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Testing High Voltage Rectifiers

Discussion in 'General Electronics Discussion' started by grasshopper, Apr 23, 2013.

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  1. grasshopper

    grasshopper

    26
    0
    Mar 24, 2013
    Hi All,

    Can you please advise on the correct way to test a

    ST TH8S06FP high voltage rectifier.

    Many thanks

    grasshopper
     
  2. shrtrnd

    shrtrnd

    3,821
    519
    Jan 15, 2010
    Did you try to find the manufacturer's data sheet for it?
    Typically, the manufacturer has a test circuit for the device at the end of the data sheet.
     
  3. duke37

    duke37

    5,364
    771
    Jan 9, 2011
    I looked up the data.
    600V, 8A, 1.5V forward, 12ns

    What do you want to know, if the diode is blown, then a simple resistance measurement will do.

    If you want to know whether it complies with the data then sophitcated equipment will be needed.
     
  4. RHeTTRoNiCS

    RHeTTRoNiCS

    35
    0
    Mar 28, 2013
    Put multimeter in diode mode...check the diode in forward and reverse...In forward should read about 0.5V and in reverse should read higher....otherwise, diode might be faulty....
     
  5. grasshopper

    grasshopper

    26
    0
    Mar 24, 2013
    Data Sheets

    Hi All,

    I do have the datasheet but there is no test circuit shown. It is 8 pages long and too large to post here.

    I have tested the component with a DMM initially in circuit on board and then having removed it off board.

    It reads OL (Open Line) in both directions, suggesting a failed component?

    Before I condemn the component as failed I would like to be sure that the basic DMM test is valid for this component.

    I have seen a you tube clip that involves testing high voltage rectifier diodes using a DC power supply, a series resistor and measuring the voltage in both directions across the component. You tube being what it is, I was keen to confirm and learn the correct test approach.

    The component is from an LCD TV power supply project I am working on which is another post on the forum.

    Any help is greatly appreciated.
     
  6. grasshopper

    grasshopper

    26
    0
    Mar 24, 2013
    Data Sheet ZIP File

    Attached is a ZIP file of the data sheet for the component.
     

    Attached Files:

  7. grasshopper

    grasshopper

    26
    0
    Mar 24, 2013
  8. RHeTTRoNiCS

    RHeTTRoNiCS

    35
    0
    Mar 28, 2013
    High potential diode is faulty if dmm on diode mode read OL with both directions...
     
  9. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,496
    2,837
    Jan 21, 2010
    I haven't watched the video, but it is worth pointing out that some older "stick" rectifiers had a very high forward voltage due to them being composed of many diodes in series.

    I would find a current limited high voltage DC source to measure the voltage drop in both directions to determine if there is any diode action.

    You could start with something as simple as three or four 9V batteries in series connected to the diode via a 10k resistor.

    edit: looking at the datasheet, it's not something like that, so 0L in both directions is very bad.
     
  10. grasshopper

    grasshopper

    26
    0
    Mar 24, 2013
    Latest update

    With the DMM in diode test mode the rectifier reads OL in both directions.

    Out of curiosity I switched the DMM to measure resistance.

    This time it reads OL in one direction and 1.235Meg Ohms in the other direction.

    I seem to be getting a lesson here on using the DMM in diode mode verses resistance scales???

    What do I need to learn here guys?
     
  11. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,496
    2,837
    Jan 21, 2010
    That this diode is no more! It has ceased to be! 'E's expired and gone to meet 'is maker! 'E's a stiff! Bereft of life, 'e rests in peace! If you hadn't nailed 'im to the bench 'e'd be pushing up the daisies! 'Is semiconductor processes are now 'istory! 'E's off the twig! 'E's kicked the bucket, 'e's shuffled off 'is mortal coil, run down the curtain and joined the bleedin' choir invisible!! THIS IS AN EX-DIODE!!
     
  12. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
    1,271
    Nov 28, 2011
    If the rated forward voltage is 1.5V as you say, it may read open circuit in both directions on your multimeter, depending on how much voltage the meter applies. A better test would be a 9V battery, an LED and a series resistor e.g. 3k3. Connect like this:

    negative_probe ---------- -_9V_battery_+ ---------- anode_LED_cathode ---- resistor ----- positive_probe

    With the positive probe to the anode and the negative probe to the cathode, the LED should light. The other way round, it shouldn't.
     
  13. grasshopper

    grasshopper

    26
    0
    Mar 24, 2013
    ODE to the DIe=ODE

    Resistance is no longer low,
    The current can no longer flow,

    The power on its just no go.
    The poor component has to go

    It simply cannot switch the flow,

    A new part comes from far away,
    A fresh Diode to save the day,

    I hope my TV works some day,
    The forum;s cool it shows the way,

    We live to learn and work then play,
    My old Die=ode has had its day,

    Gone to scrap I learnt today,
    Now I'm simply blown away.........
     
  14. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,496
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    Jan 21, 2010
    I could have sworn that 1.5V was not too much to read on the diode test range.

    I just tested with a red LED and only one of three meters I pulled out could show the forward voltage on the diode test mode.

    Try what Kris suggested -- a variant of what I suggested when I thought you might have an old stick rectifier.
     
  15. duke37

    duke37

    5,364
    771
    Jan 9, 2011
    The 1.5V drop will be with 8A. I expect it will be a single diode with a drop of 0.7V at low current.

    My normal analog meter uses 3V for the resistor ranges, which would test a diode with 1.5V drop. It has the disadvantage that it will blow a small transistor on its lowest range.
     
  16. sheldonstv

    sheldonstv

    68
    0
    Jul 17, 2007
    heres a simple diode tester i use with mw high voltage diodes....but a simple check on your dvm on diode test should do as long as the meter provides enough forward voltage for the device under test....
     

    Attached Files:

  17. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,496
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    Jan 21, 2010
    That was my first thought on reading the datasheet.

    However, on a closer look at the V vs I curve for 25C, I was less certain.
     
  18. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    I guess you're not seeing too many selenium rectifiers :D
     
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