Airsoft Forums UK

lets start with what mosfet it has?

Perun v3 hybrid.

Depends on how much juice you are loading in your RIF.

What amperage and voltage cells are you using?

MOSFET are reasonably robust until you start over driving the gate.

You then push more than the mosfet can handle and the motor will likely have a fair bit of back EMF as a result.

So if the MOSFET is getting hot, its possibly the battery but equally, it can be the load that is driving the MOSFET in to overheat mode.

I use a 7.4v 1450mAh 30c in there because it's the only battery I own that fits under the dust cover.

Gun is running on 12:1 gears (short stroked by 2) and a SHS m90 spring, so it's not like there's much load on the motor (which is the stock E&L M170, basically a rebranded SHS HT motor). ROF is in the 22s with said 7.4 battery and a touch over 30 with a 11.1v one.

I have the same internals on my two M4s with different MOSFETs (one runs on a Titan, the other on a Perun v2 optical) and none of those ever showed any sign of overheating.

All I did yesterday was remove the gearbox from the body because i had other things to do, but tomorrow it's national holiday so I have plenty of time to sort it out.

Check that you are not providing a high resistance short to the chassis...

If you been inside, you could have tightened the motor housing too tight and its pushed hard against the gears and the problem is only manifesting with the higher ROF.

The back EMF off the motor may be screwing with your MOSFET board...

When it comes to electricals, there is NOS, then the old Occams Razor comes out and has to put the blame on the MOSFET itself as they do wear out.

People don't realise that electricity is abrasive at the molecular level and its how wires wear our and too much power causes heat from all that molecular friction of having to carry a higher load.

So the mosfet may be on its way out and if you have put other mosfets in and no problems, then its got to be that mosfet controller, if it behaves on a lower voltage, then its the fact you're driving the ROF too hard that is the problem.


 

grappa

Mosfet is brand new btw and I've put around idk, 400 shots through it?

My guess is that the last time I worked on it (swapped gears, short stroked and installed the new mosfet) I slightly messed up the bevel gear's shimming, so that now it's too tight against the pinion and creates enough unnecessary friction to overheat the wiring (so the mosfet goes in protection mode and shuts itself down).

This issue happened on a very warm day to say the least (it was mid summer and about 35/36°) and I haven't touched the gun since.

As I said earlier I only use 7.4s in that gun because that's all it can fit.

@ak2m4yes, loads of grappa, especially in this temperature

@AirSniper I very much doubt that something as fundamental as back emf protection is missing form the Perun MOSFETs.

I would also highly doubt that @skara has used this gun enough to "wear out" the MOSFET.

More likely that a wire has got trapped putting the gearbox back in.

MOSFETs heating up are usually down to current draw.

So either too much current or too much demand is being placed on the mosfet.

If you have swapped out the motor, try with the original in and if its all OK then its the new motor.

To find the fault you need to go through and test each part you messed with.

Process of elimination will lead to the faulty part and just because something is new... does not mean that it s in working order..!

Check the coil resistance, for all you know, you may have a malformed coil in the motor...
 

Okay.

Mosfet is fine, I've left it to run for a bit with the motor still plugged but disconnected from the gearbox and everything is cold (yeah yeah there is no load, I know) but I figured it would still heat up a little bit.

Also the shimming seems to be fine, haven't cracked the gearbox open yet but the bevel has about 0.1/0.2 millimetres of axial movement even with the motor bolted on and cranked all the way in.

I'll give it a good check anyway.

The wiring is fine, it's not pinched nor cut, when I wired the mosfet (v3 hybrids need some soldering) I considered how the box would sit inside the body and left enough slack to move the wires around a little bit while still not catching on the selector linkage nor the body.

The motor is a 16tpa 29k rpm one (SHS HT but with the E&L logo engraved on the can, comes with the gun) and it's not burned out nor damaged apart from some external scratches.

Did some testing and everything seems to be in working order.

Although now the mosfet can't read the sector gear anymore ?

I'm gonna have to tear it open again to clean the sensors because the inside of the gearbox is a bit messy, but can't be arsed now, I'll do it this Saturday.

Ok, you may have ruled out the motor and it could be the gear box, have you tried getting a engineers exploded view to verify that the box is back in its proper configuration?

I am sure if the company that makes the gear box understands your predicament, they will release a copy if none are available online.

I did this from my Weirauch HW100 rifle as I needed to strip and service it and cleaning the barrel means disassembly of parts that need drawings! 

As for my RIF, I have been banging on at G & G the importance of having these resources available for people to effect repairs on their sport equipment.

There may be a youtube video for your gearbox unit... I have solved many a problem using youtube this way.

I am waiting until mine need a really overdue service before I try cracking my pair open.

Good luck.