Signal 4 short to VCC

Hi all

I've been trying to get my board (the old, red, sparkfun one) to listen to my receiver but CH 4 doesn't move. Testing it with a multimeter, I found that the 4 IN pin is being shorted to the VCC. I'm assuming this is the reason reading the receiver signal doesn't work. For the life of me, I can't see where the short might be. All of my solder connections are clean, so even though that's the most likely explanation I'm searching for the another reason before I start ripping them apart. Could it be that this has something to do with the MUX? If anyone has suggestions or experienced something similar, any help would be appreciated. Or if someone has an unsoldered pin 4, could they check if the Ch. 4 IN or the 3rd pin down on the right of the multiplexer chip is shorted to VCC on theirs?


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  • David,

    I measured the voltage in the CH4 IN pins ( a soldered board ready to 2.7.1 with rudder control) and got GND/5V/0V .

    in the CH4 OUT pins measured  GND/5V/0.34V when not connected to the servo.

    You must have a short somewhere.

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