Asteroids Help. Please!

[kentmurphy]

I need some help folks. Purchased an Asteroids last week that has no picture and does not play blind.

I started my troubleshooting by checking all fuses. I noticed both F100 and F101 on the G05-802 deflection board (Issue 5 or 6) were blown. I replaced the fuses and the bridge rectifier (DB100), but when I fired it up both fuses blew again. I then found that the transistors Q708 and Q709 mounted to the chasis were shorted. I replaced both, powered up the cabinet, and the fuse at F700 blew. I decided to do some more checking of the components in the x amplification circuit. I checked diode q708, transistors q707, q706, q705, resistors r718, r721, and found no problems. I replaced the fuse and fired her up. This time no fuses blew but the spot killer led came on and remained on. I did notice that q708 (2n3716) was so hot it could not be touched. I began to suspect that the monitor wasn't the problem.

I switched gears and begin checking voltages with the monitor disconnected. The game boards were not getting +5 VDC. It was about +4.5. In addition, both P1 and P2 stayed lit and there was a loud humming noise coming from the speaker. I adjusted the variable resistor but could only get it to +4.78 VDC. Quick search of the Internet yielded the fix below.

3a. Problem: No video, P1 and P2 stay lit, loud humming noise.

Cause: The 5V supply from the Audio/Reg board was reading about 4.2V.

Fix: Replace the LM305 (Q1) regulator, and readjust the voltage.

Since I can't source an LM305 locally, I decided to hook up my switcher to the test points on the the board to give it +5. Before doing so I removed the J7 connector on the AR board. Now that I was getting +5 to the boards, I began measuring the voltages to the monitor. I did this per the FAQ. Placed the black lead in pin 8 and began cycling through each pin.

Immediately, I detected a problem. With the switcher attached, I measured +26-27 VAC at pins 1, 2, and 3. I also noticed the player 1 and 2 buttons were blinking. I removed the switcher and reconnected the AR board. I measured the voltages with the AR board connected and this time pins 1, 2, and 3 measured about 1.5 VAC.

Now for the questions.

1. Is it acceptable to hook a switcher up to the asteroids board? By doing this did I fry something? I did have the AR board disconnected. Not sure that matters.

2. Anything wrong with measuring voltages the way the FAQ indicates?

3. Why the difference in voltages between switcher and the AR board? Is it because the AR board is not providing the proper voltage? I assume once I rebuild the AR board, I will begin seeing the same +26-27 VAC at pins 1, 2, and 3. Sound right?

4. I have a feeling that my game board needs some work. Does anybody disagree?

5. Anything else I should check?

Thanks,
Kent

 

[Dokert]

Kent,
I would start by looking at the A/R I around R25 and R26 if I remember correctly. One or both may be burnt to a crisp. Rebuild the A/R I, it is cheap to do and you can get the parts from Bob Roberts. Once you have rebuilt the A/R I, then check your voltages before hooking it up to the board.

Your monitor may not even be the issue. I would like to see the game play blind before assuming that there is a monitor issue. I know that you found bad fuses in the monitor, but I would still like to see it play blind first.

 

[vanman]

When ordering your parts from Bob Roberts, I would highly recommend getting his "Big Blue" replacement as well.

My asteroids had blinking P1 and P2, even after I had replaced the big blue and did the AR1 board parts replacement. I ended up having a board issue.

I put the board into test mode, and got a tone pointing to a problem on the board. I sent my board to: mrbill08 and he fixed it both fast and inexpensive for me. It ended up that I think he replaced either one or two ic chips on the board.

Hope this helps,
Chris

 

[kentmurphy]

I agree. I need to get it to play blind first so I decided to go back to basics and measure the voltages at J5 on the power brick.

http://webpages.charter.net/kentmurphy/images/asteroids/powerbrickwire.jpg

I am pretty sure I found some problems.

