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simonh

Blown 'fet record?

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So after killing four - yes four mosfets trying to upgrade a gun I have finally managed to get one in and run a full hi cap though the gun without blowing it.

 

A combination of the motor gears wearing through wires, shorting out when refitting the stock barrel or ver heating the fet soldering on smaller diameter wiring.

 

So I ended up with smaller wiring (rated correctly) and modifications to the lower receiver and stock barrel to make it all fit without comprising any of the wiring sleeve integrity.

 

 

So come on, fess up has anyone blown more?

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2 so far....

 

1 chewed up wires in v2 box by motor pinion

(lesson learnt, carefully route wires better now)

 

1 home made 3034 just blew up - f*ck knows but obvious short somewhere mega heatshrink now

 

So far not had a 3rd but what with the juice that goes through them - I don't take things for granted now.

 

One thing I have learnt you really can't rush cut corners thinking that will be OK on anything inside the box

I now take a hell of a lot longer putting stuff together

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I can honestly say I've never blown a 'fet. I have fitted several (mostly Gate ones - Nano in my M4, Pico in my AK - and a BTC in my SCAR, plus others in friends guns). Maybe because I used to do this kind of stuff for a living?

 

Peoples complete inability to solder doesn't seem to put them off having a go.

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"How hard can it be?"

 

ask my first psx I tried to chip, what a mess using a massive 30w red hot screwdriver tip

crap solder that was probably meant for plumber's to solder pipes, no flux and wire that was way to thick and burnt back

 

kynar, decent soldering iron, flux - piece of pi$$

 

As to gearboxes - proper planning of the wires and layout makes life easy or not so easy

 

like many things - learning by our mistakes

(still making them now and then so with that I'm still learning with every ball I drop though hopefully not so many - fingers crossed)

 

Always say a lot of stuff is like MFI or IKEA furniture - first one takes hours, second one hour

by the time you put together the 4th cabinet - 25mins I'm a pro

(no you are too tight to buy quality furniture pre-built)

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I have blown an AEG fuse but not a FET, some of the ones made by GATE have built in electronic fuses that cut the circuit if they detect a short and self reset so i have never had to replace a mosfet, G&G ones on the other hand get bloody hot but have not blownon me yet, FYI i use only 11.1v LiPos too

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"How hard can it be?"

Exactly my thoughts when I was going to swap my a Tamiya for Deans. I went down the route of "YouTube vids make it look really easy...so why not give it a go...".

Fortunately I had a wave common sence before taking out the wire cutters :-/

 

After reading on here that only LiPo really benefit from Deans - and there's not much to gain from doing it if running NiHm - my AEG is still internally stock and still working. (For now)

 

I know, I'm going to get lynched for staying NiHm - but I've never had a problem with them. And I don't have a small fortune lying around to buy a new LiPo Charger.

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1 RPS increase:

 

 

don't sound much but demonstrates how much small tamiya is choking the flow of juice

(ooh ergh missus get them juices flowing)

 

on a gun a bit more beefed up small tamiya is holding ya back even more so

(being yanks it is maybe running on higher juice to begin with but all the same stock gun stock wiring....)

 

11.1v 12c - 12c ????

 

that is a bit lame 20c to 30c is a decent punch burst rating, maybe as gun is not fetted he might be going easy

all the same when running neodym motors and thicker wires drawing more juice a mosfet is highly highly recommended

 

I know, I'm going to get lynched for staying NiHm - but I've never had a problem with them. And I don't have a small fortune lying around to buy a new LiPo Charger.

 

 

In actual fact there isn't such a massive expense as people make out if you look around....

 

Basic B3 chargers are no worse or no slower than some of the basic £12 nimah chargers

you can pick up china ones for about £3 to £5 and need a 11-18v 1.0a psu nicked from old router/modem

(though tbh don't bother getting these lame lipo chargers get mains B3 or a B6 type)

 

Better mains B3 are about £10 to £12 - bit better, some crappy clones out there to be careful if buying on fleabay

(B3's still only charge through the small balance leads so are slower but quite foolproof usually so easy to just pick up & use)

 

Then there are B6 type and B6 AC - the first B6 needs a psu 11 to 18v but min 3.0a to 5.0a psu - possible laptop psu ??

Clone B6's start about £12 upwards but advise going to get genuine B6 charger tbh not much more from hobbyking uk/eu

I have clones but have tested it and only slightly slightly undercharges but a lot quicker than a B3 type lipo charger

(a bit of manual reading is a good idea - can charge all sorts of stuff and adjust loads of settings - yeah good idea to have a read first)

 

Batteries - lipo's have the edge and are in general no more expensive - reckon cheaper than what Zero One and others would charge ya for a nimah battery.......

