Hello!

I've just received my first pre-built Eachine 6S drone and decided to test it. I don't have any batteries for now so I plugged-in output of old laptop charger 19.5V to drone input just to test SpeedyBee Bluetooth interface. There was a spark when contacted, so I thought there is some capacitor is going to be charged. After laptop charger turned off short circuit protection I've given another try but there was a spark and nothing else as well.
I've tested electric resistance of drone input and it was exactly zero. I've tested voltage and it was 0 as well! So I don't understand what is going on? It's not capacitor behavior?  What will happen when I plug-in 100C battery here? I've made no changes in drone construction, just plugged-in X8R receiver. I know how to use a multimeter for sure, and I didn't mix up the polarity of laptop -> drone contacts, trust me. So, it's a bad sign, isn't it?

Zero resistance on the power lead? That's a short circuit.
Resistance should climb to infinite as the capacitor gets fully charged.

Just to be clear, which pads exactly did you connect the 19.5V supply to? Some photos might be useful.

And exactly which two pads did you do a continuity test across?

I'm guessing it's the Wizard X220SHV that you've got (?)

Hey guys!

I've made a bunch of photos: https://drive.google.com/open?id=1PzqO3L...77i41LzbwZ Please take a look. The yellow connector doesn't change anything, it just helps me to handle wires in order to take photos. Without it all data is the same.

SnowLeopardFPV, it's X220HV.
One of my batteries just came today. It's the first time when I'm glad to the slowness of post mail! I'll start disassembling now, maybe any guesses where to look at?

Ok, that's the short circuit. I found the place, look at photos. Not sure how to exactly fix it without damaging bandwidth of connections. Re-solder both contacts?

PS. I'm sad. How could they make such a sh*t? Both contacts touches this circuit element. What if the others drones where only one contact touches the metal will get fired in air after some vibrations or when drone hit the ground?

Can you test continuity?

The red wire can touch the current shunt. The black wire should not contact the shunt. I would just resolder the black wire.

Personally I would desolder, shorten the power lead exposed wires and maybe even rotate the wires 180º.

And other than re-soldering to fix the problem, I would send the pictures to Banggood telling them about the problem and letting them know how disappointed you are with their poor quality control. At the very least I would expect some freebies or some vouchers from them by way of compensation.

(13-Mar-2019, 09:04 PM)brnmd Wrote: Can you test continuity?

I did, wires are ok.

(13-Mar-2019, 09:13 PM)voodoo614 Wrote: The red wire can touch the current shunt. The black wire should not contact the shunt. I would just resolder the black wire.

Can you please explain why is it? I want to understand the topic well. How this asymmetry comes, why positive can and not vice versa? 

(13-Mar-2019, 09:55 PM)Maiden Flight Wrote: Personally I would desolder, shorten the power lead exposed wires and maybe even rotate the wires 180º.

Hmm, this solution looks really logical. We can mitigate the loss of current on such a long way by making it ~4 times shorter. Any ideas why engineers did a long path? Risk of props to hits wires?

(13-Mar-2019, 10:25 PM)SnowLeopardFPV Wrote: And other than re-soldering to fix the problem, I would send the pictures to Banggood telling them about the problem and letting them know how disappointed you are with their poor quality control. At the very least I would expect some freebies or some vouchers from them by way of compensation.

Well, I want to. But it has been ordered from Aliexpress, not Banggood.

I meant only the exposed wire part. From the photos seems that can be shortened. Also, but this is a personal preference, I would route these wires from the side of the quad coming outwards from the board.

(13-Mar-2019, 11:21 PM)savinovalex Wrote: Can you please explain why is it? I want to understand the topic well. How this asymmetry comes, why positive can and not vice versa? 

On the 4-in-1 ESC used on the X220HV, the current comes in on the positive wire, through the shunt resistor (the rectangular copper item right next to the positive pad), and then onto the rest of the circuit (the "load"). If the black wire is touching the shunt resistor then the "load" would just get bypassed with current flowing into the positive pad, through the shunt resistor, and then back out via the negative pad. The circuit diagram below shows how a shunt resistor works within a circuit.

(13-Mar-2019, 11:21 PM)savinovalex Wrote: Well, I want to. But it has been ordered from Aliexpress, not Banggood.

If you raise a dispute you may be able to negotiate a partial refund, or some money off other products they sell. I've been successful in doing exactly that with an AliExpress purchase in the past. I guess it's up to you if you want to try that.

SnowLeopardFPV, thank you VERY much for a detailed answer! I've read about shunt and it becomes clear now. I have a little concern considering the precision of current measuring since we adding another contact in a part of the route of current. I think measure should give an error to the side of the lower current value because we figuratively expand bandwidth of the shunt. But, the point of contact is small and lies near the "start", so maybe influence is imperceptible.

I've written to EACHINE Official Store on aliexpress, so let's wait for reaction about this issue. Thank everyone!