Trigger Switch Replacement...

[Docv400]

I've been wanting to try this out for some time now, but only just had an AEG in that needed it.

CYMA AK, the original contacts were just about shot, badly worn/burnt.

I'd MOSFETed this AEG a while ago, but without opening the box to do the contacts, that was 2 years ago and it's had a lot of use since.

 

First job, file down the contact block so it's approx 1.5-2.0mm proud of the housing.

I'm using a Printed Circuit Board (PCB) mount 'tactile' switch, 6x6mm square and approx 5mm deep inc button...

The contacts are paired, so I bent them together and soldered a wire to each pair.

 

Then it's just put in place in the main housing and epoxied in place.

I placed it so it's contacted by the trigger block at around mid-travel of the block, you could place it further forward if you wanted a longer trigger throw.

It needs to be far enough forward however to make sure the semi cut-off lever lifts it cleanly without slipping past it.

A is fully rearwards, B is point of contact, C all epoxied in place.

Obviously this will only work for MOSFETed AEGs, and ones that have this trigger contact arrangement, so mainly V2/3, but may be adaptable for other types with a bit of thought/work.

Only around 20p each too.

[P.S.I.]

Thanks for this.

I was thinking about trying something like this myself, but I've been waiting for a trigger switch to fail in something.

My idea involved a different type of switch, but I think the one you used is a better choice.

[Docv400]

My original idea was to use a micro-switch, the ones in a mouse are small enough, but these are the perfect size and shape really.

There's plenty of choice in button lengths as well.

[Bersy]

Doc have you got any links to were we can pick these switches up from? interested in trying it out myself to be honest

[DarkLite]

I did this with a tiny microswitch in my AK, seemed to work quite well. I'll see about getting some pictures up.

[Utty]

Interesting, I need to try this sometime.

[slacky]

Doc have you got any links to were we can pick these switches up from? interested in trying it out myself to be honest

 

http://cgi.ebay.co.uk/Tactile-Switch-6x6mm-Height-4.3mm-Pack-of-5-IN-UK_W0QQitemZ250520284261QQcmdZViewItem?rvr_id=&rvr_id=&cguid=fa7777641260a0e202a26e42fec7a6f0

 

As doc mentioned, you can get ones with a longer or 'taller' button.

 

Always thought of this but unfortunately I dont have the motivation to try it. Thanks for sharing Doc.

[Bersy]

Cheers slacky, might give it ago and see what i think, is there much force needed to push the button in?

[aznriptide859]

Nifty idea , any idea for smaller switches for V2 GB's?

[DarkLite]

Cheers slacky, might give it ago and see what i think, is there much force needed to push the button in?

 

Depends on the switch, but it shouldn't need much pressure at all.

[Docv400]

I got some yesterday from RS Components...

Switches

Their delivery rates are silly, so collect from a trade counter, or use e-bay.

E.G.

You need the 'through hole' mounting type, surface mount ones don't have the long 'legs'.

Go for 'washable' rated ones if there's the option, they're sealed better, you don't want the epoxy you use to get inside, or any grease/oil/c##p from the gearbox.

 

Operating force for most of them is around 1-2 Newtons, a tiny bit more than it takes to press a key on your keyboard.

You can just about feel the switch operating through the trigger, it's that light.

[Docv400]

Got this AEG back together on Friday (7th) and it works beautifully

It was used all day at a game on Sat and never missed a beat.

[Tacitus]

That looks awesome. I might have to try it...

[Docv400]

Nifty idea , any idea for smaller switches for V2 GB's?

 

 

Read on...

 

 

Finally got round to doing a VerII.

You can see there's not so much room for the switch as with the VerIII, but it does fit...

I had to take a tiny amount off the underside of the top section of the trigger block, so it doesn't catch on the switch body.

Also, had to cut out a small recess in the main housing, so the switch sits far enough forward. Didn't take a shot of that, but will be obvious if you do one.

