ASG Sten Gearbox Malfunction

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Kendo
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ASG Sten Gearbox Malfunction

Postby Kendo » Sat Apr 01, 2017 6:05 pm

Hi all,

Hoping one of you is technically minded, as I'm not sure where to start. Last time the Sten was out was last year, and I was having an issue where I'd pull the trigger and the gearbox wouldn't cycle - it would sound like it was winding up, then 'choke' and stop. If I recall correctly, it would only manifest when firing very short bursts; longer bursts seemed less prone to this stoppage.

Identifying this problem would be a good first step before I crack anything open, and I'd appreciate if anyone could help.
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Re: ASG Sten Gearbox Malfunction

Postby Lord Elpus » Sat Apr 01, 2017 6:44 pm

Sounds like battery can't cope, is it a good one? Could be weak motor.
But.....saying that it might have to come apart if something is partial seizing, piston, tappet bar, or even a dry bearing. Spray in some silicone into the gearbox perhaps through the trigger top, see if it runs better for a while, that's not a cure, just an indicator to see if you have seizure problem.
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Re: ASG Sten Gearbox Malfunction

Postby dadio » Sat Apr 01, 2017 7:06 pm

It could be the trigger itself , it's kind of a crappy design and the trigger actually makes the electrical contact of the switch and as it's alloy (pot metal at best ) it can become eroded or carboned up .
armoury
m1a1 Thompson,sten mk2,mp40,stg44,sterling,mk2 bren gun,lee Enfield no4 mk1,Mauser Kar98, Walther ppk,smith and Weston m10 and Mauser m712
Give me a big enough hammer and a place to stand and I could fix the world.
i'll kill a man in a fair fight or if i think he's going to start a fair fight or over a woman or.......
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Re: ASG Sten Gearbox Malfunction

Postby Kendo » Sat Apr 01, 2017 9:28 pm

Lord Elpus wrote:Sounds like battery can't cope, is it a good one? Could be weak motor.

It's a good quality set of lipos that I've used for years. Never gave me a problem 'til now, and they still chug along just fine in every other AEG I own.

dadio wrote:It could be the trigger itself , it's kind of a crappy design and the trigger actually makes the electrical contact of the switch and as it's alloy (pot metal at best )

I did not know that, though I'm hardly surprised. I did suspect the trigger contacts might be at fault, and I debated with myself about the thread title ('motor malfunction, or trigger?').

Is there a fix? Can you just clean up the contacts and be on your merry way, or am I looking at a replacement?

Appreciate the responses, boys. :good:
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Re: ASG Sten Gearbox Malfunction

Postby Lord Elpus » Sun Apr 02, 2017 8:04 am

If it is trigger contacts, yes they can be cleaned of carbon deposits, but seeing as you have to strip the whole thing to get to them, you might as well fit new,..... and if you fit a mosfet, you won't get burnt contacts, it could be your lipo's doing that, what voltage are they?
Usually 7.4v won't do any harm to contacts, 11.1 v lipo' eventually do. Cheap mosfet from someone like "airfet" about £19, dead easy to fit.
While it's apart, rebuild the whole thing!
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Re: ASG Sten Gearbox Malfunction

Postby Kendo » Sun Apr 02, 2017 2:18 pm

It's a 7.4, mate, avoided the higher voltage for reasons of wear and tear. Been using them for years though, so may well have taken its toll, finally.

Is there any guides for fitting a mosfet you can recommend? Might as well give it a shot, seeing as it looks like I'll be cracking open the gearbox anyway.
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Re: ASG Sten Gearbox Malfunction

Postby dadio » Sun Apr 02, 2017 3:30 pm

If you get an airfet MOSFET off eBay then they come with instructions to fit , i fitted copper contacts to the trigger on a sten a while back and that solved the problem as well.
armoury
m1a1 Thompson,sten mk2,mp40,stg44,sterling,mk2 bren gun,lee Enfield no4 mk1,Mauser Kar98, Walther ppk,smith and Weston m10 and Mauser m712
Give me a big enough hammer and a place to stand and I could fix the world.
i'll kill a man in a fair fight or if i think he's going to start a fair fight or over a woman or.......
a problem shared is a problem halved ,but an advantage shared is no advantage at all
if a job's not worth doing then its certainly not worth doing well

