View Full Version : Fuse blowing on trigger pull...

11-29-2004, 03:34 AM
Two nights ago me and ap0gee were playing near my house, and at the end of the night I was popping bb's at him when my AUG starting sounding funny and the next shot it stopped firing. Checked the fuse, it was blown. I replaced it and put in a fresh battery, and it blew the fuse immediatly.

Last night we took apart the gearbox, only to find that my Systema Poly piston had cleanly snapped off it's first tooth - the METAL one - and the piston head somehow disassembled itselft inside the piston (which I fixed). You can also see a "line" perfectly straight down all the piston teeth, like it was only wearing at that certain spot on every tooth.

After getting the stock TM piston and reattaching the piston head, we checked the gear shimming. The gears seemed to have a little play (down the axle, when the gearbox shell is attached, you can push the axle back and forward inside the bushing a little bit). We re-shimmed the gears so there was no play. Made sure the only parts on the gears that touched each other were the teeth. All the bushings had 1 shim between them and the gear itself. After everything looked good, we reassembled the gearbox, tested the gearspin (which seemed okay at the time - they didn't spin "freely" but there was no catching/rubbing), installed all the internals back in, reassembled again. Of course we had to do this a couple times before it worked well.

Before I put the gearbox back in, I test fired a shot. Heard a split second "whirrr" and it popped the fuse. Tried again, no sound, blown fuse. :confused:

I still think it might be that the shimming is off. If anybody can give me some pointers for a v3 gearbox, I'd appreciate it.

edit: Well I found the AEG shim guide from the faq. Good guide, will go by it tomorrow when we tear it apart again. :D

11-29-2004, 08:40 AM
the piston head somehow disassembled itselft inside the piston Make sure you really tighten the piston-head screw in place.....and better yet is to use loctite on that screw.

11-29-2004, 10:09 AM
Ditto what Wolv said. It is absolutely critical to use loctite on the piston head screw, because it WILL come off if you don't... sooner or later.

Also, is the battery charged? My AUG is notorious for blowing fuses when the battery is getting low. This is a 9.6V 1500mAh battery. When NiCds start getting low, they dump huge currents through the motor trying to keep the voltage high and can blow the fuse.

11-29-2004, 01:29 PM
Yeah, it's charged. That the first thing I checked after I replaced the fuse because my AUG has done that before as well. Unfortunatly this time things were a little more catastrophic in nature.

I think the piston head did disassemble because I didn't tighten it well enough. That's the only conclusion I can think of, it is not worn down at all. I just put it back together and tightened the screw REALLY tight...

Where can I pick up some loctite? Walmart have it? I hope so because that's probably going to be the only place open when I get off of work.

Then back to shimming...

11-29-2004, 01:56 PM
Wal-mart probably has some. Any hardware store would have it also.

12-01-2004, 01:55 AM
Good news, the AUG is back up and running as good as the day I got it. Shimming went perfectly, I thread locked the piston head screw, and now she purrs like a ferocious kitten. :D

Thanks for your help guys.