Please Help! Non-stop BEEP after PMU V2 install

[Phantom101]

Hi,
I´ve just purchased a Dji Zenmuse H3-2d, I followed every instructions precisely to install it. Use PMU v2, but when I replace the X3 channel by the PMU v2 cable as instructed, I get a BEEP...BEEP...BEEP...BEEP...BEEP.. and it doesn't stop. If I replace the PMU v2 cable by the original cable that was in X3 channel, the BEEP stops, and it powers up normally.
Could you please help me with this issue?

 

[MrMediaGuy]

Hard to speculate without being able to examine it. The X3 channel is used by the NAZA for voltage sensing (it's how it knows when your battery is getting low and signals you to land). So if it's not getting data on X3 from the PMU, I would suspect you either have a defective PMU *or* maybe the PMU is not correctly soldered to the main board. Have you checked all your solder joints? And I'm sure you checked the orientation of the plug into the X3 port on the NAZA -- dark brown wire on top?

 

[Phantom101]

You were right, I re-checked all my solder joints by pulling the wires a bit harder and one of them go loose. Re did it, and all worked fine. However, after my first test flights with the zenmuse I noticed the Phantom much more unstable when hoovering in GPS mode. I performed the compass calibration before the flight, do I need to do any further calibration for it to recover it's original stability, now with the extra weight?

 

[MrMediaGuy]

I would always do an Advanced IMU calibration in the NAZA Assistant after opening the shell and tinkering inside. There's nothing special you need to do with regard to the extra weight, but the IMU calibration should fix it. One tip -- when you're ready to run the calibration, leave your Phantom unplugged for at least 10 minutes (20 if you can wait that long), then plug in the USB first, open the NAZA Assistant, then plug in the Phantom battery. Go into the Assistant right away and run the Advanced IMU calibration. (If you wait too long, the IMU heats up too much and you'll get a message to turn it off for 10 minutes.)

Once that's done, do another compass calibration before you fly. Make sure you aren't near any metal objects (no cell phone or car keys in your pocket) and keep the transmitter a good 20 feet away once you enter calibration mode. If it's still unstable after all that, I'd recalibrate one more time. Make sure during the Advanced Calbration that you keep the Phantom perfectly level and absolutely still -- I don't even move my chair or take a step during the process.

And just a comment -- I wouldn't pull on those solder joints "a bit harder." I'd grab that wire and see if I could pick up the Phantom from the solder joint. (Maybe not literally, but you REALLY want to make sure these connections are rock solid. If something vibrates loose during flight, you will have a very unpleasant 5 seconds as you watch your Phantom drop like a rock.)

 

[Phantom101]

Very usefull information, thank you very much for your help. I'll do the Advanced IMU calibration exaclty how you described it and let you know the result. It was good you pointed out the solder joints, I'm no specialist in solder, actually it was my first time doing that, had kind of a hard time making them work, I'll re check them again and try to make it more solid. I covered them with the tape DJI suggests in their video, any tips on how to cover them in a more effective way in order to make the connection stronger?

 

[MrMediaGuy]

Honestly a "good" solder joint is crazy strong -- if you pulled hard enough, it should literally pull the copper trace off the PC board OR the wire should break before the solder joint does. (Although of course you don't want to try that!)

The enemy of soldering is what's called a "cold joint," where the wire moves too much while the solder is cooling. That causes the lattice structure of the solder to be malformed and subject to crumbling under stress or tension. The way you normally would spot this using normal 60/40 tin/lead solder is when the solder joint looks "frosty" on the surface when cooled.

Unfortunately the Phantom uses lead-free solder. This is great provided that you have a good soldering iron that gets hot enough to melt it (you probably need a 40W iron) and that there is enough existing solder to make a good joint. If you had to add solder, and you only have "leaded" solder to use, it will still work -- BUT the joint will frost over no matter whether it's good or bad. So you can't easily spot a cold joint.

The best tip I can give you is to watch the DJI video where they show soldering in the PMU-V2, or maybe even better, the video showing how to replace/install the new upgrade board -- just so you can watch how they solder on the wires. You need a good 30-40W soldering iron, ideally with a chisel tip (rather than a small point) because it's a large blob of solder. Put the new wire on top of the blob, and apply the iron to the wire, not to the solder underneath. Let the heat transfer through the wire to melt the solder. That way when the solder does finally "give," you'll know that the wire is already plenty hot enough to sink in and bond well. if your iron isn't quite hot or powerful enough, you might need to cheat a bit and touch both the solder underneath and the wire at the same time.

Insulation is purely that -- insulation from short circuits; don't try to rely on insulation to add strength to a solder joint. Properly done, it should be plenty strong on its own.