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Black screen Atari XEGS


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I picked up a broken Atari XEGS on Ebay as a learning project for working on my soldering and desoldering skills. It has a completely black screen with no sign of video or audio activity.

 

The RAM chips were heating up so I replaced those. The RAM chips stopped overheating but other than that there is no change. I still get a completely black screen. The power supply checked out. It seems to be completely fine. It's outputting 5V just like it should. There isn't anything unusual on the motherboard besides my poor job on the RAM chips.

 

What would likely be the culprit here? Is there anything else I can check for or do I just need to start replacing chips?

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What diagnosis tools do you have?

 

Logic probes, oscilloscopes etc can make the job a whole lot easier.

Black screen as it is should at least mean a functioning Antic and GTIA. Antic has to tell GTIA to do VSync, without that the screen would roll.

 

Do you get sometimes different colour or stripes on powerup? Generally the Atari will powerup to a brownish screen fairly regularly. That colour not changing is a good sign that the OS isn't starting up.

 

Turn up the volume on the TV. A click through the speaker on powerup and when you press Reset is a sign that the CPU is working and that the OS is at least getting a start.

 

Next up suggestions I would say are OS, MMU, CPU. If you have game cartridges like Star Raiders or Asteroids then worth a test also. Those games good examples as they run as diag mode so get early control and can give a different sign of life e.g. if the OS Rom is corrupt.

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I don't have any logic probes or oscilloscopes.

 

There's absolutely nothing happening on the screen after I hit the power button. There seems to be no video signal of any kind or sign of any change when I hit power or reset.

 

Well, a logic probe is less than $20 on Amazon. Between that, a multimeter, some schematics and the wealth of information on this forum, I'm 100% confident you can get that system working again. :)

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I had a recent person who said theirs was dead, when I looked at the back of their TV it did NOT have composite video, it only had R G B and none of them doubled as composite... hooked up to a different tv and it was working just fine... flat panels today pffffft

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