I've fried my ESC 😥 or to be specific ( part of it )

Hello its me again and again :joy::joy::joy:

I’ve fried my MKSESC 75100’s buck converter ( I assume that :pleading_face:)

The esc 5v outputs only 2.7 volts now, it reads 2.2 ohms between 5v and gnd, and when the esc is powered on ( only power no motor is connected) it draws 870mA for a while then i hear a faint click and the current drops to 20mA for one second, then another faint click and the current go up again to 870mA, and the clicking loop goes on like every one second.

This coil gets extremely hot (I believe its the buck converter’s coil )

Now what I want is to fix that buck coverter or disable it and use external buck converter, I’m fine with both solutions

Well… If you wonder how I got myself here :joy::joy::joy:
The short sad story happened when I was trying to attach hall sensors to my motor , I may have I shorted the 5v of the esc to one of the motor phases by mistake, sure halls didn’t read in the motor calibration after this mistake, I coincidentally tested the 5v output to find out it puts only 2.7v, so I hooked a 7805 to the power supply to power halls, and the motor spinned smoothly yea cheers bravooo, then after a while i got overcurrent fault lol, and the esc got worm (the motor draws only 10 amps ) looking here and there , the coil mentioned in photo burnt my finger what the hell, this tiny coil heated up the whole esc’s aluminum case.

anyway lets fix things before anybody notices :smiling_imp::smiling_imp:


What’s the resistance on 3.3v to ground? Can you power up the unit just using 3.3v and gnd directly without any main power and connect via USB? What is the current draw then?

I’d have to look at the PCB on this one, but it probably goes battery → 12v → 5v → 3.3v. So if the 5v regulator is damaged, the 3.3v won’t work right unless it’s powered directly. But I have a feeling the STM32 is short and consuming all the power.


resistance between 3.3 and gnd is 630 ohms
I connected usb and connected 3.3 volts to 3.3 output of the esc nothing happened and 0 current drawn.
when powering the esc ON, the 3.3 volts output works just fine while on 20mA or 870mA
i donno the stm32 is shorted or not but motor was spinning just fine even after this short at 5v , and if its shorted it would heat up and this isnt happening its cooler than my fridge lol ,but i have a suspect

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Here is some tested continuity that reads 0 ohms

Here is this tiny component (I actually donno what is it but it looks like a diode as it has a line on one end) this component is connected from right side to gnd, and left side to 5v output, its resistance is 2 ohms ±0.2 may ne dirt or oxides on terminals , the problem here is that it reads 2 ohm on both directions ( if measuring ohmmeter leads arrangement (+ -) or (- +)
It has (FE) text on it and it gets hot ( how i knew)

I wanted to check which component gives the clicking sound , so i used a statoscope without its drum tip, and when its tube touched the (FE) it melted and smocked , leaving some residue on it

If u want me to measure any component or do any experment feel free to ask

Oh and the diode i drew on the right side is on the power board no way to see it on camera ( its complicated to show) but its large one almost the same size as the 680 buck coil

If you are lazy to read or slow reader like me​:joy::joy::joy:, I can attach a voice record or video to make it easier and faster for you

Not great, not terrible

Might be a 7.5v Zener diode in a SOD-323 package

Usually those are tested with the DMM in diode mode, should have some voltage in one direction and none in the other, but a 2 ohm resistance both ways and the heat is a pretty good indication that it should be replaced.


Here I’ve replaced that zener but as I expected , i didn’t find the same old one , I used BZX79C , couldnt even find smd one :joy::joy: , thats good cuz it will be impossible to solder

Now when I calibrate the motor it pop overcurrent fault after spinning the first half of the calibration, it draws max one ampere during the calibration

So motor detection runs in open loop, once it has it’s parameters it runs in closed loop using the voltage readings from the motor (or hall sensors at low speeds).

Do you have a production off the shelf BLDC motor you could try with it? Even a small, cheap outrunner from a drone should work.

