Output died on MUX

Hey guys,

Has anyone else experienced a failure in the APM mux?

I've been playing around with my APM and today I was playing with the dancing servo demo with some (really crappy somewhat dead) servos i've have scrounged from crashed planes.

Now I've noticed that the first output has stopped outputting.  For the dancing servo demo it no longer gives a PWM signal on Out0 (it did earlier today when i tried it).

I checked connectivity from the pin to the MUX, Out0 is connected (correctly) to MUX pin 4.  I checked that the input was connected to the ATmega1280, and it was outputting a signal.

I also verified that other channels on the MUX are working, only OUT0 (first channel of the mux) doesn't work correctly.

My questions are:
* Has anyone else experienced a failure similar to this with the mux?
* What could it be (other than somehow i fragged my mux chip)?
* Any advice other than hot-air it off and put a new one on?
* Is it possibly a power supply issue (not enough power)?


 (Also if i do take the chip off I'll put it on a test bed to verify that it failed)

You need to be a member of diydrones to add comments!

Join diydrones

Email me when people reply –


  • I feel your frustration. After a year of building my quad, it DIED.  No lights. (Yes I'm slow and mythological )  I was just read to fly it for the first time.   After removing everything from the AP main board I powered it on and felt around.  The MUX was getting hot.  I cut the VCC pin 16 with an razor and it came ALIVE. I'll replace it with CD74ACT157M - IC, LOGIC, QUAD 2-INPUT MUX, 16SOIC from e14 (6 for 3.03 US)

  • did replace mux or does any one have alternative solution
  • I had the same happen on channels 1-4 of my APM (not sure how or when I fried it) but when loading the "servo dance" sketch OUT4-7 control the servos properly but OUT0 makes it swing madly and 1-3 just makes them vibrate...

    Could this also be a fried MUX chip (have a few on order in case)

    I do NOT have a receiver connected at all (still being delivered) ... would this cause OUT0-3 to behave erratically - I thought perhaps the failsafe is switching to manual due to there being no signal on IN07 (Auto mode switch from rcvr) and there are no channel input connected so causing issues?

    Any help appreciated

  • I have kind of a similar issue, but it may not be the same thing - in manual mode, ch1 will not provide an output, all other channels seem fine, but all output channels appear to work correctly once I switch to stabilize or another auto mode. I'm running a simulation with X-Plane, and the radio inputs seem to work the entire time. I didn't see any bad connections on my first look, but I need to check more closely.

    I'm not clear on exactly what the mux does in manual vs. non-manual modes, so I'm not sure where the signal isn't coming through.

  • This is the part I used from Farnell

    Farnell Order Code: 1750389
    Manufacturer Part No: CD74ACT157M

  • Developer
    I fried mine too once, shorted output and now everything is ok. New APM will have better protection against +5V to signal pin. That's what burns it.. One pin too up and oops :)
  • Yep been there as well 8(
    On two different APM board , I had to change the MUX . I fried CH1 and CH3 (throttle) on one board and CH3(throttle) on second board.
    What I "suppose" fried it was to badly connect the servo plug from the ESC to the board, I might have connect the +5 to the signal connector.
    A friend of mime with magic hands manager to unsolder/solder new mux. Now everything is working again and will be extra careful with this now.
  • Hi Alex

    I had the same on ch2, sorted out the input and output till I found a replacement chip from Farnell. Easy to change with a standard small tip iron. I cut the legs of the old one to remove it from the pcb, then cleaned up the pads before fitting a new one. Not sure why it failed but working fine now.. If you have trouble getting one (the right pitch) let me now I have a few spare.

This reply was deleted.


DIY Robocars via Twitter
RT @SmallpixelCar: Wrote a program to find the light positions at @circuitlaunch. Here is the hypothesis of the light locations updating ba…
15 hours ago
DIY Robocars via Twitter
RT @SmallpixelCar: Broke my @HokuyoUsa Lidar today. Luckily the non-cone localization, based on @a1k0n LightSLAM idea, works. It will help…
DIY Robocars via Twitter
@gclue_akira CC @NVIDIAEmbedded
DIY Robocars via Twitter
RT @luxonis: OAK-D PoE Autonomous Vehicle (Courtesy of zonyl in our Discord: https://discord.gg/EPsZHkg9Nx) https://t.co/PNDewvJdrb
DIY Robocars via Twitter
RT @f1tenth: It is getting dark and rainy on the F1TENTH racetrack in the @LGSVLSimulator. Testing out the new flood lights for the racetra…
DIY Robocars via Twitter
RT @JoeSpeeds: Live Now! Alex of @IndyAChallenge winning @TU_Muenchen team talking about their racing strategy and open source @OpenRobotic…
Nov 20
DIY Robocars via Twitter
RT @DAVGtech: Live NOW! Alexander Wischnewski of Indy Autonomous Challenge winning TUM team talking racing @diyrobocars @Heavy02011 @Ottawa…
Nov 20
DIY Robocars via Twitter
Incredible training performance with Donkeycar https://www.youtube.com/watch?v=9yy7ASttw04
Nov 9
DIY Robocars via Twitter
RT @JoeSpeeds: Sat Nov 6 Virtual DonkeyCar (and other cars, too) Race. So bring any car? @diyrobocars @IndyAChallenge https://t.co/nZQTff5…
Oct 31
DIY Robocars via Twitter
RT @JoeSpeeds: @chr1sa awesomely scary to see in person as our $1M robot almost clipped the walls as it spun at 140mph. But it was also awe…
Oct 29
DIY Robocars via Twitter
RT @chr1sa: Hey, @a1k0n's amazing "localize by the ceiling lights" @diyrobocars made @hackaday! It's consistently been the fastest in our…
Oct 25
DIY Robocars via Twitter
RT @IMS: It’s only fitting that @BostonDynamics Spot is waving the green flag for today’s @IndyAChallenge! Watch LIVE 👉 https://t.co/NtKnO…
Oct 23
DIY Robocars via Twitter
RT @IndyAChallenge: Congratulations to @TU_Muenchen the winners of the historic @IndyAChallenge and $1M. The first autonomous racecar comp…
Oct 23
DIY Robocars via Twitter
RT @JoeSpeeds: 🏎@TU_Muenchen #ROS 2 @EclipseCyclone #DDS #Zenoh 137mph. Saturday 10am EDT @IndyAChallenge @Twitch http://indyautonomouschallenge.com/stream
Oct 23
DIY Robocars via Twitter
RT @DAVGtech: Another incident: https://t.co/G1pTxQug6B
Oct 23
DIY Robocars via Twitter
RT @DAVGtech: What a great way to connect why @diyrobocars community is so valuable and important! Have to start somewhere @IndyAChallenge…
Oct 23