On this particular repair, I had an issue where certain parts of the screen would show diagonal bars, but of two interlaced colors from nearby on the screen. Almost like the colors got slightly mixed up in the signal.
it’s kinda tough to see, but just above the Yoshi coin here in SMW, you can see some dark green striping.
This was on an older SHVC board, and swapping the video encoder chip actually fixed this! Here’s the old and new chips:
After that, the composite video signal was pretty clean, but I noticed a really similar effect over RF:
I went a little nuts – installing a capacitor over the 5V regulator and even boosting the capacitor on the encoder chip to 10uf from 1uf. I tried different cables, unplugging everything but the TV to cut interference – the weird color glitch was still there.
Finally, I tried another TV – and the issue wasn’t there. Apparently the little TV I use for testing was having trouble properly decoding the chroma signal out of the RF output. Super weird, but hey, glad it wasn’t the CPU! 😂
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