A&K M249 Auto Winding Box Mag fault

[DanP27]

Hi all, 

I am hoping someone can help me.

I bought an A&K M249 second hand from someone a little while ago (tested it on collection and all worked ok). I then took the gun out to my local field for a game day and half way into the second game the auto winding box mag stopped winding. I assumed at the time it was nothing serious and would investigate when i got home. 

I have now finally made time to investigate why but I've never done this kind of thing before. I have changed the batteries (AA's) and checked none of the wiring is loose, however it is still not working so i am stuck. 

Can anyone offer up any solutions/advice?

Thanks

Dan

View attachment 42977

 

[DanP27]

in case it helps, I've attached another photo after taking the mag apart a bit more in the hope to find a jam which has not worked out for me. 

View attachment 42978

 

[Iceni]

What is your level of electronics knowledge?

Do you own a multimeter?

It's hard to diagnose electronics if you don't have a multimeter. Because in a case like this the first thing you do is check each wire for continuity. Look for cold solder, and make sure the whole unit is intact.

By intact I mean visually look at everything. There should be a spring for both batteries, and a contact bar acting as a bridge. You should check the battery circuit is making 3v, then make sure you are getting 3v at the +v input.

The next thing to do is check the switch for much the same, Continuity to the ground, Continuity in switched positions, Continuity in switched positions to PCB.

After that it's a series of investigations:

Bridge the Mic.
Put 3v on motor
Check rest of cables

Check PCB resistors.
Check PCB diodes.


At that point, if it's still not showing a fault it's scrap.

If you can't follow that or don't have access to a soldering iron and multimeter then it's not worth even looking into the investigation stage. Checking the battery bridge and changing the batteries is about all you can do.
 

 

[Podge1945]

I had the same fault with my first box.

Turned out it was a fault on the board, I was lucky that I had it replaced but I would look up a&k 1500 box mag on Amazon I found them for £50 with shipping which is still £50+ cheaper than getting them in the UK. They are a great addition so much smaller and easier to use and a rechargeable battery. Love mine works a gem.

 

[DanP27]

What is your level of electronics knowledge?

Do you own a multimeter?

It's hard to diagnose electronics if you don't have a multimeter. Because in a case like this the first thing you do is check each wire for continuity. Look for cold solder, and make sure the whole unit is intact.

By intact I mean visually look at everything. There should be a spring for both batteries, and a contact bar acting as a bridge. You should check the battery circuit is making 3v, then make sure you are getting 3v at the +v input.

The next thing to do is check the switch for much the same, Continuity to the ground, Continuity in switched positions, Continuity in switched positions to PCB.

After that it's a series of investigations:

Bridge the Mic.
Put 3v on motor
Check rest of cables

Check PCB resistors.
Check PCB diodes.


At that point, if it's still not showing a fault it's scrap.

If you can't follow that or don't have access to a soldering iron and multimeter then it's not worth even looking into the investigation stage. Checking the battery bridge and changing the batteries is about all you can do.
 

I had the same fault with my first box.

Turned out it was a fault on the board, I was lucky that I had it replaced but I would look up a&k 1500 box mag on Amazon I found them for £50 with shipping which is still £50+ cheaper than getting them in the UK. They are a great addition so much smaller and easier to use and a rechargeable battery. Love mine works a gem.

Thank you both for your advice. Electrics are not something I know much about and so I am going to either leave this to a side to look at another time or maybe take it into a shop that hopefully wont charge much to do an initial assessment.

I think I'm going to buy the 1500 box mag though thanks