Solved - TM Mp5 High Cycle Trigger Problem

[Ben Savage]

Hi all, I've had the Tokyo Marui MP5 High Cycle for a few years now, but around 2 years ago before I had a break from airsoft the gun started to have some issues which I have no clue how to fix, due to my lack of technical knowledge/experience with airsoft guns. 

The problem is that when pulling the trigger nothing happens, until I then apply quite a lot more force which pulls the trigger back to the very limit to which it can move and only then does it fire. This makes it entirely useless for taking to games as I can't reliably fire the gun. I think the problem has something to do with trigger contacts maybe, but to be honest that is just a complete guess.

Any help would be greatly appreciated, thanks.

 

[Asomodai]

Making a few logic jumps here. But it's likely trigger trolley not connecting to the contacts until right at the end of the travel. 

This happened on my T97 once where I just held down the full auto trigger on a test for a little too long and it MELTED the plastic around the metal contact on the trolley so much that the metal sunk into the trolley. So it wouldn't hit the trigger contact. 

So I reckon you need to either clean up or replace the trigger trolley and/or contacts. If you get a basic mosfet installed whilst its being fixed it can prevent the heat and carbon build up that causes this. 

 

[Skara]

replace the contacts and get a nice mosfet in there, preferably one with a double signal wire so that all the load is passed from the battery directly to the motor (that'd be a Gate NanoAAB/NanoHard/Merf3.2/Warfet)

 

[Rogerborg]

Yup, that's trigger contacts. The good news is that it looks like it has a standard(ish?) V2 trigger trolley.  The bad news is that it might be entirely standard.  You'll have to look and see.

So it's, er, "just" a case of taking it apart and seeing what's up with the contacts.  YouTube disassembly videos will show you how and you won't need anything more than small screwdrivers and Allen keys.  It's a bit intimidating the first time you pop your case cherry, but just keep the spring pressed down while you get the case apart and then get the tension off it as soon as possible.  Placing magnets on the underside of the case helps to hold everything in place while you re-assemble, but again being a V2 you won't need three hands to hold both the trigger and spring in place.

 

[Ben Savage]

So I eventually got around to taking the gearbox apart a couple of weeks ago, and found that the trigger contacts were covered in all sorts of what is presumably carbon or something like that, but the metal looked like it had slightly worn away. I reassembled the gearbox, and tested it after cleaning the carbon and checking that everything else doesn't look to be broken. Unfortunately the same problem occurs of the trigger needing to be pulled back all the way, so I'm assuming this is the result of the metal being worn down.

Now I can understand the basic mechanical functions of a gearbox (gears pulling piston back, spring sending it forward to compress the air and fire through the nozzle etc) but I really don't have an understanding of the electrical side of things, so I'm wondering what the best bet is as a replacement. I've heard lots of good things about the Gate Warfet, but I believe this is outside of the gearbox, so would I need to replace the trigger system with a replacement one that is the same type, or is there a part which is dropped in instead of the stock trigger section, which completes the circuit for the gun to fire?

I really don't know the electrics of airsoft guns well (a point made clearer when I put a 9.6 to test again instead of an 8.4 and I think I've managed to blow a fuse) so it would be great for any useful information as I've been struggling to find the exact details of what I'm trying to find out.

 

[Rogerborg]

I believe you've got a V2 gearbox, so this trigger trolley is likely to fit.  However, with it being airsoft...

https://www.ak2m4.co.uk/internal-parts/trigger-switches/ra-trigger-switch-v2-red

You'll need to sort that first, then think about a mosfet.  I'm not sure if you've got room for a warfet in there, I'll leave that for someone who knows.

 

[Ben Savage]

Ok thanks, ordered that and I'm hoping it works, and I didn't think about the fact that the warfet would be unlikely to fit, so I'll keep looking.

 

[Skara]

ordered that

Click to shrink...

You didn't tell us what exact model you have.

Is that a MP5K? an A5? because they have 2 different gearbox shells, and the V2 contacts you have ordered won't fit if it's the mp5k, which uses a V3 box.

 

[Ben Savage]

You didn't tell us what exact model you have.

Is that a MP5K? an A5? because they have 2 different gearbox shells, and the V2 contacts you have ordered won't fit if it's the mp5k, which uses a V3 box.

Click to shrink...

It’s the A5 so a V2 gearbox, don’t worry, thought I’d mentioned that already but I was sure to double check that they were for the correct gearbox.

 

[Skara]

It’s the A5 so a V2 gearbox, don’t worry, thought I’d mentioned that already but I was sure to double check that they were for the correct gearbox.

Click to shrink...

okay.

then you'll also have enough space for a warfet, depending on the physical size of the battery you use.

Hard wiring it is a piece of piss.

 

[Rogerborg]

then you'll also have enough space for a warfet, depending on the physical size of the battery you use

Click to shrink...

I reckoned so but didn't want to say for sure.

You can get a mosfet into an MP5K (V3 box, God awful V3 trigger) if you get the right battery and are careful with the wiring..

 

[Skara]

I reckoned so but didn't want to say for sure.

You can get a mosfet into an MP5K (V3 box, God awful V3 trigger) if you get the right battery and are careful with the wiring..

Click to shrink...

Heh the A5 has some space in the handguard, the K really needs a peq box unless you go for an internal unit like a Titan/Perun or a Jefftron thingy. Obviously clones of these units are fine too, like the aliexpress optical fet you shared not long ago.

 

[Rogerborg]

K is do-able but probably not with the 67mm long warfet.  I rewired to the rear and have a wired-in 30mm long mosfet and a 110mm long lipo in there with the wires cut short and one Deans connector between the mosfet and battery. There's some room to spare, maybe not the 45mm or so needed for a warfet plus another Deans plug though.

Anyway, academic, OP should be good to go.

 

[Ben Savage]

Final Update: Part arrived about 12 hours ago, and after teaching myself to solder (admittedly not well), the MP5 has now been fixed (although the pesky anti reversal latch came out of place 3 times during gearbox assembly without me noticing until testing), just currently without a MOSFET, but thanks a lot for all of the advice, great to have one of my best guns working again.

 

[Rogerborg]

Ace, top job.  Solder is as solder does, you'll only get better from here.

Those frikking latches though.  You can use a thin knife blade to hold them down, there appear to be tools available to do it  now, but I like to stick strong magnets under the gearbox, which also holds the gears in place and upright as well.