RoboCat - Burning through ESCs


Building Fool-Flying Noob
This is my first Quad Build and I am about 9 mo. into the hobby as a whole. So, maybe this should be in the newbie section.

However, I have learned an amazing amount in the last 9 months. enough where I thought... "The RoboCat is a great first quad build." It's tried, Inexpensive and deemed as a decent first quad. The one I grabbed had this PDB which is the Arris Q3121. A SPRacingF3 FC. Ready to Sky 2204 2300kv motors with EMax 12A ESCs with BL Heli. they also have a 5 bladed 5030 propeller blades.


I'm have had a total of 3 ESC burn up and catch fire so far. first one, which I replaced and this last attempt, 2 more. I will happily blame my soldering skills. I am unwilling to waste any more ESCs. as I could have a number of ready to go planes that WILL work instead.

I am now filling out the forms for PSYBorg's "Fly Angry" Club. Help me see reason to tear up the form.

My question is HOW do I dismantle this in the right way to rebuild this without destroying it, and have success (please). Should I reorder the PDB?

I will upload photos tonight as I dismantle the frame to pull out the burnt out ESCs.


Faster than a speeding face plant!
Emax 12A ESCs? Gotta link or photo? IMO these should be on the short list to replace.
EDIT: I see your link. WOW, I tossed these out in 2015. Replace these ESCs. Note the reviews where 2 out of 10 reviews mentioned burning out the ESCs. Lose these and fast...

12A ESCs and 5" props on 3S is OK but not much punch. Why not consider a 4S build? You will need better ESCs. Consider the Aikons with BlHeli S for performance. You may want to drop down to 3 blades with those motors if they get too hot with the 5 blades.

If you think your soldering is to blame for ESC burnouts, use a smoke stopper. Every time I touch anything with my soldering iron I power up through this gizmo the first time. It has saved me several times over the past two years. If the light lights, yank the lipo and go find the short. Anything so you don't have to smell burnt SunnySky 2204 for a week in your shop. :black_eyed:

When you solder ESCs, use a hot iron and move fast. I use the chisel tip for ESCs and the fine tip for flight controllers. Tin pads and leads with your own solder prior to the actual join. If you have to remove old solder do so. Let it cool. Then tin with your own solder. Don't mix solders. Be sure your motor leads are well tinned and don't have any enamel on them or you can have jitters and smokes. Clean any residual flux off the ESC prior to connecting to a lipo.

I live in lightning central. I wear a wrist strap when I handle ESCs.

Always connect BOTH signal AND ground from the ESC signal pads to the flight controller.
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Wake up! Time to fly!
12 amp esc's on 3 s is Ok for two or three blades. The drag from those five bladed prop would surly smoke them specially since they are semi bull nosed.

As cheap as decent esc's are today there is no reason to be putting 12 am esc's on anything but micro sized quads. They MAY fly but come on guys.. these are quads and you KNOW we can't fly gently... Which by the way is the reason for my "Fly Angry" hehe and has nothing to do with actually being angry.

As for soldering high heat is not the answer in most cases. Proper soldering technique can get you a lot further with better results. We aint soldering plumbing here and these ain't your grandfathers soldering tools. I guess I will go thru and do the write up and possibly a video on how to properly solder without burning your gear up and still get you a reliable connection every time.

For now Foamy start by using normal temps on your iron. Clean and tin your tip EVERY time you touch it to wire, a pad or try to put two things together. Tin the esc / FC or what ever pads you are using. You are only heating the copper pad and melting solder so no high heat is necessary. Then strip and twist your wire ends you wish to solder. Clean your iron tip and tin the wire by placing the tinned iron on the wire and slowly feeding the solder between the wire and the iron. As the solder melts drag it around the wire to let the heat pull it thru the strands. when that is done clean and tin your iron, rest the tinned wire on the pad, then lightly set the iron on the tinned wire. When the solder on the wire melts keep an eye for the pad solder to melt and watch the wire sink into it. Once that happens remove the iron and most importantly DO NOT move or blow on the joint as you will instantly create a cold joint with either poor connection or very high resistance to current flow.

Practice that on something broken a few times so you can actually see what I describe. Once you do that you will never burn a trace nor over heat a board nor have a cold joint again.


Building Fool-Flying Noob
Thank you. It's like I learned so much about soldering, but I still have much to learn. (...young padawan) I have a new guy here at work that knows how to solder, so I'll have him show me what I'm messing up at lunch. and I'll make the smoke stopper.

Weird part is I haven't gotten this in the air, the caught fire trying to spool them up. The craft hadn't even tried lifting off so couldn't have been pulling enough amps. (yet)

Either way 20a ESCs are on their way (should be here by Friday) and I hope to get to this on Sunday, by then I'll have a safety device, and better knowledge. I'll keep you up to date

-Foamy DM


Faster than a speeding face plant!
Do those ESCs have a heat sink?

If so, the flat side with the heat sink should face up so the prop wash can pull more heat away from the ESC. You may burn up more ESCs having the FETs facing down on the boom than up into the cooling air. :)


Building Fool-Flying Noob
Not sure I'll look. The 20A-ers came in and I soldered them all up. (before building the smoke stopper):black_eyed: When wiring them into
the PDB again, I just mirrored the polarity on the other side. It was right so the other should be the same way, right? nope. They are reversed from side to side. So I hooked up have the PDB ESC connections backwards. And rather that confirm the wire colors and polarities, I just hooked the battery in.

What I learned:
Reversing polarity burns a hole RIGHT through the board and causes half the board to not work.
Two of the motors are SET!


Building Fool-Flying Noob
The replacement PDB came in last night from getfpv (thank you).

I had the smoke stopper built from the Gremlin build and soldered everything together. Sadly I found out the smoke stopper worked amazing. However that means I have a short. I went back and reheated and re-soldered the ESC and motor connections. I left the factory work alone. Motors 2 and 4 still make this god awful grinding noise from the quick start and stops (I think). I flashed all the ESC through BL-Heli with new firmware (same ones I did on the gremlin.

Just don't know. Maybe you can help. I really want to get this build flying. I will re-attempt this tonight. also
I have all the LEDs hooked into the 12A BEC. I have the to Eachine Assassin headlamps on and 1 of 4 pinned RGB LED strip coming on.

Does that connection suck too?

Advice, Thoughts... all is welcome.