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Re: ASG Sten Gearbox Malfunction

Postby ww2stu » Sun Apr 02, 2017 7:16 pm

My sten broke down on the open Day where we all met up. The spring had made a cut into the spring guide and got stuck! Never seen that happen before a new steel spring guide was all that was needed. Hope yours turns out to be an easy fix.
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Re: ASG Sten Gearbox Malfunction

Postby Lord Elpus » Mon Apr 03, 2017 6:28 am

As dadio says, the mosfets come with instructions.....if you can solder a wire, ......you can fit a mosfet, I've got a "burst wizard" in my Sten, which is bigger in size than the airfet, so there's plenty of room.
I've seen broken plastic spring guides, not seen one that the spring has cut a groove! did it jam? or just not fire the bb,s?
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Re: ASG Sten Gearbox Malfunction

Postby Kendo » Thu Apr 06, 2017 9:55 am

Thanks for the quick and thoughtful replies, my dudes. Plan on picking up a mosfet now, but I'll be having someone else do the fitting, as my last venture into soldering went awry. :oops:

EDIT: Actually, Airsoft World do a Burst Wizard 'plug-and-play' mosfet. It looks like it acts as a bridge between the battery and motor. Would this be sufficient for the Sten, do you think?
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Re: ASG Sten Gearbox Malfunction

Postby Granger » Thu Apr 06, 2017 4:33 pm

You'd have to actually wire the mosfet in to protect the trigger contacts.
Regards,

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Re: ASG Sten Gearbox Malfunction

Postby kingmaker » Thu Apr 06, 2017 6:24 pm

Hi thats correct,with the burst Wizard in plug and play mode you can only use some of the fire control features,the main high current is still passing through the trigger switch.
If you re wire the gun,the mosfet is then the trigger switch with the high amp current,the old trigger switch is then only a signal switch for the mosfet,and only has to handle very low amps,and so will not degrade due to arcing.Also you will get more shots out of your battery to due the increased electrical efficiency.
Some of the ready made mosfet fire control units get bad reviews as the electronics fry themselves quickly,personally i use an international rectifier 3034 mosfet from RS Components,which costs £1.50. Solder the 2 resisters it needs to make it work,about
20 pence ,however you don't get any fancy fire control features with this set up.
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Re: ASG Sten Gearbox Malfunction

Postby Lord Elpus » Sat Apr 08, 2017 7:52 am

You'll have to put up wiring schematics for that Kingmaker, sounds interesting, I would like to have a go. How does the sizing compare? Does it work out as compact as the Airfet?
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Re: ASG Sten Gearbox Malfunction

Postby kingmaker » Sat Apr 08, 2017 4:03 pm

Hi if you google' airsoft mosfet diy 'in google images Lots of circuit diagrams will come up,there are several sites with build guides.
I got mine of Airsoft Forum .com and American site. Try this

http://www.airsoftforum.com/board/topic ... t-mosfets/

Personaly i did not put a 5KP18a diode on mine seems ok without but it does protect the mosfet.
Rs components are good for small online orders now. Make sure you get the international recifier 3034 mosfet for reliability.

People building oversize battery packs for Vaping use 3034 mosfets and they are on ebay and cheap but a low price chinese mosfet is not worth a dam and will blow.
I bought 4 mosfets and 10 of each of the 2 types of resistor so if you do get one go bang you have a spare on hand
It is reasonably compact,,not as small as a gate nano but smaller that the. Other gate products
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Re: ASG Sten Gearbox Malfunction

Postby kingmaker » Sat Apr 08, 2017 9:41 pm

I expect the airfet will use similar components to the guide i have sent a link to on airsoft forum(usa) its just very well finished of compared to most home done stuff.
So yes if you do it yourself it will be a similar size to the airfet.
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