Connect with us

Testing Oddball MOSFETs

Discussion in 'Datasheets, Manuals and Component Identification' started by KilgoreCemetery, Jan 9, 2018.

Scroll to continue with content
  1. KilgoreCemetery

    KilgoreCemetery

    239
    11
    Apr 12, 2017
    I really just want a second opinion on whether or not these are good. One is a P-Channel 2SJ162 and the other is an N-Channel 2SK1058. I'm using my DMM in Diode mode and the MOSFETs are out of circuit. The two things that are tripping me up the most are the built-in Zener diodes and the odd pin outs.

    J162: With the black lead on the Source pin and the red lead on the Drain pin, I'm getting zero voltage drop. Reversing the leads, gives the same result.

    K1058: Source to Drain is a 0.006 voltage drop. Reversing the leads gives the same result.

    Just based on this information, I believe they are both bad, but I've had so much difficulty in finding adequate replacements that I'm really starting to second guess myself on these. Any help/info would be greatly appreciated.
     

    Attached Files:

  2. kellys_eye

    kellys_eye

    4,275
    1,146
    Jun 25, 2010
    Seriously? Invest in one of those cheap Chinese electronic component testers. They are invaluable for simple tests, checks and basic measurement of all types of device and MOSFETs are included.

    They identify pinout, go-nogo status and basic device parameters. Just randomly connect the three test wires and it tells you which wire is connected to which lead!

    For the sake of $15 it's not worth NOT having one (or two!).

    https://www.ebay.co.uk/itm/LCD-Comp...285951&hash=item41cf5cf45f:g:8NMAAOSwRplZt4oE

    I got one and re-housed it in a decent case with perspex cover for the display and it's in almost constant use. Never failed me.

    Shorted - goosed.
     
    KilgoreCemetery likes this.
  3. duke37

    duke37

    5,364
    769
    Jan 9, 2011
    Connect the base (no gate!) to the source, the FET will then be turned off but will show a 0.6V drop in the reverse direction due to the internal diode.
    A floating base can leave the FET turned on.
     
    Last edited: Jan 9, 2018
  4. KilgoreCemetery

    KilgoreCemetery

    239
    11
    Apr 12, 2017
    @kellys_eye Wow. I normally avoid Chinese equipment, but I definitely didn't realize those things were quite that cheap or idiot-proof.

    @duke37 Thanks, I'll try that
     
  5. KilgoreCemetery

    KilgoreCemetery

    239
    11
    Apr 12, 2017
    Ok. I now have a component tester like you mentioned, but I'm still wondering if I'm reading it right or if the replacement MOSFETs I've received are just fakes, or maybe they have a different internal design. Anyway.. I've tested one of the original J162's, the first replacement, and a never-been-used, second replacement. I matched the pinout from the data sheet to the numbering system of the component tester to avoid confusion.

    Original: Diode uF 547mV C=0pF
    It also has a diode symbol between pins 2 and 3, but the arrow is pointing towards pin 2

    First Replacement: Resistor 47.5Ω between pins 1 and 3, 0.48Ω between pins 2 and 3

    Second Replacement: Resistor 21.9Ω between pins 1 and 3, 0.24Ω between pins 2 and 3

    Are any of these any good? Are the replacements even compatible with the original?
     
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,418
    2,788
    Jan 21, 2010
    Show us a picture of what appears on the tester's screen.
     
  7. KilgoreCemetery

    KilgoreCemetery

    239
    11
    Apr 12, 2017
    Original:
    20180121_135318.jpg

    First Replacement:
    20180121_135359.jpg

    Second Replacement:
    20180121_135421.jpg
     
  8. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,418
    2,788
    Jan 21, 2010
    It looks like the last 2 are thoroughly failed, effectively bring shorted out.

    The first one *might* be ok if it has a Vgs(th) higher than the tester can supply.

    What are the part numbers corresponding to images 1, 2, and 3?

    Have the parts been handled using anti static precautions?

    Have any of the parts been in circuit?

    Post a link to the exact tester you purchased.
     
  9. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,418
    2,788
    Jan 21, 2010
    Reading back, those sound like they're all 2SJ162's, P channel MOSFETs.

    3V should be enough to turn on the MOSFET, so the tester should work. Also, they have protection for the gate so it should be relatively difficult to destroy.

    Have you tried the tester on some normal transistors just to make sure it is working?
     
  10. KilgoreCemetery

    KilgoreCemetery

    239
    11
    Apr 12, 2017
    This is the tester: https://www.amazon.com/gp/product/B071Y5CHPK/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

    Those MOSFETs are all the same part numbers, J162. The first one is from series 8L1 and the other two are from series 7J3. The first two have been in circuit, but the third one has not. Also, I feel like I should emphasize the part where these have a different pinout than every other MOSFET I've come across.

    I did try a "normal" one. It's an IRFP9420. It's what I was going to use until I realized the Source and Drain pins are reversed on the J162's. Here's the readout for it:
    20180121_172429.jpg
     
  11. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,418
    2,788
    Jan 21, 2010
    Well, that is what you should see for a working mosfet.

    Don't get too concerned about the pinout. As long as you can connect them in circuit the right way, it's fine.
     
  12. KilgoreCemetery

    KilgoreCemetery

    239
    11
    Apr 12, 2017
    So, just to clarify, the original J162 came out of a Sherwood AM-7040 Receiver with a burnt out channel and I'm trying to find a compatible replacement (the one I'm testing now showed good with my multimeter). The other two are the same model number, but purchased off of ebay because I couldn't find a good replacement on digikey/mouser with the odd pinout. Am I just being duped by counterfeit parts? Are they all good/bad? Are they compatible with each other?

    I'm basically at the end of my rope with this receiver and am considering just cutting my losses at this point.
     
  13. kellys_eye

    kellys_eye

    4,275
    1,146
    Jun 25, 2010
    ISTR you actually fitted those devices before I pointed out the pin assignment was incorrect. If you actually powered up then you *****d them immediately.

    Unless you have good reason for needing identical pinouts then simply bending the leads up and cross-soldering them to the CORRECT pads (using short lengths of wire) wouldn't be a problem at all.

    I believe your replacements were suitable - other than their pinouts - so obtaining more and wiring them in correctly should sort you.
     
  14. KilgoreCemetery

    KilgoreCemetery

    239
    11
    Apr 12, 2017
    I did do a test run with some of the "normal" IRFP9420's before you pointed that out, kellys_eye, but I went back and rechecked the source voltage as well as the transistors themselves. The initial idea was to just replace all the output transistors at that point, but now I'm just trying to replace the ones that were bad from the get-go. Unfortunately, I can't seem to find any that match the characteristics of the good originals.

    At this point, I suppose it couldn't hurt to just wire in the IRFP9420's and their N-channel counterparts
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-