Is my MOSFET fried

[mafu10]

Chaps,

I am not new to mosfets, i had my first mosfet about 6 years ago from trigger master and that's all I have used since.

I have recently taken the front end off my G&G m4 to fit a shorter rail system with a silencer running into it, part of the process involved cutting the signal wires of the G&G fet.

So as I see it the mosfet is wired up in my favourite way - 2 wires running to the motor and I assume the 2 signal wires running to the trigger switch (I assume because I haven't taken the box apart).

I wired it back up today having soldered the signal wires back together and the gun ran, a bit sluggish and the fet got too hot to touch after 10 or so semi auto squeezes. So I stopped checked everything was fine and plugged the battery back in, nothing worked!

So I thought to myself ok I have somehow fried the fet, it's probably a piece of crap. HOWEVER I began to cut it out and did an experiment where I touched the signal wires together on the fet side of the cut and the gun fires up in full auto!

So is the fet fried or is there a problem down on the trigger contacts? I don't want to open it up to see, this is meant to be my un-molestered standard gun I would never open up. I can't see how there could be a problem down in the trigger though because technically there should be no current of any significance down in there. Surely the fet can't be fried if it's working when the signal wires cross??

[Tom Andrews]

Re: Is my MOSFET fried

If shorting the two data /signal wires together that are between the cut and the fet allows the gun to fire, then logically it has to be the trigger unit. But not sure why you have this problem unless one of the data/ signal wires is shorting out against the gearbox body. Does semi work as well?

As it was working before you stripped the front end, it seems the only conclusion I can think of.

[mafu10]

Re: Is my MOSFET fried

Well that was my thinking, logically it has to be down the line from the mosfet where the problem lies but I see no reason why there should be a problem. The fact the mosfet was too hot to touch after only 10 or so shots made me think it had a problem in the circuit board.

When I cross the signal wires on the mosfet side of the cut I only get full auto, but this would be whatbi would expect as you need the trigger cut off mechanism to get semi, as far as I understand it - I'm not a gearbox mastermind.

I really want to avoid buying a new fet when the problem might be simples.

[mafu10]

Re: Is my MOSFET fried

Definitely fried - wired it back in, plugged in the battery and without even pulling the trigger a crackle and burning smell. I won't be trusting G&G fets ever again.