help with blown fuse

[Neurotrauma]

I just took apart my Sig 553 MAX G&G, and replaced my spring with a m100 instead of the m140. About halfway through the reassemble I tested my motor to ensure there was no issue and it spun when I pulled the trigger.

Upon completion of reassembly, I tried to dry fire with the handguard open and a green surge went across my fuse and severed the wire inside, I was wondering what the best solution is? should I just go out and buy a bunch of fuses and see if they blow when I test it again or should I try it with no fuse? I am worried about harming any parts.

I dont know what changed from me testing the motor to it being put back together but i dunno what to do.

[Spawn28]

sounds like a short in one of the wires upon reassembling the lower half you probably somewhere cut into or stripped a wire creating a short my sugestion would be unless you have electrical savy get it to a gundoc ASAP and dont test anymore fuses till the issue is fixed..

Oh yeah and please dont attempt to fix it with electrical tape it will just make things worse the next time around........trust me i have seen this done.

[CDN_Stalker]

Did you disrupt any of the shims on the gears while doing the spring change? What fuse was in there before the change? Do you feel the need to have a fuse? (........most don't)

Etc.....

[ILLusion]

Sounds like your motor could be connected backwards, causing it to try to spin backwards. The anti-reversal latch will block it, which would build up intense current draw, thus, blowing your fuse.

If it spun correctly out of the gearbox, but incorrectly once assembled, that could be it.

Are you sure your polarity is correct?

OR, it could be a short (as mentioned).

OR your motor height could be too tight. If the motor doesn't immediately spin when you pull the trigger, DON'T hold the trigger down!

[Neurotrauma]

I tested it once, with the fuse removed and the two halves connected, just one shot on semi to test the motor with it outside the handgrip, and it is still functionning. The polarity is correct, could I be putting the motor in the wrong way?

could it still be a short if its working with no fuse?

I dont think I moved anything with the shims??? only the first gear and the anti reversal latch came off and i put them back on as the video directed...

EDIT:
Okay so I've looked up shimming and it appears that I may have take two of the little washers thinking they were part of the trigger assembly and I put them as washers on that, I have no knowledge about shimming or anything so I guess its back to the research table, the other gears never fell out so Im not sure exactly where this came from.

[ILLusion]

Originally Posted by Neurotrauma

I tested it once, with the fuse removed and the two halves connected, just one shot on semi to test the motor with it outside the handgrip, and it is still functionning. The polarity is correct, could I be putting the motor in the wrong way?

The motor height could be too tight.

Originally Posted by Neurotrauma

could it still be a short if its working with no fuse?

No

Originally Posted by Neurotrauma

I dont think I moved anything with the shims??? only the first gear and the anti reversal latch came off and i put them back on as the video directed...

Did you check to see if they could spin freely after you closed up the box? (Do it with the spring removed)

[Neurotrauma]

I did one quick test with the motor in and the fuse connected and it sounded like the motor moved inside the box but no shot was made and it sounded like there might have been resistance.

is 2 shims enough to make a gun go from firing fine to not at all? I had no issues with motor height or grinding gears prior to this spring change, do I have to adjust motor height every time I take out the motor?

[ILLusion]

Originally Posted by Neurotrauma

I did one quick test with the motor in and the fuse connected and it sounded like the motor moved inside the box but no shot was made and it sounded like there might have been resistance.

That's not a good enough test. Test it BY HAND. It should spin freely.

Originally Posted by Neurotrauma

is 2 shims enough to make a gun go from firing fine to not at all?

YES.
In fact, ONE shim that's too thick is all it takes.

Originally Posted by Neurotrauma

I had no issues with motor height or grinding gears prior to this spring change, do I have to adjust motor height every time I take out the motor?

Only if you've changed the shimming, particularly to the bevel gear.

[Neurotrauma]

yeah if anything it was the bevel gear that they came from. If anything it wouldnt be too thick shims but thats good to know.

I will go back into the gearbox when I have more time, I am pretty new to airsoft and this is the first gun ive ever taken apart so I went really slow and freaked out a lot when stuff fell out like the trigger assembly and some other stuff that took me FOREVER to figure out how to get back in properly, this was literally an all day project for me.

When I've got some more time (and patience) I will give it another shot paying particular attention to the shimming, I keep thinking im gonna toast my gun or lose a little tiny spring or ball bearing or something, so I tried to move as little as possible, I'm just hoping I didnt lose any more shims those things are so tiny its possible one fell and i didnt notice.

I appreciate your help, any more tips would be appreciated as you seem to know what your talking about.

[Jsquared]

Hi, I experienced a similar problem with my ICS ak74. The gearbox is really tight and the wires have to slip behind it. When I put everything back together and tried to shoot I blew the fuse. Fuses are built to go when there is a short in the circuit. If the gearbox was working after you put it together before it was put back into the gun then your gears are fine. You have probably scraped the wire on the case and caused a short. Take the gearbox out and check over the wires, tape them where needed. You do not need to disassemble the gearbox again.