 

 

As with the VerIII, you need to shorten the contact block itself.

The securing pin is in a 'blind' hole (only open one side), so you need to carefully drill through from the blind side to remove it, or you could probably push it out by just pushing a scriber through the closed side...

Switch in position, ready for epoxying.

If you do one, out all three parts together and hold the trigger block tight against the switch (elastic band or tape) while you apply the epoxy (be careful to keep the epoxy away from the trigger block of course), that way it'll all line up perfectly when it's done.

 

 

All in place, you can see in the R/H pic where the housing has to be trimmed for the switch to sit, the web at the switch's bottom edge.

 

[Docv400]

...

I had to take a tiny amount off the underside of the top section of the trigger block, so it doesn't catch on the switch body...

Forgot to mention, you'll also need to take a little off the corner below the return spring hook 'pegs', otherwise the trigger block may bind on the switch when it's released (back end lifted) by the Semi cut-off lever.

 

 

 

[Docv400]

Finally got this box back together a few days ago (the owner couldn't decide what other work he wanted doing), only to find it won't fire semi, it fires auto in the semi setting.

The cut-off worked OK when I checked it manually before assembling the box.

I've not had a chance to investigate it yet, so I don't know if it's anything to do with the positioning of the switch, or some other cause.

 

I had to fit a replacement contact block stop post, as the original had broken off, but it won't be anything to do with that.

[Utty]

My guess is the contact block hasn't been shortened enough.

 

I've just done this mod on a V2, it looks identical to yours except:

 

- the wires go out the bottom through a hole, instead of out the side;

- the contact block is shorter, almost flush with the plastic carrier (like on the V3 you did).

 

I haven't received my mosfet and other new mechbox parts in the mail yet, so I can't say if this actually works yet.

[Docv400]

That's what I'm thinking too, but it can only be a matter of a few thou, as it worked manually when I checked it.

I'll let you know as soon as I strip it down again.

 

[Utty]

Done!

 

Mine does full auto with the selector switch set to semi, too.

 

However, this mechbox was doing the exact same thing before this project. I blamed the trigger contact as it seemed deformed, but the cutoff lever did look a little worn. Maybe this is the problem? I guess there's only one way to find out.

 

Edit: replaced the cutoff lever. Didn't help! Conclusion: I'm stumped.

[Utty]

On mine, when the contact block is activating the microswitch, it is in the exact same position as a full trigger pull with the regular contact, and the cutoff lever is able to lift the contact block off the trigger when testing manually.

 

AHA. I just tested manually again - the rotating sector gear does indeed make the cutoff lever lift the contact block off the trigger - when the sector gear isn't shimmed. Stacking the needed number of shims under the sector gear somehow lifts it almost clear of the cutoff lever; it activates, but not enough to lift the contact block. Hmm.

 

 

As for the idea of the cutoff lever activating a 2nd microswitch set to break the circuit instead of mechanically lifting the contact block: sure, but wouldn't the 2nd microswitch get activated constantly when switching to full auto, thus turning full auto mode into dead gun mode?

[andyb223]

 

As for the idea of the cutoff lever activating a 2nd microswitch set to break the circuit instead of mechanically lifting the contact block: sure, but wouldn't the 2nd microswitch get activated constantly when switching to full auto, thus turning full auto mode into dead gun mode?

 

no, when the selector is switched to full auto it "holds" the cut off lever open so that it never cuts off the trigger contact

[Utty]

no, when the selector is switched to full auto it "holds" the cut off lever open so that it never cuts off the trigger contact

Yes, thus continously pushing the hypothetical 2nd microswitch which is set to break the circuit when pushed. Thereby turning "full auto" into "no shooty".

 

 

In any case, I've added some material to the side of the cutoff lever where it interfaces with the sector gear, hopefully solving the problem. I wonder if Doc's semi auto problem is equally unrelated to the microswitch mod.

[Utty]

Well it worked, everything works perfectly now. Now for the rest of my guns!