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Old Feb 18, 2013, 03:44 AM
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United States, CA, Marin County
Joined Apr 2009
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Fire!

I reassembled my helicopter (Trex 600 ESP) last night after a trip from LA to South Korea. I took it to a field near my apartment today. I plugged in the BEC battery and everything appeared to be working correctly.

When I plugged in the flight battery, it responded with a few beeps that sounded normal to me. I flipped off the throttle hold, and eased the throttle up. The blade pitch changed as it should, but the blades didn't spin.

I unplugged everything and checked my radio. I checked the "reverse" menu and noticed that the throttle was reversed (not sure how I overlooked that). I changed throttle from "reverse" to "normal".

Everything else appeared to be correct, so I plugged the batteries in again. Same problem. The servos responded appropriately, but the motor didn't move. I moved the throttle stick a few more times, and was about to shut it down, when the motor came to life. It spun the blades one or two revolutions, and then orange smoke began to pour from the helicopter. A few seconds later, flames came up from under the helicopter, but they went away after about three seconds.

I unplugged the batteries and saw that the ESC was laying in three parts on the ground under the helicopter. The attached pictures are of the helicopter immediately after and the ESC (stock Align controller).

I checked for reverse polarization, and everything appeared to be normal. I am absolutely stumped. I have to imagine that I did something stupid to cause this, but I can't figure it out. Any ideas???
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Old Feb 18, 2013, 04:21 AM
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Australia, VIC
Joined Dec 2011
1,108 Posts
Problem is , the battery can supply a lot of power , any issue can cause a massive increase in load and the ESC can fry ...
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Old Feb 18, 2013, 05:07 AM
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Denver, CO
Joined Dec 2005
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All mine that have burned up, was after a crash in idle up, full power. Usually the unsolder themselves from the power, or just burn part of the esc. That looks fairly even across the esc, so I would test the motor, and its leads for signs of shorting.
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Old Feb 18, 2013, 08:52 AM
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United States, CA, Marin County
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I'm embarrassed to say - I'm not sure that I know how to check for a short in the motor. I didn't see any obvious shorts in the exterior connections, but I don't know how to figure out if there is an internal short.
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Old Feb 18, 2013, 09:08 AM
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United States, CT, Trumbull
Joined Dec 2007
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That's the easy part . You need a multi meter though to check it . Just chech all the leads to see resistance
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Old Feb 18, 2013, 10:05 AM
WOS
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United States, IN, Michigan City
Joined Nov 2003
808 Posts
using an ohm meter, check two leads at a time,outer and middle, opposite outer and middle, then both outers. you should see about the same reading +- 5 to 10%.
THEN! Check each wire separetly , one at a time and motor shell. one lead on a wire, other lead on the motor case. Make sure your fingers do not touch the probe on this tes as the ohm meter will read resistance from your hand. Each one to the case you should have no resistance or a very high resistance.
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Old Feb 19, 2013, 01:57 AM
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United States, CA, Marin County
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I don't want to misunderstand, because I'm a beginner and some things seem counter-intuitive... When I test the resistance between individual wires and the case, I should see zero resistance OR high resistance - correct? What constitutes high resistance (can you give me a ballpark so I know what to look for)?

Thanks for bearing with me. I appreciate the info.

-Taft
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Old Feb 19, 2013, 03:46 AM
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Ok, I found a multimeter today (wasn't easy here). I tested the continuity between the three leads (red, blue, black), the leads/case and the leads/stator. There was no resistance between each of the leads (all possible combinations, always 0 Ohms). There was infinite resistance between all other meansurements. No continuity between any of the wires and the case or stator.
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Old Feb 19, 2013, 04:53 AM
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Denver, CO
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Consumer multimeters don't have the accuracy needed to really test this small of a motor. it will just let you know if something is really wrong with it. To get a better idea you would need to do several test including turning the motor with something like a drill, to measure the output. You'll need a few things to do that properly. I'll look for a link to good instructions, not sure if I saved that. An oscilloscope would help tremendously, but if a multimeter is hard to find, an oscilloscope might be impossible to find.
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Old Feb 19, 2013, 05:59 AM
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I think it might be possible to find an oscilloscope here. Once I found the "electronics market" in my town, I found TONS of electronics. Unlike in the states, there are a million tiny niche stores instead of a big electronics superstore, but I'm sure it is somewhere here. I'm not sure how ridiculously expensive it might be.
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Old Feb 19, 2013, 06:21 PM
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What a coincidence, I just did a similar thing. I am just starting with helis, and having got a new radio and installed the rx was checking servos for reverse, and inadvertently reversed throttle channel. There was a bit of thrashing about on the floor, followed by a (very smoky) fire!
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Old Feb 19, 2013, 08:58 PM
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United States, IL, Carol Stream
Joined Nov 2009
652 Posts
is there a way to just power the motor up and check amp draw? maybe put a fuse inline somewhere to protect the esc? I know sometimes shorts may not show up til there is a little heat. Can the battery spike and cause this some how? is there any way to test the battery? did the battery puff at all?
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Old Feb 20, 2013, 04:15 AM
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Denver, CO
Joined Dec 2005
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Yes, you can use a fuse. Some more tests here
http://www.rcgroups.com/forums/showthread.php?t=873872
If you don't have a drill, turning by hand can be done. It will feel very different between windings tests if one is shorted, and the others not.
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Old Feb 21, 2013, 08:01 PM
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Southern Ohio
Joined Mar 2009
1,340 Posts
Man that sucks buddy.
I'm still scared of electric helis and lipo fires....Sticking to my nitro.

Hope you get it fixed and flying quick.
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Old Feb 23, 2013, 07:46 AM
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United States, CA, Marin County
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Thanks for your help, guys! I finally figured out what the problem was. I was right - I made a stupid mistake and didn't realize it in time. I assumed that the stock Align ESC had a BEC, so I snipped the red servo wire. Apparently I was wrong - no internal BEC. That's why it burned up on me.

I installed a new Castle Talon 90 HV ESC. I applied throttle and it spun up normall. I think I'm back in business.

Thanks again for all the ideas and support.
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