View Full Version : Keep Frying FET

2016.10.19, 11:28 AM
Been trying to fix one of our ASF board.

Long story short, FETs keep frying when applying throttle without motor connected. Tried replacing FET and same thing happen again. Looks like something shorted with the pcb? Any of you guys have similar experience?

2016.10.19, 12:02 PM
Are you absolutely sure you're soldering them in the right way around? I would think they would fry immediately on power up if you did put them in backwards though.

If you have a multi meter, with the board powered down, measure the resistance between the two motor terminals. It should be in the 100's of K ohms or low M ohms. If it's a small number, the outputs of the FETs are shorted.

Are you using an iron or hot air to swap the FETs?

2016.10.19, 12:51 PM
TeeSquared, thanks for your reply.

I followed the same orientation as where the "dot" was on the FET as before, unless the FET I used was not suitable for the board... possible?
But yes, the FET didn't fry immediately. It was only after I apply throttle to it, then it fried.. let me check the voltage as you suggested across the motor terminal tonight too..

To be honest, I only know of soldering with soldering iron. I removed the old FET with copper braid and solder iron. But I am not familiar with the "hot air" method?

2016.10.20, 11:33 AM
What is the part # of the replacement FET you are using?

2016.10.20, 05:14 PM
It is very possible the part you are soldering in is not a direct replacement. There are many thousands of FETs that come in that same 8-SOIC package. What Steve said...whats the part number of your FET replacement?

"Hot air" soldering is a popular soldering technique for assembling or reworking surface mount components. It involves using a tiny hot air gun with a very fine tip to blow super hot air at what you are soldering. There is no physical contact like there is with a traditional iron. YouTube has many nice video tutorials that show you how it's done :) I like this method for swapping FETs because I find using a traditional iron slightly clumsy though it's still very possible.

The reason I ask though is because it's easy to bridge multiple pads or component leads with an old school iron, particularly without flux. It's hard or impossible to do with hot air.

2016.10.21, 08:07 AM
Thanks for the inputs!

The original one that comes with the ASF board is 3010 4A2 60G5
and i replaced them with 3010 962 6140

I thought since they are both the "3010", they should probably be okie? Or they need to be exact?

2016.10.21, 11:25 AM
It sounds like you're using the proper part. The "3010" is the specific FET part number(well part of it anyway), the other numbers are batch and date codes.
If there were no shorts on the soldering then there is probably a short on the output. It is also possible the circuitry which controls the FET's is damaged but that is quite rare.
If you have any kind of multimeter you can measure the resistance of the two contacts on the PCB for the motor connection. As TeeSquared has already said the resistance should be quite high.

2016.10.21, 12:35 PM
are you continually popping one or more fets? the same one(s) or no?

2016.10.22, 09:41 AM
Thanks again guys! Tested the resistance across the motor terminal last night, and it was about 1Mohm, so I guess there is no short there, but I appreciate the suggestion and worth trying..

I think we will likely get some fresh set of FET for one last try...