Featured Help figuring out g&g prk9 mosfet issue

Discussion in 'Gun Building, Modifications & Repairs' started by Mike223, Nov 24, 2021.

  1. wetpee

    wetpee Active Member

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    This is specific to certain types of mechanical switches. The G&Gs in particular are quite bad according to Ben, and I can make a pretty accurate guess as to what the inside of the switch looks like by his description of the issue, but there are others. The sad part is the design might not even necessarily be the issue, but the materials used inside the switch. Nearly all aftermarket Electronic Trigger Units (ETUs) use a more reliable design. As long as the name is reputable, you pretty much don't have to worry about. The Gate Titan, Gate Aster, and Leviathan Optical use optical sensors that are virtually indestructible in normal usage because there is no mechanical wear occurring between the two elements. The trigger simply floats above the sensors, which shine a light at the trigger and determine its position based on the amplitude with which the light returns to the sensors. Wherever the trigger is, the light will shine back more intense because it is close than the other wall of the gearbox shell.
    The Perun Hybrid uses a magnetic trigger sensor that works quite well and is a good budget option for replacing a less than spectacular trigger unit.
    Note the difference between a MOSFET and an ETU. ETU refers to something that replaces standard trigger contacts and can have many programmable features. A MOSFET is specifically a single component that typically exists on those circuit boards, or can be a standalone unit, that directs the high current electrical flow to the motor only. High current is not necessary to run the other components on the board, and in fact, would damage them. The main reason high current can damage trigger contacts though is because the electrical "pressure" is so high that it is ready to jump before the contacts actually make contact with each other, causing an arc through the air that will burn up the surface of the contacts with each activation.
     
    Last edited: Nov 26, 2021
  2. OutlawAirsoft

    OutlawAirsoft Active Member

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    I always rewire my guns for 11.1v lipos, but then again I am comfortable repairing whatever damage it might cause. It can be a toss up though, because a stock gun may or may not be able to handle an 11.1.

    Essentially, all a high output lipo does is increases the rate of fire and trigger response, sometimes at the cost of various internals. Sometimes and fairly rarely, it can result in arcing across the trigger contacts, but a simple mosfet would fix that.

    You can look further into the possible internal consequences, like a prematurely worn piston or gear set, but most of these problems would be a result of everything moving faster, which puts more stress on some components.

    The main cause of stress is pushing your gearbox to the limits with a high output battery, which a lot of us try to do anyway. It all comes down to wether you want your gearbox to fail after 10,000 unimpressive shots or 5,000 impressive shots.
     

  3. Mike223

    Mike223 Member

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    The gun I made the post about, the g&g prk9 has whatever adjustable mosfet it came with stock which I would assume is made by g&g. I have another g&g with a gate titan however, but that’s not the one with the issue. It’s good to know it’s just the g&g mosfet and I can use a different option if I’d like.
     
    Last edited: Nov 26, 2021
  4. Mike223

    Mike223 Member

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    Ok, Thank you that clears everything up and I understand now.

    It sucks that their design sucks but it is what it is and I don’t need one for the gun. And if I do put a new one in at least I can have confidence I won’t have the same issue.
     
  5. OutlawAirsoft

    OutlawAirsoft Active Member

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    The Gate AXR is a good example of a simple mosfet, is doesn't have any features beyond just protecting the trigger contacts and diverting more power to the motor.

    Basic mosfets do two things:

    1) Protect the trigger contacts from electrical arcing by only running a signal (very low voltage and amperage) current through them. When it senses that the signal circuit is complete (the trigger is pulled), it closes or opens (depending on the mosfet type) another switch capable of handling much more voltage and amperage.

    2) Mosfets actually divert more power to the motor then standard trigger contacts, because the current no longer has to flow through the thin contact plates, which provide a little bit of resistance. The difference may not be noticeable in most builds, but it is there.

    Mosfet chips are usually used in conjunction with shottkey diods and resisters to perform these things as efficiently as possible.
     
  6. aotsukisho

    aotsukisho Well-Known Member

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    The Imax B6AC is a solid charger and is even on Amazon. This will reliably charge (and discharge) almost all common battery chemistries, I use mine from time to time to maintain the battery in my 4Runner.

    The lipo alarm is a good idea if you're worried about over-discharging, although once you are used to how your AEG performs it will be very obvious to you when the battery is near dead as the noise it makes will change.