Hello, i have another problem with my APM. I suspect i have a fried MUX, here are my symptoms :
Do you think my APM board is fried ? do i need to change the red board only ? Is there other things to test to have a more precise diagnostic ? is it possible to revive the MUX ?
The part number for the MUX is 74ACT157SC, and you can replace it directly. The chip does not need to be programmed.
Ok thanks! can't find a chip here though, all 74act157 or 74ls157 are in DIP. So far no luck in finding SOIC. I guess I have to ship it from somewhere haha. Thanks for the heads up though.
Little update on my case : I've reflashed the 328P with an AVRDragon programmer, went fine. I've reset the EEPROM of the ardupilot, and after many tests, here is the status :
I think i will have to declare my APM red card dead at some point... :/ any new ideas ?
I have also had a dead mux chip - can't remember if the symptoms were the same as yours though.
The chip can be replaced, it can be done with a soldering iron, it is easier if you use some flux though.
Alternatively, I 'fixed' mine by lifting the enable pin on the mux, that permanantly means that I cannot do rx passthrought, but I only fly a copter so it does not matter to me. Advantage is I don't have to replace the mux chip.
I discovered this only after replacing the 328 (for no reason in the end).
where you buy that chip ?
where i can buy this chip(74ACT157D) , i can't found in local store :(