Pin 1 read 12.8vdc. Expected voltage was 10.3vdc. Good
Pin 2 read 13vdc. Expected voltage was 10.3vdc. Good
Pin 3 read 13.1vdc. Expected voltage was 10.3vdc. Good
Pin 6 read 18.8vac. Expected voltage was 36vac. Bad
Pin 7 read 18.8vac. Expected voltage was 36vac. Bad
Pin 8 read 1.3vac. Expected voltage was 6.3vac. Bad
Pin 9 read 6.3vac. Expected voltage was 6.3vac. Good
Pin 11 read 30vac. Expected voltage was 65vac. Bad
Pin 13 read 26vac. Expected voltage was 65vac. Bad

I took a few more measurements to validate my suspicion.

First, I took a measurement at the terminal block (TB1). I touched one lead to screw 1 and the other to screw 2. I got a 123vac. This tells me that there is no problem with the ac line cord, line filter, and switches.

Next, I put one lead in the pin 4 of the J5 connector and then touched the other lead to each side of the fuse block. All AC voltages read as indicated above. Not sure this makes sense, but I wanted to validate that there was not an issue with the fuse block and it appears there wasn't.

I now suspect that I have a bad transformer. Would you agree? Is there anything else I should check? It does appear that something has leaked out of the transformer and stained the bottom of the cabinet. Does this indicate a bad transformer?

Thanks,
Kent

 

[Dokert]

I do not agree. I believe that you may have taken the AC readings incorrectly. Please verify as follows...
red lead to pin 6
black lead to pin 7
36vac expected

red lead to pin 8
black lead to pin 9
6.3vac expected

red lead to pin 11
black lead to pin 13
65vac expected

Pins 1, 2, 3 are unregulated and within tolerance.

 

[kentmurphy]

Good call Dokert! Yes I did take the readings incorrectly. I left the black lead in pin 5 for all readings. I should know better.

Just finished taking new readings.

Pins 6 & 7 read 37.3vac
Pins 8 & 9 read 7vac
Pins 11 & 13 read 62.7vac

These appear to be within tolerance. Would you agree?

Thanks,
Kent

 

[Maxstang]

This is gonna sound dumb, but a bad pokey chip can cause the flashing 1 and 2 start buttons as well as a bunch of other symptoms including no game play. If you have a pokey handy, try switching it out and see what happens. I also assume you've reseated all your socketed chips as well? -M

 

[Dokert]

Good call Dokert! Yes I did take the readings incorrectly. I left the black lead in pin 5 for all readings. I should know better.

Just finished taking new readings.

Pins 6 & 7 read 37.3vac
Pins 8 & 9 read 7vac
Pins 11 & 13 read 62.7vac

These appear to be within tolerance. Would you agree?

Thanks,
Kent

Much better Brother, looks good to go. Test what is coming off of the A/R I now and see what you get. Remember that you will get nothing on the +/- sense pins.

 

[kentmurphy]

Thanks Dokert. I took these readings once before, but I plan on rechecking this evening. I will post my results.

Kent

 

[kentmurphy]

Ok. Here are my readings from the ARI board

10.3vdc = 11.4vdc = good
5vdc = 5.54vdc = good

I also checked the game boards.

+5vdc = +5.3vdc = good

I dialed this back to +5vdc by adjusting the variable resistor on the ARI board.

Now I am getting both P1 & P2 lights blinking.

What should be next step? I am guessing I should measure ac voltages going to the monitor per the B&W vector FAQ. Would you agree?

Thanks,
Kent

 

[kentmurphy]

One more comment. I had previously measured votlages going to the game board and I was only getting +4.7vdc. This is as high I could get it even with adjusting the variable resistor. I did replace a burnt diode (1n4001) on the board, but after doing this I was still not getting +5vdc. It seems as if all the disconnecting and reconnecting of connectors has now given me the right voltage at the game board. Very strange.

Thanks
Kent

 

[ELutz]

Here are my readings from the ARI board
5vdc = 5.54vdc = good

I also checked the game boards.
+5vdc = +5.3vdc = good

That a pretty descent size voltage drop....almost a 1/4 volt. You might want to check your connectors (probably the motherboard edge connector).

