MOSFET problems

[T.Rokey]

Hey all,

Recently I had purchased a gate electronics merf 3.2 and had it installed for me by a tech. I had followed the instruction manual and a couple guides online to correctly program the mosfet and all seemed to go expected. Until I connected the battery so that I could shoot the gun, it starts shooting in full auto as soon as the battery is connected regardless of fire selector and without the trigger being pulled.

I did a quick online search and most results suggested it is burnt out, so I am wondering if this is correct? Or if any one has any other suggestions to what it might be.

Thanks,

T.Rokey

 

[Sitting Duck]

Short on the signal wire

Pretty sure Gates are guaranteed for a year

First off explain a bit more coz how the heck

Can a "tech" install something that badly n untested ???

Also programmable fet's normally have a 5sec window when connecting battery

In other words this is where you get the time to customise the bursts n crap...

So if fet is programmed correctly, then you WAIT

5 seconds before pulling trigger if you fitted a battery on there....

Otherwise you enter the "programming" mode

Which you may have done by accident and messed up the stored settings so that it no longer cycles a 3rnd burst

For the record I don't own a Merf 3.2

But messed around with a Kong II

Which is same meat different gravy

Only real difference is Merf is Active Breaking fet

Re-read manual and look for a "restore or default" mode

That should return the Merf back to a default state if programming messed up

However if no joy, then a process of elimination test with a basic normal 3034 fet...

Unplug the Merf with the deans connectors

The plug in a basic non AB fet with signal wire

And she should work if no shorts

If so then Merf could be boned

If still going nutz then you got a shirt on signal wire to fet

But your "tech" should ofvsorted and tested this all out tbh

Or it can tested with a multimeter for voltage or continuity

If you measure signal wire n negative battery

You should not get any voltage until you pull trigger

There are a few ways to test out stuff, could be defective but likely to be short or messed up programming

 

[T.Rokey]

Yes it does say it ha 12 months warranty.

The gun had been sent back to the shop it was purchased from due to a over clocking issue and a hop problem that was discovered to be a ripped rubber. Whilst is was in the shop I asked for the FET to be installed, and there it was installed.

Yeh the programme mode can be entered by holding the trigger whilst plugging in the battery. Also LED lights display a sequence of 4 lights in different orders/colours when you are programming mode so that you can navigate what part you are programming. None of these criteria were met when plugging the battery in which suggests that the gun is ready to fire, but as soon as the battery is connected the gun shoots in full auto even is it is on safe and the trigger is not being pulled.

Thanks for the reply and hope the added info helps explain a little more

T.Rokey

 

[Sitting Duck]

Sounds like the first to check is signal wire...

Think that is the smaller black mini deans connector

That wire that runs to turn on fet may have got chewed up by motor, crimped/clamped by gearbox closing up or even the classic M4 pin punching right through wires as it got fitted...

That is my guess atm - a short, probably signal wire

 

[T.Rokey]

Okay thanks, I will try asap to check it over and see if there are any problems that you had mentioned with the wire.

Thanks,

T.Rokey

 

[Sitting Duck]

Think the Merf's programming mode is done by unplugging deans fet to motor lead ????

Well that is what I read in Merf PDF manual or something

But deffo check for short circuit first

 

[Spatch]

Merf3.2 if installed correctly, the trigger wire goes from the fet to the trigger contacts, there is nothing in t he programming that should or realistically cause what you're describing, it sounds more like the tech has not put the trigger contact spring back in correctly so the contact is being permanently made

Duck, you're right, to program it you remove the connection that goes directly to the motor, leaving only the trigger signal wire in place and by connecting the battery

 

[Sitting Duck]

Realistically there are a number of ways to test this n that on it

suppose the easiest method if OP doesn't have test meter n stuff

pull off the mini deans signal connector

The mini deans has two connection points

a posi supply & return (signal wire) - so it should be a case of bridged those connections

then that in effect is the low amp current from trigger

pic says 1,000 words..............

that should work even if you got 1 or 2 wires going into the black mini deans connector

if it all works properly then ya tech is a nob !!!!!

he might of wired a posi lead to wrong side of the mini deans - eg: 7.4v to 7.4v supply

but that shouldn't cause it to fire I would of thought as it is same 7.4v+ supply

most likely if 2 wires coming off - eg 4+5 then these may have shorted

or wired signal single wire wrong/shorted

or trigger stuck shut as Spatch suggested

Who knows atm but quick test of Merf or let's call him Murphy

Anyway - remove black mini deans - bridge them connectors - CAREFULLY with insulated wire

(suppose to be super safe test eviroment - a small switch with 2 wires on then jam into black mini deans connection point)

c'mon - use some common sense here but you get the idea of how to run a quick test but use some 18 pence

and FFS don't try to short any larger red deans - you are just gonna test the BLACK MINI deans connection in pic

(This duck is not responsible for any deep fried colour blind mofo's and use switch+wires is safest method tbh)

ignore my ahh sod it what's the worst that can happen and start lipo bbq's inside my house

Hope Murphy feels better soon

 

[Sitting Duck]

Any updates on how Murphy is getting on ???

did she fire bridging 4+5 or did it start a lipo bbq ???