Mp5 = wtf!?

Mr. G36! · February 24th, 2012, 16:47

Okay, this is a new one as far as I know. Never even heard of this happening before, and I honestly can't think of any reason why this should be happening.

I'm trying to fix up an MP5, originally a Broxa, but now with a G&G lower Receiver. Internals are all stock.

Before you read ahead, know this: THE BATTERY IS FULLY CHARGED, AN WILL POWER ANY OTHER GUN I HAVE!

With the lower receiver screwed properly in place, the motor gets power fine. However, once the motor is actually installed, the gun fires once and then the motor stops getting power. At first, I thought that it was just jammed, but if I remove the motor from the grip and reattach the wires, it still gets no power. If I unscrew the lower and simply remove it (without even touching anything related to the mechbox or internals within), the motor magically gets power again, I can reinstall the lower properly and the motor still gets power. And then as soon as I install the motor in the grip, one shot and it stops getting power whether it's in the grip or not. Removal and reinstallation of the lower will again allow the motor to get power.

I honestly don't understand what's happening. At first, I thought the wiring itself must be damaged, but I checked it over and looks fine, and the motor runs perfectly until it's installed, and works perfectly after the lower is removed and reinstalled.

Am I just doing or missing some weird MP5-something or other? I can't figure this out after a full week of tinkering, so here I am...

...help, please?

AngelusNex · February 24th, 2012, 16:56

try again, when it stops remove the motor and turn it by hand then check if it's getting power. Your motor might have a burnt out spot. If that turns out to be it, you just need to replace the motor.

Mr. G36! · February 24th, 2012, 17:10

I've tried that as well, but it didn't help. The only thing that seems to ALWAYS work is removing the lower receiver. And if I'm correct, the only way that that affects anything in the gun relates to the firing selector.

HKGhost · February 24th, 2012, 17:12

yup, one side of the armature could be burnt or has carbon build up which prevents power from getting to it. Take the motor apart and clean the brushes and armature.

Rusty Lugnuts · February 24th, 2012, 17:30

IMHO you need to figure out whether the issue is the motor not getting power or the motor itself. I'm not familiar with your gun, if possible could you put it together without the motor but a meter connected to the motor leads, put the battery in and when you pull the trigger in both semi and full auto... if theres no problem you should read the battery voltage ~ every time hope this helps

kalnaren · February 24th, 2012, 17:48

Make sure your trigger is reassembled correctly. I had a similar issue with my G36 once.. drove me nuts. Mechbox worked fine out of the lower.. installed, fired once, no dice. Turned out I didn't replace a spring properly.

ThunderCactus · February 24th, 2012, 18:42

Sounds like a short.
I've had similar things happen in M4s, much more common on MOSFET and SW-COMP modded guns.
The soldered trigger connections inside the mechbox are touching the mechbox shell, ending up causing a short to the MOSFET. But only shorts when the mechbox is in the lower receiver.
I've also seen bent armatures on motors do the same thing.
Try using a different motor, and closely inspecting your trigger switch and all it's contacts.

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February 24th, 2012, 16:47	#1
Mr. G36! Trader rating Join Date: Jul 2007 Location: Beautiful Thunder Bay, where dreams become nightmares!	Mp5 = wtf!? Okay, this is a new one as far as I know. Never even heard of this happening before, and I honestly can't think of any reason why this should be happening. I'm trying to fix up an MP5, originally a Broxa, but now with a G&G lower Receiver. Internals are all stock. Before you read ahead, know this: THE BATTERY IS FULLY CHARGED, AN WILL POWER ANY OTHER GUN I HAVE! With the lower receiver screwed properly in place, the motor gets power fine. However, once the motor is actually installed, the gun fires once and then the motor stops getting power. At first, I thought that it was just jammed, but if I remove the motor from the grip and reattach the wires, it still gets no power. If I unscrew the lower and simply remove it (without even touching anything related to the mechbox or internals within), the motor magically gets power again, I can reinstall the lower properly and the motor still gets power. And then as soon as I install the motor in the grip, one shot and it stops getting power whether it's in the grip or not. Removal and reinstallation of the lower will again allow the motor to get power. I honestly don't understand what's happening. At first, I thought the wiring itself must be damaged, but I checked it over and looks fine, and the motor runs perfectly until it's installed, and works perfectly after the lower is removed and reinstalled. Am I just doing or missing some weird MP5-something or other? I can't figure this out after a full week of tinkering, so here I am... ...help, please? __________________ Airsoft It's all fun and games until someone gets hurt...and then it becomes sport!

February 24th, 2012, 17:10	#3
Mr. G36! Trader rating Join Date: Jul 2007 Location: Beautiful Thunder Bay, where dreams become nightmares!	I've tried that as well, but it didn't help. The only thing that seems to ALWAYS work is removing the lower receiver. And if I'm correct, the only way that that affects anything in the gun relates to the firing selector. __________________ Airsoft It's all fun and games until someone gets hurt...and then it becomes sport!

February 24th, 2012, 17:12	#4
HKGhost Trader rating Join Date: Nov 2009 Location: Mississauga, ON	yup, one side of the armature could be burnt or has carbon build up which prevents power from getting to it. Take the motor apart and clean the brushes and armature. __________________ Please email me as I'm not on ASC too often. Custom Build \| Upgrades \| Repairs \| Maintenance Contact: ghostgunwork@gmail.com / Private Message

February 24th, 2012, 16:56	#2
AngelusNex formerly Sepulcrum Trader rating Join Date: May 2007 Location: Kingston,ON, aka Funkasia	try again, when it stops remove the motor and turn it by hand then check if it's getting power. Your motor might have a burnt out spot. If that turns out to be it, you just need to replace the motor.

February 24th, 2012, 17:30	#5
Rusty Lugnuts Fainting Goat, Dictator of Quinte West Trader rating Join Date: Nov 2011 Location: Cobourg Ontario	IMHO you need to figure out whether the issue is the motor not getting power or the motor itself. I'm not familiar with your gun, if possible could you put it together without the motor but a meter connected to the motor leads, put the battery in and when you pull the trigger in both semi and full auto... if theres no problem you should read the battery voltage ~ every time hope this helps

February 24th, 2012, 18:42	#7
ThunderCactus Not Eye Safe, Pretty Boy Maximus on the field take his picture! Trader rating Join Date: Feb 2007	Sounds like a short. I've had similar things happen in M4s, much more common on MOSFET and SW-COMP modded guns. The soldered trigger connections inside the mechbox are touching the mechbox shell, ending up causing a short to the MOSFET. But only shorts when the mechbox is in the lower receiver. I've also seen bent armatures on motors do the same thing. Try using a different motor, and closely inspecting your trigger switch and all it's contacts.

Mp5 = wtf!?

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