Asteroids playing blind

Jr. Pac

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So this Asteroids used to be rock solid before we moved cross-country. I bought it a few years ago off @Slackmoe who I believe put quite a bit of work into it.
Powered it up for the first time today since the move and it plays blind.
  • Game behaves normally except for no picture on screen
  • Neck glow and monitor noise present
  • LED on monitor board does not light up at all except for a split second while powering off
  • Brightness and contrast dials do nothing
  • The two monitor fuses and five on the power block confirmed fine
  • Reseated all connectors
Whatever happened must have happened during transit. I did accidentally leave the manual in the coin box and it ended up on the floor of the cab, but I can't imagine that did anything.
Everything looks fine to my eyes, but I'm not familiar with Atari cabs or vector monitors.

Any pointers would be greatly appreciated. Thanks in advance!
 

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Last edited:
Do you have an oscilloscope? If you do, connect it in X-Y mode to the X and Y output (and ground) and see if you get an image.

You see an image: Something is wrong with your CRT.

You don't see an image: Something is wrong with your game board.
 
Do you have an oscilloscope? If you do, connect it in X-Y mode to the X and Y output (and ground) and see if you get an image.
I do not unfortunately—only have a logic probe and a multimeter.
Might be time to invest in one?
 
I do not unfortunately—only have a logic probe and a multimeter.
Might be time to invest in one?
You live in California. There is probably someone close to you who may be willing to help with a scope.

If you love vector games, an oscilloscope is pretty essential. You might find one for a good price on craigslist or facebook.

20 mhz is good enough for vectors, it should have an X-Y mode button ideally, and you set to 2 volts / division. You can look up my "The Asteroids Log" thread and see the images you get.
 
You live in California. There is probably someone close to you who may be willing to help with a scope.

If you love vector games, an oscilloscope is pretty essential. You might find one for a good price on craigslist or facebook.

20 mhz is good enough for vectors, it should have an X-Y mode button ideally, and you set to 2 volts / division. You can look up my "The Asteroids Log" thread and see the images you get.
Thanks for the info! Actually live in Kansas City area now but can't find where to edit location on here.
 
Seems the spot killer (on monitor board) is telling you there are vectors being inputted from the logic board. (ie. momentarily on then off - that's good).
My guess is you have no high-voltage. Do you hear "crackle" when staring up? Can you feel static on the FRONT of the tube? Do you have a HV probe?
Did you check the connections to the HV cage? Did you check the anode wiring into the CRT?

Did you read the monitor FAQ?

 
Press and hold the reset button on the game board while looking VERY closely at the spot killer LED on the deflection board.

Does the LED light up at all while reset is pressed? And does it go off when you release reset?

Note that the LEDs on these 801's are very dim. So you have to look very closely to see if it lights.
 
the thing is you can guess or know where your problem is. you need a scope to check the output for sure and not guess. @andrewb has given you good advice for a preliminary idea of where the problem is but the safer and surer method is disconnect the monitor and check signal output. the good news is that the game is playing blind so that you have a working game up to the point where the counters come into play and your problem is in an easy location from the counters to and including the monitor, you just don't want to overdrive the monitor so don't leave it fully running with an unconfirmed output longer then necessary to verify something
 
If the spot killer test above works (and behaves as described, turning on and then off again when reset is held and then released), that means the game board is generating valid XY signaling, and the deflection system of the monitor is working. The spot killer is pretty picky, and will only turn off when the deflection system is functioning properly, and the game board is outputting valid XY signaling. So that one test tells you that 2 aspects of the game are ok, if the LED behavior is correct.

If the LED behavior isn't correct, then we'd need to dig deeper, starting with the game board. But do that check first and post here, then we'll proceed with next steps.

Diagnosing a vector game problem is like diagnosing a gasoline engine. Generally speaking, engines need three things to work: Fuel, spark, and air. If an engine isn't working, you start by verifying each of those 3 things.

For vector monitors it's similar, except you need 4 things: Good XY voltages from the game board, a working deflection system, neck glow, and HV. If a game isn't working, one of those things isn't right. The spot killer can verify two of them at once, if they are ok. Your eyes can tell you if you have neck glow. And an HV probe will tell you if you have HV or not.
 
If the spot killer test above works (and behaves as described, turning on and then off again when reset is held and then released), that means the game board is generating valid XY signaling, and the deflection system of the monitor is working. The spot killer is pretty picky, and will only turn off when the deflection system is functioning properly, and the game board is outputting valid XY signaling. So that one test tells you that 2 aspects of the game are ok, if the LED behavior is correct.

If the LED behavior isn't correct, then we'd need to dig deeper, starting with the game board. But do that check first and post here, then we'll proceed with next steps.

Diagnosing a vector game problem is like diagnosing a gasoline engine. Generally speaking, engines need three things to work: Fuel, spark, and air. If an engine isn't working, you start by verifying each of those 3 things.

For vector monitors it's similar, except you need 4 things: Good XY voltages from the game board, a working deflection system, neck glow, and HV. If a game isn't working, one of those things isn't right. The spot killer can verify two of them at once, if they are ok. Your eyes can tell you if you have neck glow. And an HV probe will tell you if you have HV or not.
Thank you! The LED indeed turns on while holding "reset" and turns off as soon as it's released. So that narrows it down to HV?
 
Thank you! The LED indeed turns on while holding "reset" and turns off as soon as it's released. So that narrows it down to HV?


Yes.

The main issue with 801's when there is no HV, is the HV doubler can be bad. 802's and v2000's have a diode after the flyback, which rectifies the AC HV to DC HV that drives the tube.

801's have something similar, but in addition to rectifying the AC, it also doubles the voltage of the final output HV. There is a circuit with two diodes and one cap that does this. The problem is that unlike 802/v2000's, where you can access and replace the diodes if they fail, the ones on 801's are potted into the voltage doubler block, which is the big block of epoxy mounted inside the HV.

When the doublers are bad, you need to rebuild a replacement by hand, and pot it in epoxy. I've done a few, they take a bit of work to get right.

However, we may be putting the cart ahead of the horse here. Do you have an HV probe? If not, you're going to need one, for any of this. I would check to see if/what HV you're getting now, as that's more information. There are other things we can check once you can get a probe, to know if any other changes we try, make a difference.
 
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