Measuring BEC functionality with multimeter

[Joost]

So I’ve got a bit of a conundrum, last week I managed to ruin my integrated naze32. It was plugged into the pc and I wasn’t paying attention and accidentally got the usb cable stuck and tore the microUSB port almost clear of the frame.

While anoying, I figured I could fix this with some glue and a bit of fancy soldering, so I took it appart and set to work. Afterward it was working again and I managed to finish setting up Triflight 0.5 beta 2. Up untill the point I plugged in the flight battery -> My RX (X4R-SB) went up in smoke. I figured I ruined the naze as well, and so ordered new parts. However after taking it appart again I couldn’t find any damage to the board.(See picture). When taking it appart there were a few bits that were iffy where a short might have taken place.

1. vbat+ to buzzer+
2. X4R-SB (using inverter bypass hack) signal to ground

First I figured it was nr 1, and as such desoldered the vbat entirely & cleaning the holes. Since I had a old D4R lying around, plugged it in and added a battery to see if it would go up i smoke -> it didn’t. However, the naze wasn’t getting any power (no leds). In the meantime a new X4R-SB arrived and I’ve hooked it up, bound it (using flight batter), which went fine.

I was just wondering, if the naze looks intact, but isn’t getting any power, could it be the BEC that failed? So I am looking at how I could use a multimeter to check if its still working ok.

picture of the naze:
http://onebit.us/x/i/YAmaby8S6G.jpg

[RCExplorer – David]

Use a multimeter set to voltage reading and measure the 5V output from the BEC (the BEC + and – pads that you solder the little jumper cable between the two boards). It should give a stable 5V out.

Sorry to hear about the poor X4R :/

The processor on the Naze might be dead internally while looking fine on the outside.

[Joost]

Good to know, I expected that that if the naze would be fried by the vbat it would look as wrecked as the x4r with bubbly plastic melt on all the microprocessors.

About the BEC, the two(?) capacitors in front are for absorbing the spikes caused by hooking up the battery yes?

[RCExplorer – David]

The little grey one on absorbs on the input side and the yellow one is for stabilising the output voltage. It’s crucial that the yellow one is working or the regulator freaks out

[Joost]

Thanks! I’ll get to measuring when I get home, I’ll update with a post-mortem when I figured it out. 😀

[LeoTheHuman]

+vbat to +buzzer means you would have vbat on all the +5v rail. With 4S that would definitely kill most of the sensors and processors on the boards, both naze and Rx. That would be very unfortunate.

[Joost]

Replacement integrated naze32 board arrived, flashed, tested and built into the copter. Measured the BEC and it was outputting a nice steady 5V. So everything is in working order again. Ended up removing the vbat connections all together, depending entirely on FrSky FLVSS voltage sensor so my Taranis notifies me when voltage gets too low or cell difference too big.

The old naze was dead as a doorknob indeed, as was the old X4R-SB, Motors, ESCs, FLVSS and servo are intact and working as before.

Lesson: If soldering vbat(or anything really), carefully check your work afterward for any accidental connections. And when in doubt, take it apart, clean it up and try again.

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