Asteroids - HS Electrical Project - Help

dyrwolf

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Have an asteroids cocktail table as a vocational high school project. Not sure where to start, but here is current status.

1. No image. Red LED lit on monitor card. Also red LED lit on MPU board.

2. No game play without image. There is a buzz/beep when any button in pressed, no other sounds.

3. Checked voltages, and the 36 volt on the power supply reads 18v. These are red wires on the J5 connector. These wires trace to the MPU board, so it is not getting the power it needs?

Bad transformer? Seems like the 2 red wires are low by 1/2 coming out of the transformer. There does not seem to be any damage to the transformer.

Any suggestions?
 
1. Led on monitor means spot killer, meaning it isn't seeing a video signal. Not the end of the world since the monitor prob just needs all the connectors resoldered. Very common problem. Also look for blown fuses on the monitor board as well.

See here for what to look for (any molex connector on the monitor pcb should be resoldered)
http://www.junknet.net/arcade/?g2_itemId=3339

2. Sounds like it's in test mode. Should be a self-test switch mounted on a plate near the coin accepter. Its shown in this pic: http://www.junknet.net/arcade/?g2_itemId=3319&g2_imageViewsIndex=1

3. If you tested this, in AC mode, from the red wires to ground, then thats why you're only seeing half the voltage. The 36v is if you test across both red wires. Check the fuses on the power brick anyway, but I think you're fine.
 
Have an asteroids cocktail table as a vocational high school project. Not sure where to start, but here is current status.

1. No image. Red LED lit on monitor card.

Spot Killer - monitor is not getting required signal from gameboard

Also red LED lit on MPU board.

indicates the presence of +5vdc to the game board

2. No game play without image. There is a buzz/beep when any button in pressed, no other sounds.

Game board error sounds

3. Checked voltages, and the 36 volt on the power supply reads 18v. These are red wires on the J5 connector. These wires trace to the MPU board, so it is not getting the power it needs?

You measured the voltage incorrectly. Set your meter for 200vac, put one lead in J5 pin 8 and the other lead in J5 pin 9

Bad transformer? Seems like the 2 red wires are low by 1/2 coming out of the transformer. There does not seem to be any damage to the transformer.

Any suggestions?

Read above in the bold Got an O-scope?


;)
 
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We have plenty of Oscilliscopes in the school.

I am going to check the self test switch tomorrow. Tell the student doing this the right way to check the 36v, and take a look at the solders on the Monitor boards. I ordered a fix kit for the monitor. Figured it would not hurt, and was only a few bucks.

Thanks for input
 
2. No game play without image. There is a buzz/beep when any button in pressed, no other sounds.

Game board error sounds

"WHEN ANY BUTTON IS PRESSED" - Sounds like it might be in test mode.

Check for a test mode switch inside the coin door.
Are the Player 1 and Player 2 select buttons lit up solid?

EDIT: Duh, I just saw that Orion3311 mentioned the test switch already ......
 
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We have plenty of Oscilliscopes in the school.

I am going to check the self test switch tomorrow. Tell the student doing this the right way to check the 36v, and take a look at the solders on the Monitor boards. I ordered a fix kit for the monitor. Figured it would not hurt, and was only a few bucks.

Thanks for input

You can hook an O-scope to the X and Y out on the game board. If the game board is working, you will see the game on the O-scope. If the game is in test, you will see the test screen on the O-scope.
 
So, is the project to just make the game work, or to actually learn something about how these games work, what each section does, and how to do repairs on them?

If the latter, then just have them do everything. Start with a full rebuild of the power brick, then a rebuild of the ARI, show them how to pull, clean, and replace chips properly, full rebuild of the monitor, testing and repairing the marquee light, replace the line cord (if necessary), go through the coin door, check the speaker and volume control, check function of the control panel buttons and clean/adjust contacts, do cosmetic repairs, etc. Once you do all of that, the game should work fine...
 
