Featured Mosfet Techinf Help?

Discussion in 'General Airsoft Discussion' started by Harry Arnold, Apr 15, 2018 at 3:49 PM.

  1. Harry Arnold

    Harry Arnold New Member

    So I just finished installing a nukefet, my first time installing a mosfet, everything had gone pretty well, followed the instructions they shown.

    However, when I go to plug my battery in, it sparks a little bit and the gears move and pull the piston back in little increments.
    I have checked the trigger contacts and they are not touching each other so I’m not sure where to go from there.

    Any help would be appreciated :D

    Below is a pic of the wiring, I have took most of the shrink wrap that I had used off. image.jpg image.jpg

    Attached Files:

  2. -Spitfire-

    -Spitfire- Well-Known Member Supporting Member


  3. BOA_SP3CT3R

    BOA_SP3CT3R Well-Known Member

    Mountain Home
    I had that happen(without a fet) once, the trigger trolley barely made any contact with each trigger pull, so a complete cycle took 3-4 trigger pulls. I fixed it by bending the contacts closer so they made full contact.
  4. Harry Arnold

    Harry Arnold New Member

    Nuprol 9.6V 1600mAh
  5. Harry Arnold

    Harry Arnold New Member

    That actually sounds really similar to what it’s trying to do, although I still don’t get why the gun wants to fire as soon as the battery is in without the trigger being pulled...

    Thanks for your reply though, I’ll give that a go :)
  6. -Spitfire-

    -Spitfire- Well-Known Member Supporting Member

    If it's firing without the contacts... contacting, the fet is likely fried out or incorrectly wired. Also, you should use a decent lipo... That Nimh is way underpowered.
    Harry Arnold and BOA_SP3CT3R like this.
  7. Harry Arnold

    Harry Arnold New Member

    That’s what I was afraid of :(, I’ll try it again with my LiPO tomorrow. I’m hoping it’s not fried since I followed Nukefets Guide .
    If it still doesn’t work I’ll triple check the wiring to make sure it’s in correctly. if that still doesn’t work, I’ll just have to buy a new fet . The complete one this time haha
    -Spitfire- likes this.
  8. Sitting_Duck

    Sitting_Duck Active Member

    F**k me how much solder did you use at switch ?????

    no offense but think you have used two three times the amount needed

    That mosfet signal wire - jeeeeeeeeeeeeez


    Also - me personally I'd run two wires down the back dedicated to motor
    Then use 2 x 24awg wires to trigger switch
    positive supply & return signal to mosfet
    plop the 24awg in a bit of shrink tube, superglue it to box by motor entry
    (so it doesn't move/catch)

    Might need a tiny bit of filing by rear of box on top side of gearbox
    then two wires can pass through same rear end of box/pistol grip

    Mosfet - soldering - most of this is down to careful planning of wires
    and neat soldering at joints
    But most of this boils down to neat wiring layout/planning and clean joints
    (without a ton of solder)
    Cut, shape wire(s) into place, then a quick tzzzzzzzzt and all job done neatly
    common sense insulation etc......

    but most of it is down to neatness to avoid risks of shorts
    ps - your soldering to deans connector is terrible
    way too long exposed wires no insulation
    no offense but your soldering technique needs a good deal of improvement

    I'd say clean up that trigger solder points
    99% of mosfet shorts are down to user error/issues

    Also - those trigger contacts - look a bit odd in pic
    have the winged tabs burnt off, they don't look flared like normal
    might be pic, but wondering if they burnt off a bit already
    (should be ok-ish but just saying it looks a bit messy in parts)
    Last edited: Apr 15, 2018 at 7:57 PM
    -Spitfire- likes this.
  9. -Spitfire-

    -Spitfire- Well-Known Member Supporting Member

    @Sitting_Duck I am never letting you see any pics of my soldering. Lol
  10. Harry Arnold

    Harry Arnold New Member

    Yep my soldering is dreadful, I ain’t ashamed ahahah, it is my first time doing it tho ;)

    Thanks for the mad detail in your reply btw, appreciate the feedback <3
    -Spitfire- likes this.
  11. BOA_SP3CT3R

    BOA_SP3CT3R Well-Known Member

    Mountain Home
    Me neither lol. I'm not too good but somehow managed to wire one of my 7.4's to micro deans.
  12. Airborne101

    Airborne101 Well-Known Member

    Learn to use flux guys. It really helps in making smaller and cleaner solder joints.
    -Spitfire- and Sitting_Duck like this.
  13. Sitting_Duck

