Fried Panda II troubleshooting

NETMF & Gadgeteer
1

I was going to do some work with my Panda II board to begin developing an altitude heading reference system. I connected the USB cable and connected an 8.4V battery to the power input. I checked the battery to make sure the advertised voltage was correct. It showed 8.57V, 0.1mA. I connected the 3V3 port to a breadboard + rail and made a continuous circuit back through to the GND port. The two components circle in yellow got very hot (smoke). I disconnected the board from the external power and the on board red LED came on for a second and I disconnected the board from USB. I let everything cool and now when I connect the panda to USB only, it is not recognized, no on board LED, nothing. I’m assuming that it is ruined. Where did I go wrong? Would I have been okay if I had had some sort of device in the circuit where I have the yellow arrow drawn? I don’t want to make this mistake again obviously. But I thought everything I’ve done here should not have caused this problem. Is is possible to replace the indicated components that got hot and salvage the board at least for development?

Thanks,
Will

2

You can’t do that. You shorted it. You need a load for you circuit.

3

Any way to salvage it?

4

looks like you shorted the3.3V regulator.

Check to see if it unsoldered itself from the board. It might need to be replaced.

5

If smoke was coming from diode I will check/replace it first.

6

disconnect power, connect USB cable, do you see anything in device manager, like a faulty device?

Does anything get hot?

Do you own a volt meter?

7

No device appears in the device manager. It does not mount. Nothing gets hot. I do have a multimeter.

8

You would have also shorted the USB jack which has overload protection so you probably have to restart the computer before it detects anything plugged in that jack.

The way you describe it makes it seem like the 5V regulator through the power jack went into shutdown then started to sink through the USB. Then when you pull the power jack it takes a surge from USB for a second until the USB jack shuts down.

Unplug everything then just plug in through the power jack. If it comes on and has 3.3V output then it might be as minor as that diode. Then you test the diode by seeing if it has voltage between ground and 1 side of it but not the other.

9

keep panda plugged in, connect one side of meter to ground pin on header (GND) and with other multimeter wire measure the voltage on both sides of the diodes D2, D3 and D4.

Also, measure the voltage on pins 5V and 3,3V and VIN.

10

D2: 4.77V / 2.4mV
D3: -173mV / -172mV
D4: 4.77V / 5.06V

5V: 4.78V
3.3V: 0.872V
VIN: -181.7mV

11

Sounds like IC4 (3.3V regulator) needs to be changed.

12

Thanks for your help. Would this be a compatible replacement?

13

Yes it should.

Of course I am personally helping you out as this is beyond GHI’s warranty and support.

14

Yes, I understand. Thanks for the support. At this point the board is lost so I can’t make it any worse. I’m going to order another one for use in the quadcopter, but hate for this one to be a total loss if I can salvage it at least for a development board to program/test with or make a rolling robot for the kids.

Thanks again,
Will

15

I believe changing the 3.3V regulator will fix it but let us know

16

One last question - is there a way to simply bypass this regulator just to get the thing working so that I can use it to debug code?

17

No?

18

You will need external 3.3V.That what that regulator supplies to the device.

19

Okay, thanks. Probably a silly question, but I’m a programmer and only just starting out with the hardware, which is why I’m in this mess.

20

I was able to get it to mount as a device and deploy code to it by supplying 3v (two AAA batteries) through the 3v3 pin at the top of the header. That’ll do!