Tempest playing blind...or almost blind. But monitor is fine.

jehuie

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Tempest playing blind...or almost blind. But monitor is fine.

I rebuilt the monitor in my Tempest Cabaret and it looked like it was playing blind at first. But then I noticed I sometimes was getting tiny vectors near the center of the screen if I turned the brightness up. But spot killer was flickering a lot.

I moved the monitor to a known working Tempest and it looked great. So the monitor is good now.

I went through and resoldered all the header pins on the connector between the two boards and re-seated all the socketed chips and tried it in my working Tempest cab. But it still was doing the same thing.

Mostly there's just no image at all. Are there common culprits for something like this or do I just need to start at the beginning and try to troubleshoot the cpu board? I hate troubleshooting cpu boards most of all. :)

Thanks.
 
What I'm really wondering is if there are common parts that could be bad that I can just swap out from my working board. Thanks.
 
Check for the proper voltages to the board. If you're missing the +/- voltages to the analog part of the video output or if they are too low then you'll have odd video issues.
 
Tempest doesn't have an AVG chip...

Thanks....I was scratching my head looking for it! :)

I'm heading out to there to work on it a bit. I think I'm going to start by just swapping out the working aux board, cpu board and interconnect cables to see which one is the problem child.
 
Ok....swapped everything around and it's definitely the main CPU board that's the problem The cable is good and the aux board is good.

Since it plays blind I'm assuming there's a problem in the video section of the board. I look at it and it looks like a bunch of random components to me.

Anyone know of a good document out there that's good for helping to track this thing down? I've got a meter and a logic probe but that's like the most sophisticated equipment I have!
 
You need an oscope to look at the video section properly. It could be anything from a missing bit going into the dac, to a bad lf13201 switch, or even a bad mc1395.

It will be hard to say until you can put a scope on the outputs and check the wave forms.

You can start by checking the ac voltage of the x and y outputs. They may help you narrow it down to either x or y. It could still be before the output stages.
 
You need an oscope to look at the video section properly. It could be anything from a missing bit going into the dac, to a bad lf13201 switch, or even a bad mc1395.

It will be hard to say until you can put a scope on the outputs and check the wave forms.

You can start by checking the ac voltage of the x and y outputs. They may help you narrow it down to either x or y. It could still be before the output stages.

Yeah, no scope here or knowledge of how to use it. However, I did just check the X and Y outputs since I found that in a troubleshooting guide. My meter is digital so I don't know if it can pick up a swing. But the voltages don't seem right in any case. I'm getting +9.5 on the Y out and -9 on the X out.

Does that mean anything to you?
 
Well that does show it's a board problem.

I would check the simple things first. Broken legs on the adjustment pots, or bad pots.

Make sure you have the +-15v, and 6.8v

Then you might try measuring the voltages coming out of A11 pin 1, and D11 pin 1. Should be around 4vac, or 2vdc. Can't recall.
 
Well that does show it's a board problem.

I would check the simple things first. Broken legs on the adjustment pots, or bad pots.

Make sure you have the +-15v, and 6.8v

Then you might try measuring the voltages coming out of A11 pin 1, and D11 pin 1. Should be around 4vac, or 2vdc. Can't recall.

Thanks...ok I'm baffled. I had to put the game away for a bit so I tossed the back door on and pushed it up against the wall and left. When I came back out, I looked over and...not only had I inadvertently powered the game up by putting the back on....but it was also working. Strange. Any ideas why this would happen?
 
Most likely case is a connector/cable problem.

Edge connector perhaps? I tried the board in 2 different cabs and it was dead in both. The edge connectors on the board itself look clean to me. And I replaced the interconnect cable as well with the same results. Or is there another one you mean?
 
Did you reseat the socketed chips or clean their legs. I'll bet it's something along those lines...
 
Did you reseat the socketed chips or clean their legs. I'll bet it's something along those lines...

I pulled each chip and inspected them all. They looked very clean so I didn't clean them up. So I replaced them.

It's consistent....when I power up it's dead and spot killer comes on. Let it sit for a while (15 or 20 minutes) and come back and it's working just fine. Weird. Bad socket perhaps that heats up and then makes contact?
 
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