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MSX 84V mosfet blown. Options?


mrelwood

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4 minutes ago, mrelwood said:

 

I know I’m in a minority with my attitude to fix everything and passable repair skills regarding electronics. If there was a shop next door with MSX motors for a few hundred bills, I’d have been hard pressed to buy one as well. But while the 16S is now a decent ride (after the second battery repair), I want the MSX up and running as soon as in any way possible.

I replaced all hall sensor wires, no point in mixing new and old.

I assumed you were talking about replacing the hall sensors, which is next-level repair work.

When my hall sensor wires melted into my motor wires I first replace the control board, but like you, discovered that the wheel was still broken. My hall sensor(s) were fried. So then I had to replace the motor.

People have tried to replace the hall sensors. Some failed and some were successful.

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Nope. Most times wheel can be turned off fine, but as soon as the tire moved or is moved more than 2 inches, ”bip bip, bip bip”...

Thinking about what happened though makes it sound quite obvious:

The high current heated and burned through the motor wires, which also damaged the hall sensor wires, making a short. So the sensitive sensors got a nice 70 some volts on their butts.

Next step is to disassemble the motor again, this time taking out the hall sensors as well to check the part number. Buy, (wait?,) replace, retry.

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3 hours ago, mrelwood said:

Nope. Most times wheel can be turned off fine, but as soon as the tire moved or is moved more than 2 inches, ”bip bip, bip bip”...

Thinking about what happened though makes it sound quite obvious:

The high current heated and burned through the motor wires, which also damaged the hall sensor wires, making a short. So the sensitive sensors got a nice 70 some volts on their butts.

Next step is to disassemble the motor again, this time taking out the hall sensors as well to check the part number. Buy, (wait?,) replace, retry.

There are threads in the Forum on how to replace hall sensors. It's quite the operation and it's very important to get the correct type of sensor. @Rehab1, you tried this, right?

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I'v done this yesterday i replace all hall sensors in Inmotion V5F+ its not so complicated but there is some things that will help. I didnt assembey motor yet and i wil try to make some photos to show how to do it.

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1 hour ago, evil696 said:

I'v done this yesterday i replace all hall sensors in Inmotion V5F+ its not so complicated but there is some things that will help. I didnt assembey motor yet and i wil try to make some photos to show how to do it.

I measured the hall sensors, and one of them is indeed busted. Others’ output switches between 0 and 3V when rotating the wheel, while one gives out 3V constantly.

Photos on removing and fixing the new ones in place might be very helpful, thanks! The next step after removal is of course to source the replacements, as fast as possible.

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43 minutes ago, mrelwood said:

I need an 18” spare wheel.

OMG!! Marty, is this how it starts?!

I feel the same. When I buy my next hot new wheel, I will not sell the 18XL. During my two weeks of down time I regretted selling my V10F. One just needs several wheels. The failure rate of wheels is too high for such an addictive hobby. 

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OK lets star, you need 4 longer screws with a diameter same as cover screws.

i think you can handle it

in my motor i replace all hall sensors you need to replace only one

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Edited by evil696
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Thanks, @evil696. I was able to center the stator with just the original screws, but that is a clever tip! I will use that the next time.

The issue will be in how to get out the original sensors. Any tips for that?

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3 hours ago, mrelwood said:

Didn’t long for being smart at that moment... Honestly, that was the first time  I would’ve wanted to get blasted in 11 or such years of not drinking.

The 16S felt as such a punishment at first, but now that the battery is fixed, it’s really not that bad of a wheel. It is tiny though... I need an 18” spare wheel.

OMG!! Marty, is this how it starts?!

:D Yes indeed

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3 hours ago, UniVehje said:

I feel the same. When I buy my next hot new wheel, I will not sell the 18XL. During my two weeks of down time I regretted selling my V10F. One just needs several wheels. The failure rate of wheels is too high for such an addictive hobby. 

One should never be without at least two backups :)

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33 minutes ago, mrelwood said:

Thanks, @evil696. I was able to center the stator with just the original screws, but that is a clever tip! I will use that the next time.

The issue will be in how to get out the original sensors. Any tips for that?

I would be very interested in seeing any pictures of your motor and the hall sensor & motor cabling. Just to be able to access the quality/fragility of the interior wiring.

Any observations that you may have too. I always feel that the hall sensors are a weak point, but then again they never seem to fail by themselves.

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As you see on my picture when rotor is pulled out from magnets, hall sensor is visible and in my motor side with description is also visible, just remove glue and you should be able to read description if not you must take out hall sensor what is not so easy. I get one sensor without brake him and all other i destroyed :)

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Marty hall sensors doesnt fail by themselves but reason can be water or like in Mrelwood case broken mosfet that is shotcuted on all pins also logical pin is shortcuted with V+ so if fuse doesnt blow realy fast voltage goes from battery to logical mosfert pin to MCU and at finish to hall.

 

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43 minutes ago, evil696 said:

As you see on my picture when rotor is pulled out from magnets, hall sensor is visible and in my motor side with description is also visible, just remove glue

Ah, I was hoping that I wouldn’t have to separate the rotor. That definitely adds to the challenge. Sigh... Now I really see the usefulness of the long bolts!

 

34 minutes ago, evil696 said:

in Mrelwood case broken mosfet that is shotcuted on all pins also logical pin is shortcuted with V+ so if fuse doesnt blow realy fast voltage goes from battery to logical mosfert pin to MCU and at finish to hall.

To be precise, the hall sensor cables hadn’t shorted to eachother, but one of the main motor cables had shorted on a hall sensor cable. So it was a direct ~75V hit on one of the hall sensors.

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If you'll be thinking about selling this broken mainboard let me know i never repair MSX and it will be huge experience to measure this motherboard.

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I think I’ll keep the toasted mainboard as a desperate spare, just in case.

If you have good tips for removing the rotor, I’m all ears. The long bolts allowed enough sideways movement for the magnets to grab anyway.

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10 hours ago, evil696 said:

Marty hall sensors doesnt fail by themselves but reason can be water or like in Mrelwood case broken mosfet that is shotcuted on all pins also logical pin is shortcuted with V+ so if fuse doesnt blow realy fast voltage goes from battery to logical mosfert pin to MCU and at finish to hall.

 

Every component can fail, but yes, I know that most likely the hall sensor won't fail. But my question to @mrelwood (pictures, etc.) is more about the quality of the wiring and connections to the hall sensors. If those are crappy the the hall sensor system (sensors plus cabling) can fail, resulting in a faceplant.

My hall sensor failure and @mrelwood's failure was due to the motor cable getting so hot that it melted into the tiny hall sensor cable, resulting it ~80-volts going to the sensor.

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