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Trying to get a 4 port to work again - only seeing snow


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I have 4 port 5200 that is only displaying snow. The system powers on, and when a game is inserted with and the system powered on, you can see a change in the snow, a little color, but nothing discernible. I have been pouring over posts relating to the same things, first recommendation I came across was to replace the LM393N IC in the switchbox. I ordered up a couple from digi-key and replaced it, no change. The next process I came across was re-seating the chips on the motherboard, I did that and the colors in the snow became a little more vivid, but nothing drastic. Finally, I received a working 2 port and I decided to try swapping out the larger chips (I do not have the schematic, but I know that would include the CPU, GTIA, can't remember the other two offhand), I started one at a time, and with no change swapped all of them at once, still no change. I am sure there is more to do, and perhaps the chips from the 2 port would not work in the 4 port (not sure why that would be), but thought I would come here. So, what should I try next?


Thank you in advance for your help!

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Yes. That's all it is. It handles the power to both sections of the 5200 circuitry- video and logic. Partial failure of this IC can give similar symptoms to having a dead modulator and is easier to replace.

The more I think about it, the more I am leaning towards dead modulator on your system, but would try the IC first.

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