Cheers - Jsquared

[CDN_Stalker]

If the gears are too tight, more current will be drawn by the motor, which will cause the fuse to go. Fuses are current based, too much is the result of a short to ground or too much draw by the motor. Sounds like it is a shimming issue.

[ILLusion]

Originally Posted by Neurotrauma

yeah if anything it was the bevel gear that they came from. If anything it wouldnt be too thick shims but thats good to know.

I think you mis-read what I wrote. I did say that too thick shims WOULD cause your gears to seize up, which is the opposite of what you're writing.

Check your shimming. If it's too tight, it can draw additional current, which could blow the fuse.

Basic rule in AEG mechanics:
If you pull the trigger and nothing happens, LET GO OF THE DAMN TRIGGER! If it's not turning over, then something is wrong.

You're lucky the fuse blew. You could cause the battery to blow up or destroy your motor in the process if a fuse is not installed. If you don't know what you're doing, keep a fuse installed at all times!

[ILLusion]

Originally Posted by Jsquared

Fuses are built to go when there is a short in the circuit.

Fuses are built to open a circuit when current draw exceeds what is allowable. This prevents the load from burning out, melting the wires, or from destroying the power supply. It is a safety feature in the event of improper installation (such as a load with reversed polarity, a spring that's too strong, shimming that's too tight, etc), or a short in the circuit. Fuses are not just for potential short circuits.

Electrical shorts are just one of the many reasons why fuses or circuit breakers are used. It is primarily used to prevent additional damage.

[MaciekA]

Originally Posted by Neurotrauma

I will go back into the gearbox when I have more time, I am pretty new to airsoft and this is the first gun ive ever taken apart so I went really slow and freaked out a lot when stuff fell out like the trigger assembly and some other stuff that took me FOREVER to figure out how to get back in properly, this was literally an all day project for me.

When I've got some more time (and patience) I will give it another shot paying particular attention to the shimming, I keep thinking im gonna toast my gun or lose a little tiny spring or ball bearing or something

Feel free to post pictures and ask more questions on here. The shimming process is actually pretty easy with regards to knowing if you've shimmed too much or too little. If you're feeling up to it, you could use this as an opportunity to learn how to shim. You've gotten this far pretty good... Might as well dive in.

My preferred method for shimming has become the start-with-the-bevel-mesh method:

1) take out and place aside: gears and shims, anti-reversal latch, cylinder, spring, piston, spring guide, tappet plate + nozzle, tappet spring and trigger. Have a bowl where you put all this into so you don't lose it. Make sure to have some extra shims around with a good variety of thicknesses. Have some gear grease available (100% silicone)

2) attach motor grip to HALF of the shell of the gearbox (the half that doesn't have the trigger assembly connected to it). Leave the other half of the shell aside. Place the bevel gear into the gearbox. Put motor into motor grip and seal the grip, adjust the height of the motor to meet the bevel gear and get a nice mesh. Add thin shims under the bevel (but not on top) until it has good contact with the motor's pinion gear, but not too much. Re-attach the other half of the shell, detach motor grip. Check with your finger or a tool that the bevel spins freely. Now shim the *other* side of the bevel now until it still spins but with no play along the axle axis. Make a note of the shimming on bevel in case you accidentally knock it off or things drop off later.

3) Now work with the other half of the shell the way you would normally. Shim the bottom of the spur gear just enough off the shell for no contact with the shell, but maximum transmission with minimal contact to avoid grinding and noise. Once you have it at the right height, seal up the gearbox (with screws!) and try spinning the bevel again and watch the spur to see if it's still spinning well. It will probably have a tiny bit of play, so now you can add shims on the top. Keep re-assembling and checking for play and a decent amount of free-spin.

4) Repeat with sector gear and the appropriate transmission between sector and spur. Reassemble again (with screws!) and check spin+play with your finger.. Add shims on top. Check again. Make sure the sector gear is not touching the cutoff lever.

5) Stage the piston in a spot where you can check that the sector gear isn't shimmed too high to engage the piston teeth. It's easy to forget this.

If you can balance play vs. spin, you should end up with minimal noise and minimum possibility of lock-up. Don't forget to seal up the gearbox with screws each time, testing without sealing can fool you into thinking you have a good shimming only to find out after sealing that it's too tight.

Hope that helps. It'll take 30-45 minutes to get this right for the first time but it's totally worth it and you can feel and hear the difference, and your motor won't have to work as hard to pull the piston.

EDIT: one more thing. I take pictures at every stage in addition to the notes I take. If you have a big motor adjustment screw like on G&P grips, you should also definitely measure the depth on that adjustment screw when you're happy with it, so that you can then take the screw out and put thread-lock (medium-strength) on it and then get it to the exact correct position you want it in.. This saves you a lot of pain later.

[Neurotrauma]

Originally Posted by ILLusion

I think you mis-read what I wrote. I did say that too thick shims WOULD cause your gears to seize up, which is the opposite of what you're writing.

Check your shimming. If it's too tight, it can draw additional current, which could blow the fuse.

But I lost shims, I never added any additional shims and it was working fine before I took it apart, wouldnt losing shims make it looser and thus I would hear more gears moving when I fire?