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Aug 24, 2019, 12:16 PM
anti-wind activist
thrashaero's Avatar
Thread OP
Help!

Trying to replace ESC mosfet chip


OK so this ESC fried a mosfet.
It is a Turnigy Sentry 40A. I took off the heatshrink and revealed which mosfet it was, as you can see in the picture it is the bottom left.
I hope to replace it. But I'm not sure on where to get the specific mosfet.
I know it is a 7832Z by International Rectifier as are all of the mosfets on the board, but there are 2 distinct sets.
The problem is getting the specific P718H U1W0 type that are on the left 2 columns in the green box, of which 1 is fried.
The other 2 columns in the blue box are P643H M4Z9 type.
I can easily find plenty of 7832Z's on ebay, aliexpress etc.
But I don't know where I can specify the other two sets of alphanumeric codes to make sure I'm getting the right one.
I get no results in search engines when I put P718H and U1W0, or either one by itself

I would really like to just spend pocket change and a little solder work for a mosfet and have it working again (was a great ESC, I think I just had it installed upside down, didn't realize it's heatsink was mounted on the bottom in the way I had it on the aircraft) than to spend another $30 on a new esc.
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Aug 24, 2019, 02:35 PM
Grumpy old git.. Who me?
JetPlaneFlyer's Avatar
Personally for $30 I’d just get another ESC. I’m all for repairing stuff but at that price point just get a new one or pick up something cheap second hand.
Aug 24, 2019, 02:56 PM
Heligamist
BrokeDad's Avatar
I agree with JPF. You might as well invest in a new/used ESC. You never know if another IC is hurt and will fail soon too. It's not worth risking the crash damage cost. Now if it was a super expensive high amp ESC fixing it might be an option.
Aug 24, 2019, 05:58 PM
¯\_(ツ)_/¯
Dave778's Avatar
Quote:
Originally Posted by thrashaero
OK so this ESC fried a mosfet.
It is a Turnigy Sentry 40A. I took off the heatshrink and revealed which mosfet it was, as you can see in the picture it is the bottom left.
I hope to replace it. But I'm not sure on where to get the specific mosfet.
I know it is a 7832Z by International Rectifier as are all of the mosfets on the board, but there are 2 distinct sets.
The problem is getting the specific P718H U1W0 type that are on the left 2 columns in the green box, of which 1 is fried.
The other 2 columns in the blue box are P643H M4Z9 type.

The other codes are just site and date of manufacture, so it shouldn't matter too much. It looks like you can get 10 on Ebay for $2.89 + $2 shipping, so I think it is worth a try if you are inclined. You may have to replace more than one fet if it is damaged, and hope the CPU, etc is fine. They probably select the fets codes to try to match parallel Ron, but it may not make that much difference. Good luck!
Last edited by Dave778; Aug 24, 2019 at 06:05 PM.
Aug 24, 2019, 06:40 PM
anti-wind activist
thrashaero's Avatar
Thread OP
yeah I can get 20 for $5.26.
I can understand for others if they dont have the solder skill/time. But looks simple enough. I don't really have the money to piss on a new esc and just hate replacing entire units without at least trying to fix the core problem.

I think the overheat came from gunning throttle on a rather hot day. the esc was also entirely covered in heatshrink, so the little heat plate that was on the mosfets didn't really have air, plus it was mounted upside down since i didn't know which side was supposed to be up. I'm going to leave the heatshrink off and put an actual heatsink with fins on to prevent the same problem happening again.
Aug 24, 2019, 07:25 PM
Registered User
Steve_'s Avatar
From what I understand, ESC's run cooler at higher throttle settings. (Not sure what gunning it means)
Anyway, valid points from everyone.

It would be a sad day if you replaced it and the one next to it failed 2 minutes into the first flight.

That said, I've spent $100 of my time to fix $10 stuff. It's an addiction, I swear.
Last edited by Steve_; Aug 24, 2019 at 07:51 PM.
Aug 24, 2019, 08:32 PM
¯\_(ツ)_/¯
Dave778's Avatar
I would heave my still smoking $30 ESC into the garbage before I even thought about it.
Aug 25, 2019, 10:26 PM
Registered User
fixing small electronics is fun and rewarding provided they work fully after the old burnt thing on the pc board episode or two repair goes well. Sure go ahead and try to fix it, I have two cc becs on which the lipo burned the first inline part, voltage egulator, shame to toss $50 down the drain, because I accidentally hooked them up backwards, and the same on a car esc (Traxxus or whatever they are called).

Soldering those tiny circuits can be challenging however unless you've got some patience and practice.

Esc's don't like partial throttle because they are being switched on and off by the timing, and they heat up as a result of not completely turning on and off, sort of a brown out condition at all times.

This is a beautiful article that will explain the esc in detail, valuable info, http://modelaviation.com/inside-esc ,
Aug 26, 2019, 03:40 AM
Registered User
Atomic Skull's Avatar
Quote:
Originally Posted by icanflyheli

Soldering those tiny circuits can be challenging however unless you've got some patience and practice.
A loupe and a magnifying visor will really help with this. And also some Kester 186.
Aug 26, 2019, 07:55 AM
Registered User
yeah, I check all my micro solders with a jewelers loupe to make sure no solder has crossed to another point (crashed Tarot zyx with broken pin connection for one).

I saw one guy soldering circuits, monolithic capacitors, on a pc board and kept wiping on a gel cleaner, that must be the Kester 186 you're talking about, soldering with help of a magnifying glass of course.

Many years ago I worked for a small electronics manufacturer and a woman in a separate room was busy laying down micro components by hand and magnifying glass, the big one that's bench mounted, otherwise your eyes would be strained. I crafted a model at close range with micro detail for 100hrs over the span of two weeks some years ago and it became difficult to focus long range for a couple of weeks after.
Aug 26, 2019, 03:42 PM
anti-wind activist
thrashaero's Avatar
Thread OP
About a week ago my wireless headphones charge port (micro usb socket) broke off....managed to get it resoldered ok and works thankfully.
My desolder stuff is kind of lame, got the sucker bulb (which has a really blunt tip and doesn't get in very close easily) and the wick braid stuff which can also be a PITA. I'd really like a vacuum pump with heated tip like I had at one company I worked at about 8 years ago.
They also had an old lady with a fancy setup involving a magnified camera on an arm she could move around, which fed video to a screen so it was easy to look at.

Thanks for that video denis747, I'll see about getting some of that desolder alloy. Looks useful.

I know that some damages to electronics are invisible...which I hate, lost a pretty good motherboard thanks to who knows what, just doesn't even POST out of nowhere.

Hopefully the fet is all that really needs replacing but I won't be surprised if it isn't.
Aug 26, 2019, 06:04 PM
Registered User
Atomic Skull's Avatar
lead free solder has made modern electronics less reliable. Lead suppresses tin whisker growth which can create shorts out of nowhere for no apparent reason. That's why NASA requires a min. lead content in all solders used in spaceflight rated electronics.
Aug 26, 2019, 07:49 PM
☆ OVERDISCHARGE MASTER ☆
Flying Pitcher's Avatar
Quote:
Originally Posted by Atomic Skull
...Lead suppresses tin whisker growth which can create shorts out of nowhere for no apparent reason.
Did nt know, thank you. I only thought poor workability due to higher melting temps was the main issue of lead free solder.
Aug 26, 2019, 07:53 PM
rc user
pdooley's Avatar
SODDERING


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