Focbox mosfet explosion

Oh I just noticed that you can actually see that the traces underneath are burned/destroyed so the one on the left is done :confused: You might be able to repair the one on the right using the working mosfets from the one on the left though.

The right is working, just to compare with the burned focbox at left ^^

This board cost me a lot, a dual sleeping lion lost during shipping, now a burned new focbox… But I want more power, I need to try vesc6… but cost to much $$$ holly shiiiiiiit

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Oh I see,

Other users iterations might be cheaper if it is a necessity for you.

Stewii vesc6 clone ? It’s recent, is it reliable ? :wink:

Did you ever resolve this. It looks like I have the same problem. Think I’m going to attempt a repair job. Anyone have a part number for the fets used?

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I am not sure anymore how this was resolved but before you order the transistors, remove the burnt one/s to see if there is no damage to the PCB. If there is your device may unfortunately be unrepairable. Just so you dont unnecessarily buy the mosfets and end up not using them

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All esk8ers need extra MOSFETs laying around dude. :wink:

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Well yeah that is true.

Btw, you should check the gate resistors so that you can order them at once so you dont need to pay shipping twice.

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I recognise this, can you please help me repair this? IMG-20180528-WA0001


Did you try flashing the firmware? I think that thats the issue :smiley: :smiley:


that´s a classical “turn it off and on again”!


Sad DirectFET syndrome


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Mine does not look quite that bad. Im hoping most of the damage is superficial. its clear that the top right fet is damaged but i think the other 5 are ok.


Is there any easy way to test them without removing them?

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You can test continuity between positive input and each phase wire, do the same with negative input.

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Just had some time to look at this in more detail. This is what the FET damage looked like under the TIM.


After cleaning up I start to get some clues as to whats happened.


Looks like the PCB has corroded and copper had been exposed on some areas. Also the edge of the FET seems to be corroded here. Maybe a short between the FET housing and copper has occurred.


Decided to remove the fet and asses the damage.


Yep, that defenatley looks done.


The board dident look great either. So I tried again to clean it up.


This actually doesn’t look too bad. It looks like the PCB has worn down to the copper in a few areas. Maybe this is caused by vibration or maybe water ingress? not 100% sure. also cant work out how to check the other FETS without removing them which i don’t really want to do if i can avoid it.

So I plan to re coat the bare copper areas again some how then replace the FET.

Also if anyone with the same problem ends up here in the future then this is the datasheet for the replacement FET: I ordered replacement pack of 4 from RS for £12.

Wish me luck :slight_smile:

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I think that what you are saying as a scenario of what happened is possible, another option/explanation would be that there was a short due to water possibly and the copper heated up before/while the fet was burning and that cause the solder mask to peel off or loosen so when you cleaned it you rubbed it off. Either way, it looks very promising! I have not had most success with covering bare copper like this with UV curable solder mask, any other air drying masks did not work for me, just peeled off during soldering.

Nice pictures BTW, is that from a microscope or?

pics just from my phone put in the eye-cup of a microscope, with much effort to keep things aligned :slight_smile:


my focbox have IRF7759 mosfet. you find in ALIEXPRES and EBAY and

in my case. Two diferent Firware. one firnware 3.3 master and ackmaniac 3.1xx slave

Is posible this a mistake???