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Sep 14, 2020, 03:53 PM
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Quad takes off on its own

All right, I've finally got my Shendrones Ichabod running -- again-- and now it has a problem it didn't before. Props are on. Arm it, no throttle, and it will sit there for a few seconds quietly before I hear the motors start to spin up more and more and then it'll pop up into the air and drop back down and repeatedly hop across the yard. Tried in acro, level, and horizon, similar behavior. Once it gets going there's no stopping it other than disarming it. I can fly it, just it's very hard to control.

This didn't happen when it had a Fortini F4 in it (now a Lux F7, so I could add GPS). Then it flew normally. I've had it apart twice since then.

I reset to default MATEKF722SE settings and it behaves exactly the same. Latest Betaflight, flashed this morning.

Last edited by fitek; Sep 14, 2020 at 05:54 PM.
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Sep 15, 2020, 06:49 AM
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Some of those Lux F7 have quality problems and capacitors come lose.
Send it back and get a better FC or reflow these capacitors.
Last edited by gorro; Sep 15, 2020 at 06:55 AM.
Sep 15, 2020, 11:56 AM
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If you have recommendations on better FCs I'm all ears. This is my 5th or 6th FC. All of the previous ones had some issue (the Fortini F4 worked though it was short a UART when using Crossfire). I think I've spent as much on FCs as the rest of the entire build.

I'm going to return to the F4 if I don't get this sorted out this weekend. I can live without the GPS.

Fun times, last night I tried it out again to characterize the behavior better. It slammed into the ground pretty hard and next time it popped up the battery negative cable broke off and shorted. Quad dropped out of the air shooting sparks from the lipo shorting itself. Got it on video too. Luckily it was a cheapo HobbyKing battery and it didnt take any of the rest of the rig with it (I powered it up with my bench supply).
Sep 15, 2020, 08:03 PM
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I reflowed the solder on those caps. Then I went back and tested it more.

If I power it up and don't touch the throttle, it'll mostly just sit there... I can hear the motors spin up a little occasionally. On 4s, I can actually fly reasonably well. It will randomly surge all the motors and then the power will drop out-- I can give it a bunch of throttle and it still descends. On 6s, the surging and drop out is so frequent and intense I can't safely keep it in the air more than about five seconds. (EDIT I dont know if this is because my remaining 6s battery is actually brand name and more powerful, or because of the weight distribution, which is somewhat to the rear because I'm not risking a gopro on this thing just yet).

Another crummy battery bit the dust too-- Turnigy Nanotech 4s 1300mah. I ripped it off the quad before it cooked itself on the sidewalk. At least this troubleshooting is exciting.

EDIT: Unfortunately this last lipo incident appears to have fried one of the ESCs in the 4 in 1, I'm guessing when the quad suddenly descended and the #1 motor stalled when it hit the ground. This thing is cursed. At this point I'm just looking at getting a stack, but I think I'm going to take a break from sinking money into this build.
Last edited by fitek; Sep 18, 2020 at 04:03 PM.
Oct 28, 2020, 02:26 PM
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It was indeed the Lux F7 that caused the surging issues. I swapped to a iFlight Succex-D stack and the quad flies great again.

Stupid thing cost me not just the price of the F7, but killed an ESC and a battery!

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