I got inspired but many repair videos especially tronicsfix and recently decided to try it myself. I was quite successful in repairing a few switches I got from ebay but I’m now clueless with one of them:
At the start it did not display anything on the screen or when it was docked. I discovered a bend pin in the lcd connector, which led me to replace the connector and now the display works and shows the nintendo symbol for 2 seconds and goes dark afterwards. It does not seam to shutdown completely since I can hear a hissing sound from (I guess the speakers) until it goes silent when I press the power-button for several seconds.
I checked for shorts and took diode mode readings all over the board (e.g. M92, CPU, PI3) and compared them to a known good switch and the values in other topics, but I wasn’t able to find anything suspicious.
The switch charges normally and also jumps into fast charge.
I checked the voltages on various testpoints that I found in other topics but everything matched up as far as I can tell.
With the help of a repurposed Joy-Con-Slider I managed to put the Switch in RCM mode, it was detected by my computer but I got no response when I tried to inject a payload, neither the 0x0000 nor the 0x7000 answer.
I read that emmc could be the wrong one or defective but popping it off and trying to inject a payload yielded the same results as above.
I would be fantastic if somebody could give me a hint what I could try next, help would be very much appreciated.