    Sitting_Duck Active Member

    I'm not brilliant - far from it
    But ye olde psx's - well I killed one or two modding them
    All because I "thought" I could fit a modchip but ended up rewelding the pcb
    surface mounted resistors came off, tracks lifted - it was an abortion or abomination

    Turns out dollar tree or poundland solder and a 40w fat screwdriver tip is not ideal

    In the end you need a 20w to 25w for small intricate stuff
    And perhaps 35w to 40w for other stuff like deans

    Solder - makes a HUUUUUUUUUGGGGGGGEEEEEEEE difference too
    lower melting point solder for intricate stuff/pcb's means you don't melt everything
    (waiting for much higher temp solder to melt means everything but the solder melts)

    Flux - even if your solder has flux rosin core, it doesn't hurt to use flux
    just a dab wipe off excess and you get a great ttttzzzzzzzttt job done

    flux paste or a flux pen, flux/wipe, tin wire(s), tiny dab of flux/wipe
    solder wire to contact/spot - tttzzzzztttt, away with iron, hold wire 1 sec

    The problem all comes down to cheapo crap in the end
    decent solder - can't stress this enough
    25w iron with fine tip - heck my tip gets burnt out I just file it into a point
    (I've know people to use a medium size nail cut up for a tip)
    Flux if possible like I said

    (On console stuff - Kynar wrapping wire than keep using any old wire around)

    Routing wires & planning - goes a long way to avoid potential headaches too

    If do a rear wired gun often I'd go as follows.....

    Lay down 2 x 24awg trigger wires first at back channel of box
    Then lay down red positive wire first over the two trigger wires
    Finally lay the black negative wire last
    (may have to slightly file top of box to allow both wires to poke through)

    At the grip - motor's posi terminal is closest to trigger
    fit black negative wire to motor first
    then red posi wire goes over the connected negative wire then up to posi terminal

    The motor's 2.8mm space connectors can weaken when bent to shape
    So a dab of solder at the 90° elbow inside/outside
    HOLD CONNECTOR UPRIGHT - or solder runs into connector and won't fit on motor
    Just a dab or drizzle to ensure it doesn't blow like a fuse under high amp draw

    Switch wires - measure a little over after routing wire there abouts
    strip off say 10mm of insulation & tin the wires
    cut back the wire to say 2mm to 3mm max - just enough
    shape the wire perfectly - or as near as damn it before you pick up iron
    work out which one to solder first than leave you painted in a corner
    (in other words first wire now gets in way of last wire)
    Often you don't always need to remove safety arm in most cases
    (depends on switch though)
    The wire is already shaped into place, so just a finger to steady
    quick tzzzzt, away with iron, hold 1 sec - job done
    repeat for second wire, tzzzzt - finished
    off cut of old reg wire in channel by switch to squish trigger wires down

    reassemble rest of box/gun

    solder on connectors at final assembly of grip/motor plate
    check nice contact and how wires lay etc.....

    Deans - higher temp iron with say small chisel type tip if possible
    but most is all about tinning the deans & wires
    if possible a bench vice is great for steadying the connector to solder
    but I've taped the connector (I use a set/pair of deans to ensure no moving/melting)
    I've taped the connector to bench, or in some grips and then taped to bench
    Anything to keep the sod still so I can hold the wire steady when soldering deans

    Most of this crap is planning and finding a technique that works for you
    Use decent stuff like solder as explained and a bit of practice really

    Decent materials/tools for the job is a big major help
    Proper plan in routing the wires etc.... will save you a lot of stress too

    If you want to see poor planning and like a laugh then google:
    " Australian bricklayer accident report "

    If you reach the end without hysteria then you need to check your pulse
    (I think you might already be deceased)

    Hope some of this helps - not written in stone but sort of what I do at times
    (not bricklaying though - I know my limits)
    Last edited: Apr 15, 2018 at 10:27 PM
    BOA_SP3CT3R likes this.
  14. Sitting_Duck

    Sitting_Duck Active Member

    ^^^ THIS ^^^

    Some people say you shouldn't need it if using decent solder....
    But it REALLY helps
    (Don't boat it on, so every finished joint is more yellow than a lemon)
    just a dab or wipe is all you need - but it draws solder to solder/copper
    and it REALLY helps....
    Last edited by a moderator: Apr 16, 2018 at 4:42 PM