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Mosfet Part FQP6N40CF I have Data Sheet Need To Know Why this Part keeps going — Parallax Forums

Mosfet Part FQP6N40CF I have Data Sheet Need To Know Why this Part keeps going

sam_sam_samsam_sam_sam Posts: 2,286
edited 2009-07-01 23:24 in General Discussion
I have a 175·watt mercury vapor yard light· that has a (65 watt florescent bulb that also has the ballast built in to it )

This bulb is made to replace the 175·watt mercury vapor·lamp

I changed the mosfet pair about a month ago

This is the second time·I had to replace the mosfets
The mosfets ·have shorted ·meaning that all pins have one ohm or less

The only thing that I changed was that it had· a 1.5 amp fuse and now it has a 1.5 amp·circuit breaker in it now

There are two mosfet on this board


FQP6N40CF Here is the Data Sheets for this Part
http://www.fairchildsemi.com/ds/FQ%2FFQPF6N40C.pdf

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··Thanks for any·idea.gif·that you may have and all of your time finding them smile.gif

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Sam

Post Edited (sam_sam_sam) : 7/1/2009 2:48:19 AM GMT

Comments

  • PhilldapillPhilldapill Posts: 1,283
    edited 2009-07-01 00:05
    Sam, we need more info. What are you using this for? Can you show the circuit? HOW is it going bad? More info than needed is always better than less info...
  • sam_sam_samsam_sam_sam Posts: 2,286
    edited 2009-07-01 02:25
    Philldapille
    ·
    ·Can you show the circuit?· N/A

    I would have put more info but my Internet Concetion· has been going up and down all night

    ·

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    ··Thanks for any·idea.gif·that you may have and all of your time finding them smile.gif

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    Sam

    Post Edited (sam_sam_sam) : 7/1/2009 2:45:14 AM GMT
  • $WMc%$WMc% Posts: 1,884
    edited 2009-07-01 03:10
    Sam

    It could be some high voltage spikes coming back from the built-in ballast of the new flors lamps or high heater current to fire up the new lamps?

    A little more info would help!

    _______$WMc%________

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    The Truth is out there············································ BoogerWoods, FL. USA
  • sam_sam_samsam_sam_sam Posts: 2,286
    edited 2009-07-01 03:23
    Here is a Photo of the light

    attachment.php?attachmentid=73932

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    ··Thanks for any·idea.gif·that you may have and all of your time finding them smile.gif

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    Sam

    Post Edited (sam_sam_sam) : 7/1/2009 4:16:23 AM GMT
    u843753.jpg
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  • LeonLeon Posts: 7,620
    edited 2009-07-01 11:02
    That isn't much use. Schematic?

    Leon

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    Amateur radio callsign: G1HSM
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  • sam_sam_samsam_sam_sam Posts: 2,286
    edited 2009-07-01 20:41
    Here is· the IC chip that this· also· on the· board

    This all the Info that I have on this board at this time

    If you need a Photo of the board I can do this if need be


    uba2021P

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    ··Thanks for any·idea.gif·that you may have and all of your time finding them smile.gif

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    Sam

    Post Edited (sam_sam_sam) : 7/1/2009 8:48:48 PM GMT
    pdf
    pdf
    UBA2021 Data Sheet.pdf
    96K
  • PhilldapillPhilldapill Posts: 1,283
    edited 2009-07-01 22:55
    Sam, typically, there are three main causes of failure for a MOSFET.

    1. Overheating. This can be caused by either more current than the FET can handle, or the FET not being 100% on, so the RDS_on is higher than it should be.

    2. Higher voltage spikes on the Drain-Source connections than the MOSFET(and sometimes Zener in parallel) can handle. Chances are, you have a high freq. switching circuit in there somewhere since it's a CFL.

    3. Gate voltage being exceeded. If your Gate to Source voltage exceeeds the maximum allowed in the datasheet, you can fry the gate, leaving the MOSFET half-way on all the time.

    This may be a place to start. First, check the FETs to see if they are hot when the device is running. If they never get hot, chances are, #1 isn't the problem.
  • CounterRotatingPropsCounterRotatingProps Posts: 1,132
    edited 2009-07-01 23:02
    Do you have lightning strikes near?

    I've had·nearly the same bulb literally blow up from a big discharge... and in another, the FETs were fried (Phil's points 1,2, and 3 on steriods).

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  • sam_sam_samsam_sam_sam Posts: 2,286
    edited 2009-07-01 23:24
    I want to Thank every one that·has reply-ed

    Philldapill

    I had the same though about a· over heating problem
    because the board where·one of the mosfet the board is discolored where it look like it has got hot

    3. Gate voltage being exceeded. If your Gate to Source voltage exceeds the maximum allowed in the data sheet, you can fry the gate, leaving the MOSFET half-way on all the time

    What would be a good Gate to Source voltage

    I have two boards that I have had problem with

    ·CounterRotatingProps

    One board· was where the mosfet are·shorted and one of the cap had blow-en apart there had been Thunder Strom that night
    big discharge may have done in that board

    This board I have not try-ed· to fix because the cap has just numbers and letters I have found same part # for this part yet




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    ··Thanks for any·idea.gif·that you may have and all of your time finding them smile.gif

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    Sam
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