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Aug 24, 2019, 12:19 PM
anti-wind activist
thrashaero's Avatar
Thread OP
Help!

Trying to replace ESC burnt 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, 12:46 PM
An itch?. Scratch build.
eflightray's Avatar
You could check with the DIY Electronics forum, they have designed and built ESCs in there ---

https://www.rcgroups.com/diy-electronics-199/

.
Aug 24, 2019, 03:37 PM
Registered User
vollrathd'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.
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.
FYI, do you have any idea on why that MosFet overheated? Like perhaps running the ESC at to high of a current value? The problem is, if that MosFet shorted out, it may have damaged the other MosFets in the ESC in the process.
Aug 24, 2019, 06:36 PM
anti-wind activist
thrashaero's Avatar
Thread OP
Yes, whole esc was covered in heatshrink, no exposed heatsink, so I had it mounted upside down and was flying on a rather hot day. Also the internal 'heatsink' was just a plate on some silicone heat pad. Maybe that's common but looks rather lame to me.
I'm going to leave heatshrink off and put an actual heatsink with fins on it and hopefully it will cool off better.
Aug 25, 2019, 03:55 AM
jofro
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.
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.
Put it in the bin mate! Next time, remove the heatshrink and add to mosfets larger alloy heat sink plate, with the use of heat transfer paste, secure it with the tape or cable tights to keep it exposed for better air flow over it. Easy fix.
Aug 25, 2019, 06:48 AM
anti-wind activist
thrashaero's Avatar
Thread OP
Quote:
Originally Posted by jofro
Put it in the bin mate! Next time, remove the heatshrink and add to mosfets larger alloy heat sink plate, with the use of heat transfer paste, secure it with the tape or cable tights to keep it exposed for better air flow over it. Easy fix.
Nope. Unless damage seems majority or not worth the effort, I don't throw stuff away. This seems rather acute and simple. But i know that looks can be deceiving, so we'll see.

Anyway I do already plan to be trying it without the heatshrink and a larger heatsink with actual fins on it attached with paste.
Aug 25, 2019, 08:52 AM
An itch?. Scratch build.
eflightray's Avatar
Have you tried de-soldering and re-soldering surface mount components ?, it's very easy to damage the board and tracks without a suitable soldering iron.

.
Aug 25, 2019, 10:27 AM
anti-wind activist
thrashaero's Avatar
Thread OP
Quote:
Originally Posted by eflightray
Have you tried de-soldering and re-soldering surface mount components ?, it's very easy to damage the board and tracks without a suitable soldering iron.

.
Yes. while small I've done it before with a micro usb port. I know on these fets the source pins go together and the drain pins go together, i must get the ground pin separate. I've already desoldered the burnt fet and cleaned up the pads.
Aug 25, 2019, 10:58 AM
Registered User
I would first try just replacing that one and see if the ESC works again.
Aug 25, 2019, 11:21 AM
Registered User
You only have to match the part number. The other numbers are batch and date codes.

I usually shop for components at mouser.com or digikey.com. Digikey might be better since they'll do USPS first class for a couple dollars and you can specify that on checkout. Mouser will do first class if you ask them, but they'll default to priority mail at like eight dollars and don't have a first class option on checkout.

Anyway good luck with it, probably good chance the other FETs are okay, hopefully. Use a temperature controlled iron set around 650F and lots of rosin flux. A regular 25W pencil will get too hot and possibly damage the transistor. Use 60/40 or 63/37 tin/lead rosin core solder. Avoid the lead free stuff as it requires more heat and is harder to use.
Last edited by Krager; Aug 25, 2019 at 11:31 AM.
Aug 25, 2019, 12:40 PM
An itch?. Scratch build.
eflightray's Avatar
Quote:
Originally Posted by thrashaero
Yes. while small I've done it before with a micro usb port. I know on these fets the source pins go together and the drain pins go together, i must get the ground pin separate. I've already desoldered the burnt fet and cleaned up the pads.
As the fets will probably be in parallel, If you can get the burnt one out and the board cleaned, you may be able to test the ESC before fitting a new fet. It will have reduced current capacity but should show if it still works.

.
Sep 10, 2019, 10:56 PM
anti-wind activist
thrashaero's Avatar
Thread OP
Alright well I got the new fets in.
I soldered a new one in the burnt position first of course. But then I connected battery and burnt that one too.
Thinking I maybe used too much heat while soldering, I removed that one and put another in again and burnt that one too right as I connected the battery.
So I figured screw it I need to replace them all anyway, so I did that.

I didn't have much confidence it would work since I thought i probably overheat the chips with an iron I don't know the temp of, but I powered it up and it works fine. Used programming card with no problems. Motor spins fine. Yay so far.
Sep 10, 2019, 11:46 PM
Registered User
vollrathd's Avatar
Quote:
Originally Posted by thrashaero
Alright well I got the new fets in.
I soldered a new one in the burnt position first of course. But then I connected battery and burnt that one too.
Thinking I maybe used too much heat while soldering, I removed that one and put another in again and burnt that one too right as I connected the battery.
So I figured screw it I need to replace them all anyway, so I did that.

I didn't have much confidence it would work since I thought i probably overheat the chips with an iron I don't know the temp of, but I powered it up and it works fine. Used programming card with no problems. Motor spins fine. Yay so far.
For other readers of this thread, one can always remove the prop and place a small fast blowing fuse in line with the battery while testing an unknown condition in an ESC. Proper size would be a fuse slightly more than the no load current pulled by the motor. And, use the 1/4 by 1 1/4 inch instrument fuse size, not those tiny millimeter sizes. Those small fuses may not be able to clear DC battery currents.

Don't quickly wind up the motor with the in line fuse, high startup currents could blow the fuse anyhow.
Sep 11, 2019, 12:37 AM
H-1
H-1
Registered User
H-1's Avatar
I think you will find when a fet blows that more than fets may be damaged.
Sep 11, 2019, 12:46 AM
H-1
H-1
Registered User
H-1's Avatar
I think you will find when a fet blows that more than fets may be damaged.


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