Smoked BK9920
 

I was running a BK9920 on my new GTP2 in a car park - Temps seemed ok under 130 for motor and ESC so decided to drop in 5s...

Did a couple of short runs away and back and then brought it in for a temp check - Just as it got to about stationary in front of me - I saw the dreaed puff of smoke :gasp:

It looks like the MIC29300-5.0BU High-Current Low-Dropout Regulator is the chip that died... I would be interested to know:-

what this chip does
why it would blow
If it is replaceable or if this would cause other stuff to go (not this is way beyond my ability)

Thanks Chris

Gearing & Pics Below

Spur Tooth Count: 52
Pinion Tooth Count: 21
Total Voltage: 14.8
Motor KV: 1853
Tire Diameter (inches): 4.1
Vehicle Speed: 42.98 mph (69.05 km/h)

Spur Tooth Count: 52
Pinion Tooth Count: 21
Total Voltage: 18.5
Motor KV: 1853
Tire Diameter (inches): 4.1
Vehicle Speed: 53.73 mph (86.31 km/h)

http://i168.photobucket.com/albums/u...k/9920/026.jpg
http://i168.photobucket.com/albums/u...k/9920/028.jpg
http://i168.photobucket.com/albums/u...k/9920/029.jpg
http://i168.photobucket.com/albums/u...k/9920/033.jpg
http://i168.photobucket.com/albums/u...k/9920/030.jpg

That sucks, I have had good success with my 9920 on 5s. Maybe the gearing was a bit much for it? Same gearing + more voltage = higher amp draw...

Maybe you pulled more than 100amps thru it?

I will day that a KB458l (2300kv) on 4s lipo in my gtp will get a pair of trakpowers (seried to 4s) pretty warm. So I know it is pulling some juice. The motor does not get very warm though...

Maybe but was always targetting 50/60+ for this car...

It is part of built-in BEC. And it can be replaced quite easy.
It can be blown buy voltage spikes above 26V and just overtemp.

Chris,

Did you disabled the BEC? I usually ran my BKs on 6S and they worked ok. I had a problem with my 3695 and some of the engineers I know told me that it might have been some debris that got caught on some FETs and caused one phase to burn. Did you check for debris to see if that was to blame?

Yes the jumper was removed and running an ubec...

IIRC, removing the jumper just keeps the BEC from powering external devices (servos), but it still is functioning, and so is still subject to overvoltage problems. How about removing the chip altogether and back-feeding the external UBEC power into the ESC? Kinda like an Opto setup...

Yes please Mike indicated i should keep leave the red line into the rx - I thought it was effectively powering from the rx now i.e. opto...

Remove blown (cut leads with wire cutters) component and plug it in again, if it works you good to go.

If not send it to me I will take a look...

I cut off the burnt leads and presto it has some life left in it yet with the UBEC.

Will give it a go and report back! Thank you!