This isn't your problem, now.....but, down the road, it will be.

Edward

 

[kentmurphy]

Thanks Elutz.

The saga continues.

Note all tests below were done with the test switch on.

First, I decided to take more ac voltage readings at the Molex connector that connects to the monitor. Again the readings were lower, but after closer inspection I realized the FAQ pin-out does not match what's on the asteroids wiring diagram. The asteroids wiring diagram is correct. I am now confused on how to validate that the monitor is getting good signals from the game boards. Can anyone help?

http://webpages.charter.net/kentmurphy/images/asteroids/xyfaqpinout.jpg
http://webpages.charter.net/kentmurphy/images/asteroids/wiringdiagram1.jpg

Since I was getting +5vdc to the boards, I decided to hook-up the monitor and turn it on. Immediately q708 got hot again. I decided to remove the screws and replace the mica insulator behind q708. Fired the machine back up and q708 did not get hot. Apparently it was shorted to the chassis?????

I turned up the contrast / brightness and saw two dots connected by a vertical line. I guess this means my monitor is ok. Correct?

Next I noticed both P1 & P2 were lit. I was able to push each button and get a high pitched sound, but I did not hear the other tones indicating RAM failure. Sounds like a bad game board. Correct?

Thanks,
Kent

 

[Dokert]

Ok. Here are my readings from the ARI board

10.3vdc = 11.4vdc = good
5vdc = 5.54vdc = good

I also checked the game boards.

+5vdc = +5.3vdc = good

I dialed this back to +5vdc by adjusting the variable resistor on the ARI board.

Now I am getting both P1 & P2 lights blinking.

What should be next step? I am guessing I should measure ac voltages going to the monitor per the B&W vector FAQ. Would you agree?

Thanks,
Kent

Kent, 5.54 and 5.3 is NOT good. You need to dial it down, it should be no more than 5.1 on the board. If I remember right 4.9 to 5.1 is considered "Good".

The 11.4 is okay, because it is unregulated.

Wouldn't hurt to measure the AC going into the monitor. I would expect it to read the same as pin 11 to pin 13 which was around 65vac I think. Don't know, the scat is not sitting right in front of me at the moment.

 

[Dokert]

Thought I suggested that the trans was shorted to the chassis, when you said it got smoking hot.

With your contrast and brightness up, put it in test and see what you get.

Check the swing out of the X/Y going to the monitor. I don't remember which T-shooting guide has it in there. Might be in the Asteroids scat package.

 

[modessitt]

With this monitor, I'd reflow all the connector solder joints, and replace the transistors regardless, as well as replacing any caps on the boards. Might as well eliminate potential problems later...

 

[Dokert]

Hey Mod, sounds like he actually has one axis to me. Your thoughts?

 

[kentmurphy]

Kent, 5.54 and 5.3 is NOT good. You need to dial it down, it should be no more than 5.1 on the board. If I remember right 4.9 to 5.1 is considered "Good".

Ok when I dial the voltage back to +5vdc on the ARI, I only get +4.78vdc at the boards. As you indicated, don't I want at least +4.9vdc at the boards? Does it really matter what the voltage is at the ARI as long as the boards are getting +5vdc?

Wouldn't hurt to measure the AC going into the monitor. I would expect it to read the same as pin 11 to pin 13 which was around 65vac I think. Don't know, the scat is not sitting right in front of me at the moment.

Can you give me some guidance on checking the voltages going to the monitor? The FAQ seems to be out of whack.

Thanks,
Kent

 

[modessitt]

Check the connectors from the transistors to the deflection PCB. Wiggle them to see if the entire picture comes up (turn brightness up so you can see the line faintly). if wiggling fixes the picture, pull the deflection chassis and repair the bad solder joints/burnt connector.

I had an asteroids deluxe with issues like this and they were fixed by replacing the deflection transistors on the heat sink...

 

[Dokert]

You want 4.9 to 5.1 at the board, give me a couple of minutes to look up the monitor info.