cap corresponds to that input (in the schematics). You can try measuring with a DMM across it, and comparing to the other caps near it, for the other inputs, and seeing if it is any lower, as they will become on the order of a few hundred ohms when they go bad.

If it is low, you can remove the cap, which will temporarily fix the issue. But you should replace it longer term. It's a 0.1uF 50V axial cap. The replacement does not need to be the same glass type. I get them from Great Plains Electronics, but anyplace will have them.

If it's not the cap, it may be the input IC that it's connected to (which may have a stuck output), but the cap is more likely.
 
I had a little bit time to mess with it, but I have no idea how to do what you said Andrew. Beyond my knowledge. I tried disconnecting the P2 switch altogether and it still auto starts. Now what is really strange is that it will auto start about 5 games in a row and then all of a sudden it goes back to normal (I have to press start to play). I also noticed I still have the big blue installed so I am wondering if I am getting bad voltage. I need to measure that next. I'm still going to order a new big blue regardless of the issue.
 
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I had a little bit time to mess with it, but I have no idea how to do what you said Andrew. Beyond my knowledge. I tried disconnecting the P2 switch altogether and it still auto starts. Now what is really strange is that it will auto start about 5 games in a row and then all of a sudden it goes back to normal (I have to press start to play). I also noticed I still have the big blue installed so I am wondering if I am getting bad voltage. I need to measure that next. I'm still going to order a new big blue regardless of the issue.


It's unlikely to be your big blue. To test the BB, measure the AC voltage on the 10.3V DC test point. If it's under 0.500V AC, your big blue is fine.

The issue will still happen with the start button unplugged, because the issue that is tripping the signal is on the game board itself. It's either the resistor-capacitor network on the input, or the input chip itself.


Find capacitor C65, and desolder and lift one leg of it, and see if that fixes it. You don't need to remove the cap entirely, just lift one leg of it. Either leg is fine.
 
I'll give that a shot and post the results. BTW...the Tempest cabaret is still running strong. Just a shame I suck at it.
 
Bingo! That was it. I have one of the legs off and it now works correctly. So I can use regular caps instead of the little glass type? How do I know which side is positive since it's not marked? I noticed there are four of these caps sharing a trace on one side and the other side have their own trace. Thanks for the help and would like to now how you where able figure it out so I can have a better understanding.
 
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It's not an electrolytic, so it likely isn't polarized. If it is ceramic or glass, it generally isn't polarized.
 
Those caps aren't polarized like electrolytics. Any 0.1 uF will do, and the new ones are not glass, but they'll be fine. You can install it either way.

It's a semi common issue on Atari boards. I've seen it several times before.

The caps get resistive when they go bad, and pull the voltage down, so it looks like the switch is being pressed when it isn't.
 
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I found the caps on Great Plains like you said, but they are currently shut down for being sick. How long can I safely play without replacing?
 
You can try Mouser, DigiKey, or Allied. They should all have the same things, and a lot bigger staff.
 
You can get one anywhere, as they're pretty common. You could even steal one from a junk board, as most boards use 0.1's all over them as decoupling caps.

It isn't a critical part. It's just there to de-bounce the input. You can play without it, and it won't damage anything.
 
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