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Help Identifying MOSFET ?

Discussion in 'General Electronics Discussion' started by Inked, Oct 13, 2017.

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  1. Inked

    Inked

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    Oct 13, 2017
    Hi guys ;)

    I'm trying to repair a hoverboard.

    After checking the motherboard i could see that there were a few mosfet's reading low resistance.
    Lifting them up slightly revealed a few that are corroded (rusty legs) and some leaking.

    I've been to my local component supply store but they are unable to identify them.

    I have attached a picture of them and the numbers/letters written on them are:

    B070N80

    Y5163 04G


    Does anyone know what this is and where they can be bought ?
     

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  2. Chemelec

    Chemelec

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    Jul 12, 2016
    I can't find anything on that Part Number, But I would Guess it is an "N" Mosfet, rated at 70 Volts and 80 Amps.
    Seems Strange such a High power MOSFET and No Heat Sink?

    Probably a STP75NF75 would be a good replacement.

    The Y5163 04G, is Just the manufactured Date Code.

    I could send you 2 of these STP75NF75, if your prepared to pay the Mailing cost.
     
    Last edited: Oct 14, 2017
  3. Inked

    Inked

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    Oct 13, 2017

    Thanks for the reply.

    That's VERY kind of you but i need about 6 of them so ill try and buy some locally.

    That is strange if it is 70 Volts and 80 Amps but then it does have a 36 Volt battery and would be under a lot of load.


    So am i right in thinking that the volts are the max volts.

    For example i could use a 100 volt one in a 12 volt application and it would still work in the same way but i wouldn't be able to use a 70 volt one in say a 100 volt application (im just trying to educate myself here....lol).
     
  4. Alec_t

    Alec_t

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    804
    Jul 7, 2015
    Correct. It's wise to allow generous headroom for both voltage and current ratings.
     
  5. kellys_eye

    kellys_eye

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    Jun 25, 2010
    You can use a device with higher ratings for voltage AND/OR current - more is better!

    What you should take care of doing is ensuring that the Rds(on) value is in the milli-ohm region (the MOSFETS 'on resistance') as this determines the power dissipated in it. The fact that they are currently un-heatsinked means (potentially) that the existing devices are low Rds(on) already.

    Gate voltage may also be an issue for you but if you chose devices close to the suggested 70V then the gate voltage requirement 'should' be available in the existing drive circuitry.
     
  6. Inked

    Inked

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    Oct 13, 2017
    one more thing....

    When trying to find out what it was i come across MOSFET'S and TRIACs.

    What are the differences between these as they look the same?
     
  7. Chemelec

    Chemelec

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    Jul 12, 2016
    If you can get them there, OK

    It Isn't just the Supply Voltage being 12 or 36 Volts..
    It can be a High Voltage Inductive Kickback from a Motor.

    I can Easily Supply 6 or Many more.
    I would have sent 2 for free, plus Shipping cost
    But for 6, I would do it for 3 pounds plus Shipping Cost.
     
  8. Chemelec

    Chemelec

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    Jul 12, 2016
    Lots of Parts LOOK the Same, But MOSFET's AND TRIAC's are TOTALLY DIFFERENT Devices.
     
  9. kellys_eye

    kellys_eye

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    Jun 25, 2010
    No, you can't use triacs in place of MOSFETs.

    I have dozens of recycled MOSFETS that would work in that situation. Many can be found in old computer UPS devices but MOSFETS aren't expensive and ARE easily available.

    Go to a site like Farnell (UK) and use their parametric search facility where you can chose the values for voltage, current, Rds(on) etc and pick one that suits based on the information above.
     
  10. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    I think it is possible that the op has removed a heatsink which the PCB is clamped to. It explains the "face down" mounting of the devices.

    I am more concerned about the "leaking" comment. These devices have nothing to leak. If what is being seen is not heatsink compound (has this been wiped of them) then what is it, and where did it come from?
     
  11. Chemelec

    Chemelec

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    Jul 12, 2016
    Yes that also Sounded STRANGE to Me.

    Possibly a Larger OVERALL Picture of the Entire Board, might be more useful
     
  12. Inked

    Inked

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    Oct 13, 2017
    Thanks for all the replies everyone ;)

    I wasn't asking if I could use a triacs in place of mosfets, I was asking what the difference is between them.


    Yes there is a heatsink...etc but it was removed before I took that picture.

    Unfortunately I've cleaned it all up now but yes the leaking was a bit strange.

    It was a bit like when a cap blows and leaks. There was also a few rusty legs.

    The resistance I was getting was 10 on the good ones and 2 - 3 on the bad ones.


    Do you think these should be ok ?

    https://uk.rs-online.com/mobile/p/family-id/8922292/
     
  13. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    What you've cleaned up may have been the heatsink compound that is required to ensure a good thermal contact between the device and the heatsink. It is typically white with a consistency a bit like toothpaste when new, but it can dry out a bit and get firmer.
     
  14. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
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    Jan 21, 2010
    Oh, and a TRIAC is essentially like a switch you can turn on, but can't turn off again. It turns off only when power to the load is removed.

    Tries are often used with AC circuits because the nature of AC (the type that comes out of your mains socket) is that it effectively turns on and off 100 or 120 times each second. DC from a battery does not do that.
     
  15. Inked

    Inked

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    Oct 13, 2017
    Thanks ;)

    No it wasn't compound and even if it was it would have been applied to the wrong side.


    Do you think the one I linked to would be ok?
     
  16. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    In that case you need to figure out where it came from.


    Hard to say. I haven't seen the specifications of the original part, I don't even know that it's an n channel MOSFET.

    What Vgs does it operate at? (rhetorical question)
     
  17. Chemelec

    Chemelec

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    Jul 12, 2016
    MOST MOSFET's have Copper Leads and Tabs. They are Tinned but Never Seen one with RUST.
    There is usually a Silicon based Thermal Grease put on the MOSFET to help HEAT CONDUCTION between the MOSFET and the Heat Sink.
    There is NOTHING Inside the MOSFET that can LEAK.

    How were you Measuring this Resistance?

    Your MOSFETS ARE N-Channel and Yes that MOSFET is Probably OK.
    BUT I DOUBT YOUR TESTING THEM CORRECTLY.
    10 OHMS DOES NOT MAKE SENSE!
     
  18. kellys_eye

    kellys_eye

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    Jun 25, 2010
    Don't test them on a resistance range. You should have a 'diode check' range on your meter, use that.

    One of the most useful purchases I made recently was this:

    http://www.ebay.co.uk/itm/128-64-LC...639604?hash=item3af459f634:g:gdEAAOSwErFZ2H8A

    If you can get the MOSFET out and connect it to such a meter it tells you as much as you'll need to know about it - pin connections, gate voltage, capacitance etc.
     
  19. Chemelec

    Chemelec

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    Jul 12, 2016
    A Diode Test will test a MOSFET for Drain to Source.
    Should read Infinity in one direction, and around 0.5 in the other direction.
    But not the Gate function.

    And the MOSFET MUST BE REMOVED FROM THE PCB For This Test.
     
  20. Inked

    Inked

    9
    0
    Oct 13, 2017
    Thanks again everyone ;)


    I tested them by putting the multimeter on the resistance setting and then measured across the two outer legs.

    Ill but the ones i linked to and see if it fixes it.
     
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