 

Only exception if your gun likes running on about 9.6v - inbetween 7.4v & 11.1v lipo

yes there is LiFe @ 9.9v but tbh the range is quite limited and imho the LiFe's don't offer the same raw grunt as LiPo's

So in my mind LiFe's are not really all that I first thought they would be....

A neo motor on 7.4v or if a slow motor use 11.1v (mosfet is very good idea on higher juice)

 

When you make the jump you will see for yourself I reckon

eventually nimah's tend to lose their ability to hold charge as they get old - more than lipo I'd say

 

Lipo's you don't let then run down too low 3.0v or damage to cell will occur....

7.4v - you will deffo know when she is getting low on juice @ 6.0v

11.1v - hmmm not so easy on 3 x 3.0v = 9v

but end of day get alarm or know ya gun and change lipo at lunchtime

 

the cells go up to 4.2v = 8.4v on a 7.4v - danger @ 6.0v

or 12.6v on 11.1v lipo - danger @ 9.0v

 

don't pop holes in lipo or they explode - burst into flames but just common sense stuff really

 

nimah's can be run right down without damage but often they lose their ability to hold charge for very long

or 1 out of 7 or 8 cells craps out and it just refuses to charge properly

well that is what I have found on some of my nimah's

 

Disclaimer - though I say you "can" use other psu's for these lipo chargers....

It goes without saying you need to have a tiny bit of common sense, a test meter AND know how to use these items

if you can't check/confirm voltage and polarity etc... then buy a proper psu for ya charger or buy the AC versions

 

I am not responsible if you blow $hit up coz ya too stupid to do a few checks first

not rocket science - just common f*cking sense chaps

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Tbh the soldering wasn't much of an issue once I got my eye in for it and bought a decent iron and helping hand. Had to learn some lessons on getting the wiring to sit right in the gearbox.

 

I should have just done the receiver mods after the second fet, but that meant taking it into work and I was confident that with extra heat shrinking I could get it through without nipping the wires. I still think it is technically possible, just bloody awkward.

 

Anyway taking it apart and putting back together so many times gave me the chance to correct the AOE, change the nozzle for a double o ring one, change the piston head, fit a stronger spring and re-shim the gears.

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1 fet & 1 Lipo so far, i used the low resistance silver upgrade wire that got hot in cqb, casing melted together & shorted out so that all went in the bin straight after. If I feel the wiring might pinch somewhere then a bit of heatshrink on that area to protect it along with heatshrink on trigger contact joints

 

My mate beastmode melted 1 a fet & battery cause his wires pinched, so I sorted that for him then tested it all with one of my fets. Just my SA80 needs one now but I'll wait for a while to do that

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Exactly my thoughts when I was going to swap my a Tamiya for Deans. I went down the route of "YouTube vids make it look really easy...so why not give it a go...".

Fortunately I had a wave common sence before taking out the wire cutters :-/

 

After reading on here that only LiPo really benefit from Deans - and there's not much to gain from doing it if running NiHm - my AEG is still internally stock and still working. (For now)

 

I know, I'm going to get lynched for staying NiHm - but I've never had a problem with them. And I don't have a small fortune lying around to buy a new LiPo Charger.

All my rifles used nimhs for well over a year but as they've given up over time, I've replaced them with lipos. I'm fortunate to have 2 programmable chargers from rc racing & lipos so I'm ok there

 

I even did the Lipo conversion for my Glock 18c electric pistol (which I still use from time to time)

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Tbh the soldering wasn't much of an issue once I got my eye in for it and bought a decent iron and helping hand. Had to learn some lessons on getting the wiring to sit right in the gearbox.

 

I should have just done the receiver mods after the second fet, but that meant taking it into work and I was confident that with extra heat shrinking I could get it through without nipping the wires. I still think it is technically possible, just bloody awkward.

 

Anyway taking it apart and putting back together so many times gave me the chance to correct the AOE, change the nozzle for a double o ring one, change the piston head, fit a stronger spring and re-shim the gears.

 

yes it is nice to get it right first time - but even better to persevere when things don't go according to plan

hopefully learning from mistakes is how we acquire wisdom

or

Launching the f*cking thing down the garden - yeah come very very close to that

(actually on different projects I have just lost it now n then over the years)

 

We are all still learning - I know I am

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got some new fets arriving today, got an m6 and my ICS CXP-APE to do - hopefully get these both right first time :)

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Fire-Storms ???

 

was seeing they sold neodym magnets too - but out of stock :(

all the same F-Storm fets I'm impressed with

and it takes a lot for me to say that - normally I just pull things apart - literally :)

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Yep some more of those, I really like the way they are made and each one comes in a lovely little presentation box that is totally unnecessary but makes you feel like you have bought a quality product.

 

I am also interested in the magnets, will be giving those a go when they come back in stock

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