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jschaap26

Black screen and the screech of death...

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I've got a 99/4A that when powered on outputs black video sustained screech when turned on. I've seen other post about this same problem and have tried what I believe are all the simple fixes including:

 

- Checking the power supply (I've tested the voltages and it's confirmed working for two other 99's)

- Removing the cartridge connector

- Reseating all the sockets chips

- Looking for anything on the board that is damaged

 

I had a spare 9918A and swapping that in but got the same results. I have a logic probe and could run tests (if given VERY specific instructions) but no soldering skills. Thanks in advance for your insights.

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The BSOD can be caused by a variety of bad chips including: VDP, CPU, RAM (16k), RAM (256b), ROM, GROM.  There is a 3 part series on YouTube, in which a guy repairs his:

 

The problem with his TI was the CPU, but that doesn't mean that yours has the same problem.

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Personally I'd start by replacing the two MCM6810 RAMs, but you need at least some level of soldering skills to do it.

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I know how you feel. My Beige TI has the same symptoms, but attempting to repair it is too complicated as there are way too many failure points.

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