What might have caused to fry the FlightCtrl?

ovdt

Member
Hey guys,


I'm in the process of building a Quad MK system.

The system was working fine previously, the BL Ctrl was ARF (Almost Ready to Fly) kit.

I'm using Spektrum DX8 with Quadro system. To get telemetry, I soldered +5V power pad for gettting power for telemetry module. And I changed the 16V 330uf capacitor with 25V 330uf capacitor.

The weird thing is, I did a smoke test with a success and, I powered the system with Lipo. Level calibrated and compass calibrated withh success too.
I powered the motors for 1 minute and then pufffffff.

Bl Ctrl's are healthy, but FlightCtrl seems to be dead. There's no sign of life.

What might have caused this blow out? Can it be the 25V capacitor? I'm sure that there's no short circuit. And, what should I change on the FlightCtrl to make it work again? There's no visible damage on the FlightCtrl.

View attachment 1124View attachment 1125
 

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Crash

Defies Psychics
EDIT: Use a regulated power supply or 9V battery for testing.

It sounds like a short blew out something but there could be other causes.

Check the entire board with strong magnification for solder blobs or foreign matter.

Check that the cap on the bottom of the board is not touching the board.

Connect the MKUSB to the FC and install the MKUSB jumper. Do the FC LEDs light?

Remove MKUSB...
Next to the three holes for the switch is a cylindrical diode (4007). Check for batt voltage on both sides of it.

Finally check the two voltage regulators. I don't recall which one powers the microcontroller so check both. There should be batt voltage on one pin , ground on another and 5v on the 3rd.
 
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ovdt

Member
Hello Crash,

I did the tests. No light when connected through MK-USB. No sign of life.

I connected the regulated power supply (9V) and tried checked the voltage over the 4007 diode or recoms, I can't read anything from the multimeter. Since they're at mV values.

I checked several times over and over, can't see anything abnormal on the board.

I think some component is blowed which prevent the power to get in to the board.
 

ovdt

Member
One more detail,

Please see the attached video:

I took the picture where I supposed to solder the capacitor. (originally 330uf, 16V). there's no soldering pad left on the positive (+) side.

View attachment 1130

Could that be the reason why I can't read any voltage from recoms or the diodes?

I really don't know how to fix that soldering pad.
 

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Crash

Defies Psychics
Hello Crash,

I did the tests. No light when connected through MK-USB. No sign of life.

I connected the regulated power supply (9V) and tried checked the voltage over the 4007 diode or recoms, I can't read anything from the multimeter. Since they're at mV values.

I checked several times over and over, can't see anything abnormal on the board.

I think some component is blowed which prevent the power to get in to the board.

The LEDs are switched by the Atmel chip.
Assuming you had the MKUSB connected properly, no LEDs would be a strong indication that the Atmel isn't running.

Just to make double sure, power the board with the MKUSB and you should have 5V on the 5V pad on the bottom of the board.

Power from both the USB and Batt goes through the L1 inductor before powering the microcontroller. You can check that there is 5V on both sides of it. With the board arrow up, L1 will be on the upper right side next to IC4 pads.
 

ovdt

Member
It's so weird, when I connect to MKUSB or regulated power supply, the voltage on these +5V pads are around 0.5V or even less. L1 inductor is the same also.

I'm considering to send the board for repair to Germany.

When I power FlightCtrl from PDB, I can read 9V on the molex pins. But I can't read any other voltage from the pads, recoms, diodes etc.

I cross checked the board with another healthy FlightCtrl board. Nothing seems abnormal, except the missing soldering pad on the capacitors + side.
 

Crash

Defies Psychics
Do you have a current limiting power supply that you can dial down to 5V and low mA?

It seems like something is shorting the voltage lines to ground.

Maybe before sending it off, desolder all the wires on the board just to be certain.

If you have 5V on pin 2 of the ribbon cable when the MKUSB is powered and jumper installed, but you do not have 5V on the pad on the bottom of the board when MKUSB is plugged into the FC then something has to be dragging down the voltage. That may show as a hot component if you feel around. (Look on the bottom of the board and you can see a nice wide trace between pin 2 of the 10 pin header, the 5V pad, and the recom pad.)

The cap pad in your photo probably won't matter. That leg is connected to an internal board layer. Either way, it shouldn't stop the board from running off of USB power.

The last thing that I can think of is to compare the polarized caps on your board to a photo of another board. Right next to the arrow on the FC is a polarized cap for reference. The polarity line on the caps should match another board.

If you update your post at mk.us with the other tests you have done, maybe Vpatron will have an idea.

EDIT: Can you take a picture of your setup when you are trying to power via USB.
 
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ovdt

Member
Thank you Crash,

One other detail that I didn't noticed before:

When I connect MKUSB, the USB port on the computer gets short and my mouse keyboard won't work. When I unplug the FlightCtrl form the MKUSB, keyboard and mouse starts to work, as well as the other USB hardware.

* I desoldered all wires and rechecked again everything. Nothing new.
* When I connect the USB ribbon cable, on the FlightCtrl end I have 5V on pin 2. But I don't have any 5V on other 5V pads.

Actually, MKUSB is working flawlessy. I updated my boards including this faulty one two days ago with the new firmware.

I'm checking if there's a short circuit. When I checked the big + and - pads on the bottom side, they are shorted somehow?:

View attachment 1132
(I marked the area red where I checked for short)

I compared the board picture with another one and nothing seems abnormal. This FlightCtrl was working a few weeks back and I flew about 10 hours with it. The only change I did was to change cap with 25V 330uf (which was 16V 330uf originally). And I soldered Spektrum TM1000's 5V and ground lines to the FlightCtrl.

Here is the picture of MKUSB connection:

View attachment 1131

(PS: My DC Power supply can provide me only Constant Voltage or Constant Current)
 

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Crash

Defies Psychics
So it seems that something is dragging down the 5V line. I don't know if you could have damaged recom IC4 or if that could even be the issue. I don't know what else it could be other that foreign matter on the board or an internal short on the atmel chip.

I think you are going to end up sending this board back. I would not recommend you try to pull the recom due to the possibility of board damage. It's very easy with the proper tools but judging from the cap pad, I'm guessing you don't have a good solder sucker or chipquik.
 

ovdt

Member
Thank you Crash, I got the RMA number today and I'm posting it soon. You helped a lot and I learned a lot from you, thanks again.
 


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