Depends on how the student takes to it. I am a science teacher and I have a bunch of these games in my basement and they do not work. If we get it working, the students involved will learn some stuff, for sure. It's a vocational school, and this is the electrical tech class.
 
Well, moved the test switch into up position, and the game played.

However, connected XY out of game board to oscilliscope, and got nothing. We did this by seperating the connector going to the monitor, and jumping, with alligator clips, to the scope. I think it was a yellow and orange wire.

Does the XY ground need to go to scope too?

Any pointer on settings I should use on the scope? We were unsure exactly how to use the scope, so there could have been a signal, but we did not have scope setting right?

Thanks in advance for any info.
 
The game board itself has X-OUT and Y-OUT lugs. And a GND lug. That's where you should test it. The wiring or edge connector could be problematic...
 
The game board itself has X-OUT and Y-OUT lugs. And a GND lug. That's where you should test it. The wiring or edge connector could be problematic...

Agreed.

Take the X probe and clip it to the X - out on the board, take the Y probe and clip it to the Y - out on the board. Set scope for X-Y operation and see what you get. The voltage setting on the scope should be pretty low IIRC 1v or .1v.
 
Most scopes have 2 channels, 1/x and 2/y, so each signal (x and y) have to be connected to their respective channels. The gnd has to go to one of the grounds. Each channel should be set for DC input, and I've used 1v/div on both channels.

Then there's the Z channel that if the scope takes it, is usually on the back. Thats the brightness. Again you only need the xy ground from the game hooked up to one of the grounds on the scope since they're all shared anyway.

Then you have to put the scope in x-y mode. On my newer BK Precision, there's a pushbutton for it. On my old junky Tenma, I have to crank the time/div knob fully clockwise. You should be able to tell, as with the game off, you should only get a single dot on the screen. Turn the brightness down a bit so you don't burn the tube on the scope, and when you turn the game on...you should see it on the screen, but it'll be a little funky since the scope doesn't do blanking...you'll see a retrace line connecting all the objects lol.

Once you get the game picture up on the screen, you can use the x-y size pots on the game board to adjust to the scope screen, or use the fine voltage adjustments on each channel on the scope. I'd use the scopes adjustments if you can since the game board should already be tuned to the real monitor.

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We tried the oscilliscope. Hooked tests leads to the x out, y out, z out, and gnd test loops (for lack of a better word, but little loops of metal on the mother board labeled), and got nothing on the scope. The scope was set for both channels, (x being an input for one channel, y for the other), and we had a single dot moving across the screen (same whether game on or not). We hear the game play, but no change to the scope.

We are going to try a different brand/model of scope next week, but any ideas if the game plays (from sounds) but no image output from board?

Thanks
 
If you have normal game sounds when play is pressed it is playing blind. If it is playing blind, you have a monitor issue. Also if it is playing blind, hooking it up to an O-scope will let you see the video.
 
We tried the oscilliscope. Hooked tests leads to the x out, y out, z out, and gnd test loops (for lack of a better word, but little loops of metal on the mother board labeled), and got nothing on the scope. The scope was set for both channels, (x being an input for one channel, y for the other), and we had a single dot moving across the screen (same whether game on or not). We hear the game play, but no change to the scope.

We are going to try a different brand/model of scope next week, but any ideas if the game plays (from sounds) but no image output from board?

Thanks

Could be that you don't have the volts/div set correct IIRC .2 V/D will work. The scope needs XY mode on the Time/Div set.

You may have already done this, but check that you have +- 15V if one or both is bad, you won't have video out.

A quick check with a DMM is to put it in AC mode and check the AC volts on the Y output lug, and the X output lug. You should read around 2.5-3.5 Vac If you are in that range then your video out should be working, and you should be able to get a picture on an xy scope.

If not then you need to back track through the video circuit.

I start by checking the input pins on the DAC to make sure they are getting signals. Then check the outputs of each opamp stages, and the switches.
Best to do that with a scope. So you can see the output.
 
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