Removing a MOSFET

[iharuyuki]

Bought a used gun and figured that th mosfet is fried. I only plan to run a 7.4v lipo or 9.6v nimh from now on so I'd like the remove the mosfet. There is a thin wire going from the MOSFET into the gun, is it safe to cut? Thank you so much for your help.

http://imgur.com/a/B0q4x

[cetane]

You're better off replacing the MOSFET if you're not comfortable opening the gun up and rewiring it. Being you can see the fet, you can replace it with pretty much any fet just splice the wires into what ever is on the new fet

[EOD Steve]

You will most likely have to separate the power leads at the trigger switch and remove the trigger wire (the thin wire you're removing).

If you're thinking of simply snipping the wire, this would not work.

[ccyg8774]

http://www.gatee.eu/images/gate/inst...picossr-en.pdf
scroll down to see the figures and see if your MOSFET is wired the same way.

[iharuyuki]

Originally Posted by ccyg8774

http://www.gatee.eu/images/gate/inst...picossr-en.pdf
scroll down to see the figures and see if your MOSFET is wired the same way.

Yes, it is wired like the figure. Though my mosfet might be across the positive terminal I'm not sure.

To the first two posters:
I'm not very comfortable with opening my gun but is the job easy to un-MOSFET my gun?




Thank you guys.

Took two photos of the mosfet:
http://imgur.com/a/B0q4x

[lurkingknight]

if you are not comfortable opening the gun, pay someone to do it because if you open it and mess it up, you're probably going to have to end up paying someone else to fix it, and it will cost you more.

You will need to take the gearbox apart, unsolder the wires from the contacts, run new wire from battery to other terminal that the thin wire is coming from and then put it all back together without fucking up something else.

[alchemy]

honestly if you don't know how to solder well, and don't understand what a mosfet is you're going to have a hard time. First of all you're going to make a mess de-soldering it, especially if its one of those fancy pre-packaged ones with lots of surface mount components around it. Second, its not a drop in replacement, meaning you can't just stick in there whatever you have lying around and hope it works (how much current is is rated for? Is it a P channel or N channel? how much voltage is required to open the gate, etc...) You can replace it with one that has similar specs and the same body shape, but you may not be able to tell just from looking at it if its broken.

[iharuyuki]

I'm not too worried about working with the MOSFET. It's the opening up the gear box to get to the trigger that would be the most trouble I think.

Thank you for all the information though.

[SawBone]

If the gearbox is a V3, I think you could get to the trigger contacts without opening the gearbox, but I'm bot 100% sure on this. It would probably be a pain to solder on them in a fully assembled state however.

[lurkingknight]

if you suck with soldering or have a shitty iron, the contacts should be removed from the contact housing, I've seen inept attempts at soldering that have melted the housing, either melting the tabs out of place so the gun doesn't work or melting the housing so the plates move so much that they touch at rest.

[cetane]

Best bet imho is just to replace the fet, and make sure everything is wired correctly (polarity & direction). If nothing is wrong with the internal wiring, it will be your easiest, least hassle and maybe even cheapest solution.

http://www.airsoftstore.ca/index.php...roducts_id=523

[iharuyuki]

Thanks for all the help everyone.

Originally Posted by cetane

Best bet imho is just to replace the fet, and make sure everything is wired correctly (polarity & direction). If nothing is wrong with the internal wiring, it will be your easiest, least hassle and maybe even cheapest solution.

http://www.airsoftstore.ca/index.php...roducts_id=523

I think that is a good idea, thanks.

Does anyone know the chances that something internal to the gun might have a problem? It would be pretty sad if I replace the mosfet but the gun still doesn't work.

[cetane]

Test it prior to MOSFET install. Put power direct to positive & negitive and see if gun cycles full auto without issues.

[ccyg8774]

Originally Posted by iharuyuki

Does anyone know the chances that something internal to the gun might have a problem? It would be pretty sad if I replace the mosfet but the gun still doesn't work.

If you have a multimeter:
Ensure your battery has charge. Remove the motor, set multimeter to voltage and measuring between the two motor leads. Ensure nothing being shorten. Connect the battery.
You may see a moment of some voltage when you initially connected the battery, then the multimeter should read to close to 0 volt.

Then pull the trigger.
On a normal working gun you should see the voltage reading almost the same as your battery voltage. If not then you have a problem in the electrical/wiring part, in your case, maybe the MOSFET.

If the voltage is normal but the gun do not cycle, check the gears and mechanical parts.

[ccyg8774]

Originally Posted by iharuyuki

Took two photos of the mosfet:
http://imgur.com/a/B0q4x

The way the blue thin wire being stripped looks scary. Did you stripped that just for the picture or it was like this before? The exposed core could touch other metal points on the MOSFET and creates problems.