You could try turning on real time data, click the heartbeat and enter this into the console:

foc_openloop 5 1000

That will run it in open loop (doesn’t need correct motor parameters) at 5A and 1,000 eRPMs. You can play with the eRPMs as needed. You can use an AC clamp meter to see if all 3 phases have the same current while the motor is spinning. Then try to increase the current to something like 20A. ABS MAX should be set somewhere around 150-200A for this controller. You can turn “slow abs” to true to test with, but I wouldn’t run it that way long term.

I guess the point here is to see if you can get it to run smoothly in openloop. That will tell you if at least most of the power stage is working correctly. Then you can focus on motor detection parameters and try to get that correct. Since this is a custom motor I imagine there will need to be some tweaking to get it to run right.

What’s the power source? Battery or power supply? Need roughly 30v 5A for a decent motor detection in my experience


Now the seller told me to pick larger motor from the calibration list in vesc, I did that and it detected the motor with no overcurrent fault , Here i tried that command and it worked awesome and silent

Some screeches cuz if bad bearings but the coil is almost completely silent but…

When i use the adc and hall sensors the coil is a bit loud , it shounds shhhhhhhhh :joy::joy:
I will search in Vedder’s channel and google, for solution to reduce this annoying sound, but until then can you point me to the right direction to save me some searching time :pleading_face::pleading_face:

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SMD diodes, resistors, and ceramic capacitors are all actually very easy to solder to PCBs. Just might need a magnification + light arm on a 3rd hand. You can’t accidentally short the two ends together easily which is why they’re easy to work with.

Not very helpful anymore since you have already gotten it working though :sweat_smile:

actually I’m not gonna buy 3rd arm and mag to solder smd parts, even if there are 20 parts need to be soldered, I will send them 2 streets behind mine at phone repair shop, and pay for soldering smd parts :joy: :joy: :joy: :joy:

and I love my new large Zener it looks like shrimp isn’t it :fried_shrimp: :fried_shrimp: :fried_shrimp:

Fair enough. but if you don’t already have a 3rd hand tool then how the heck have you been doing any good soldering? :thinking: Even the cheap plastic versions on amazon are well worth the cost. They do get annoying with time since the joints in the arms loosen with time so they don’t stay in the exact position you want as easily, but good metal ones with plenty of arms are pricey.

I just wouldn’t trust a random repair shop with small part soldering unless I’ve seen their work before since there are so many shops near me where they can only replace “plug and play” type parts on phones. They don’t ever do any actual pcb repairs and will just tell you that you have to buy an entire new part. Although, I do know that good repair shops do exist where they could easily fix that without any issues.

His solder job looks pretty good.

I wouldn’t have used a 3rd hand to do that either, SMD or through-hole diode. Just tweezers, a soldering iron and some flux. Clean the pads with a solder wick, tin just one pad, add some flux, grab the SMD diode with tweezers, place it while heating the tinned side, remove the iron, wait for it to harden, then solder the other side with fresh solder in one hand and the soldering iron in the other and hope you remembered to put it in the correct orientation :joy:

I meant in general not on the pcb in question. My bad for not making that clear. I only ever use mine on pcbs to hold them up closer to my face for just an easier time soldering and looking at it. Plus using the light + magnifying glass to make things easier to see.

Bent stabby tweezers are the best IMO for this. You can do it with straight stabby tweezers but the bent angle just makes life easier in my experience.

Come on guys forget about soldering school for now ,and focus on my motor sound i asked about :joy::joy::joy::joy::joy::joy:

Well , if im gonna solder smd parts i would not use 3rd arm, I would buy solder paste , clean the pcb where the action will happen, squees some past , adding part in place using tweezers, then heat it using fine tip soldering iron or hot air if available (mostly I would use the iron as I dont have hot air​:disappointed_relieved:) sounds easy and convenient huh :stuck_out_tongue::stuck_out_tongue::stuck_out_tongue:

Who wants 3rd arm lol

Imagine what I can solder if I were Goro

I would but the videos uploaded in a way that makes it unable to play. The soldering video works fine though.

That method only really works for thin wires like that where they can heat up enough for a good solder joint before it can burn you. Doesn’t work with bigger stuff like 12 awg or even just 14awg wire since it can and will burn your through the insulation.

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