Kriss Vector - Adding a second MOSFET

GO HERE: TECH: Using a second MOSFET to protect your fire modes

i guess the first question is why? why add a second MOSFET in the Kriss when its already got one that supports multiple fire modes…

easy, to make sure that nice fire mode MOSFET doesn’t fry itself…the second fet handles the switching for the motor leaving the stock MOSFET unstressed

how to do this is a question that often didn’t get allot of detail. probably because its actually super simple (for those of us that understand these things i suppose)

now, your images may differ from mine. it depends on what MOSFETs you have / use but the wiring is still the same.

COMING SOON…better instructions suitable for multiple boards

the soldering on this is so bad that i will have to do it again…friggin gale blowing through the house

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so this guide here is to basically stop the vector mosfet from frying itself

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It’s a common grump and good to do before you crank up the torque if you want to keep your nice fire modes

yep ill keep that in check when i get a vector

Silly question time. Have you @zeHamish put your vector back together and tested this?
I’ve visited 3 different blaster stores recently and asked about this method and all did not know if this was possible. One even said not possible.
I want to do this to my Vector, I’m not real handy with electronics or a soldering iron. Would you be able to draw a wiring diagram, the instructions are a little confusing for me.
Or could anyone recommend me someone willing to do this for me around the Ipswich area.

it’ll work - unless you do it wrong hahahaaa

so here’s how it works which is probably more useful to you than me saying…yay, mine does. a couple others here have done similar things to their vectors as well…or so i read somewhere along the way…

fire selector…there’s some circuitry involved but what’s important is that it switches the motor on and off. that microswitch on the side of the box is super important in the process.

a fet is really just a fancy relay - in concept…so a switch where current flows on the other side

the motor lead when switched on (trigger in, fire mode X, pew pew) is the NEGATIVE.

this is testable as the positive motor wire is connected directly to the battery - use a multimeter & continuity test to confirm,

so you pull trigger, -ve wire becomes alive and all we’re doing with the second fet is using that live trigger wire (bad name but good illustration) to tell the secondary fet to fire, or otherwise…turn the motor on.

if you were to wire the secondary fet (t238 like mine or easyFet) you’d note that what you’re doing is using the trigger to switch the fet input / signal to turn the motor on.

what we’re doing with the two fet system is using the stock fet to count the cycles (pew pew pew) and instead of using the stock fet to feed the motor its amps, we’re using it to tell the secondary fet to turn the motor on and suck as many amps as it likes.

its not a silly question and its been a yarn i’ve had with many people who once they twig go…ohhh…yea, thats really quite simple :slight_smile:

but it does sound like some sort of swamp magic up until that point

my kriss isn’t entirely back together yet (awaiting some goodies) but its been tested.

easy as test regime
without the second fet

  1. pull trigger, hold in
  2. test that negative motor wire has continuity to negative battery terminal
  3. woot, we have the right wire

add in the second fet using the wire above as the trigger (it is important that your fet triggers on -ve)

  1. again, pull trigger, hold in.
  2. same test but this time the negative motor wire from the second fet to the motor gets checked for continuity

by testing without the motor attached there is no current drawn so you can’t force the magic smoke out.

see calcifer for a bottle of smoke if you do…

yay / nay? clear as mud? onboard with swamp magic?


Thanks the the detailed reply. I have not even opened my vector yet. I plan on installing a spring, o ring and metal barrel tomorrow. So while it’s opened I will look at stock fet and wiring and make a decision if it’s something I could do. Where have you placed the second fet?

the second fet will fit behind the trigger assy

i have mine in the ejection port - my battery is front mounted

if you’ve never taken it apart before watch a tear down. off to youTyube wth you :slight_smile:

be very careful when pulling the orange selectors off…there is a tiny little spring and nylon detent that is near on impossible to find if you drop it

also…don’t over tighten the smaller gearbox side screws. the acrylic is really easy to strip

oh…and there are 2 lengths too…so…make sure you get that right.

Great advise again. Thanks. Ive taken my gen8 and gen9 apart plenty of times, I’ve heard the vector is a bit more complex. Wish me luck haha.

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Well, I opened up my vector and did the spring, O ring and metal barrel. Successfully fired it after putting it back together. So happy about that. Also next time should be a breeze as I know what I’m doing.

I had a look at the mosfet while in there. If I was to add a second mosfet, think it would take me a while and be a little crude, but will give it a crack.

Took some pics of the mosfet. Which version do I have?

there’s a thread on here somewhere about the green board

i’ve not had one of those yet but the 3 wire has had some chatter about it,

Ok. Just read that thread. Couldn’t work out if it was a better board or not. I spoke with a guy at a blaster store who reckons there’s a new board coming also, says will be better and more reliable to handle the upgrades we put in it. Not sure how much truth is in that.

well i just had a brainfart and fried mine on the rewire for new pics and clearer instructions so…

ordering another.

its been a long long week :frowning:

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You are definitely a true addict Hammie! badluck laughing%20(1) rofl


Owning Gel Blasters is akin to owning a boat… endlessly tossing cash away… dizzy


Ironically it was an already functional solution before I decided to tidy it up too

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Oh no. Care to tell us what caused it.

A brain fart

Attached the signal line to the wrong pad

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Hey there, would this work for the m4ss as well? I’m looking at putting a 11v battery in the m4ss but have heard it will fey the fire selector board / mosfet most of the time…

Did you have a rough circuit diagram to help understand where you have soldered everything?

now…this is why i withdrew the original post

it was extremely board specific.

there is no real reason it can’t be done for the m4ss…its a matter of understanding what’s being switched, where and getting on with it.

my previously working solution was done with a couple of component fets and my intended update to my working solution desired an active brake…because i can…

having borked that in a moment of muppetry…

the coming how to will approach the task from an understanding perspective and show you how to find the information you need to do the task correctly rather than a take this coloured wire and dooo…

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Thanks for the response! I look forward to the tutorial.