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Diode identification help

Discussion in 'General Electronics Discussion' started by Steve Goldson, Apr 27, 2016.

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  1. Steve Goldson

    Steve Goldson

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    Apr 27, 2016
    I have a power supply that transforms 230vac to 24vdc & 5vdc. The PS has a fault on the 5v line and faults out almost immediately. When I stripped down and inspected the circuit board I found a blown diode on the 5v circuit. The diode is that badly blown I can't identify it. I have no circuit diagram and the manufacturer has been no help. Am I completely stuffed? The diode it two legged and black it has triangles at one end. Other diodes near it say DRA 60 or ORA60 on them. What does that represent? These diodes come from the same common block which appears to come from a large capacitor.

    Any help would be greatly appreciated. I'm an electrical and PLC engineer and haven't done any electronic circuit stuff since college so a little bit of a novice lol. I will add a pic but it's not very good.
     

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  2. Arouse1973

    Arouse1973 Adam

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    Dec 18, 2013
    Hi Steve welcome to E.P. I think we are going to need some better pictures sorry. A close up of the diode in good light so we can have a better look.
    Thanks
    Adam
     
  3. Steve Goldson

    Steve Goldson

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    Apr 27, 2016
    Hi Adam here is another pic of diode. It's absolutely blown with no identification left.
    I tried taking a pic of where it goes but it's hard to get a good shot as it's underneath the heat sink on the main board. I could try another pic of the board later? Thank you for the reply
     

    Attached Files:

  4. Arouse1973

    Arouse1973 Adam

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    Dec 18, 2013
    Hi Steve, it's really blurry and I cant see it. Two things, take a close up of the PCB and the other diodes when you have time and also any part numbers on the PCB and the model number of the power supply will help.
    Adam
     
  5. 73's de Edd

    73's de Edd

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    Aug 21, 2015
    Last edited by a moderator: Apr 28, 2016
    Arouse1973 likes this.
  6. Steve Goldson

    Steve Goldson

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    Apr 27, 2016
    Hi
    The board number Is
    AD1
    MSR1907C
    It's made by Fuji I've had no look locating a drawing. I've attached another pic of board. 2nd pic is of diodes marked up DRA60 but I can't get a good enough pic. I have a bore camera somewhere if I can find it I will have a go with that.
    Cheers
    Steve
     

    Attached Files:

  7. Steve Goldson

    Steve Goldson

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    Apr 27, 2016
     

    Attached Files:

  8. 73's de Edd

    73's de Edd

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    .


    Sir Steve Goldson . . . . . . .


    Basically . . . . .being 20-30-40-50 cent items . . .when I plugged in your priority specs of being a 600V unit at 1 Amp and switching speed capability of 120ns or faster.
    a . . .la . . . .

    http://www.mouser.com/Semiconductor...ectifiers/_/N-ax1mb?P=1z0yecxZ1yopdgtZ1yuoc7q


    a power supply that transforms 230vac to 24vdc & 5vdc.

    Can you fill me in on the voltage ratings of the four big caps in the foreground of post #6's photo ?
    ( Also the cap ufd value of the second cap from the left)

    Its also WIERD / CATASTROPIC that they used 85deg cap ratings in this design of circuit, possibly excepting the far right 680 or 470 ufd unit, that is probably being used as the main AC line raw DC filter .

    I am perceiving this blown diode as related to being an ancillary item of the raw DC switching circuitry.
    While the ACTUAL 24VDC and 5VDC supplies should be derived from two of the transformers located above the big heat sink and be utilizing single or dual schottky diodes in a case that is akin to the common case that is used for TO-220 transistor cases.


    73's de Edd

    .
     
  9. Steve Goldson

    Steve Goldson

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    Apr 27, 2016
    Hi,

    Sorry for the delay only just seen this message. Thank you for the help. I'm really struggling to find the exact FRD. How exact do I need to be on recovery time?

    All 4 of the caps are 420volts 680 micro f

    Thanks again
     
  10. Steve Goldson

    Steve Goldson

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    Apr 27, 2016
  11. davenn

    davenn Moderator

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    Sep 5, 2009

    probably not a problem since the I doubt the diode you originally had shown would not be capable of more than a few amps
     
  12. 73's de Edd

    73's de Edd

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    Aug 21, 2015
    Sir Steve Goldson . . . . . . .



    That's a current spec that your application will not see, so disregard.
    A 1N4937 or UF4007 diode would be fine for your replacement.


    Also I would like to have a camera view of the semis mounted on that major silver heatsink.
    or a read back.

    If neither of . . . .what look to be pristine . . . .white ceramic pigtail fuses of the AC input have blown, looks like you may just be having a "soft failure" board problem.

    I find very little info on Fuji related boards excepting one rebuilder that charges 7 arms and 4 legs for his reworks.

    What equipment is this unit used on.
    I see two green and four RED "status" indicator LED's . . .can you expound ?

    If marked . . . . . or even known . . . . what is the power consumption of the board and is it only outputting 24 VDC and 5VDC and at what amperage levels.



    73's de Edd

    .
     
    Last edited: May 4, 2016
  13. Steve Goldson

    Steve Goldson

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    Apr 27, 2016
    Hi 73's de Edd

    It is on a motorman robot. It feeds the CPU (5v) and the 24v does the I/O.

    From memory the Green LEDs are power on and source on. You close a volts free contact to get the source on. The red are fault LEDs and the one for the 5v comes on as soon as you put the source on.

    I will see if I can find out what Amps its pulling and try and get a good pic tomorrow when I'm reunited with the board
     
  14. Steve Goldson

    Steve Goldson

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    Apr 27, 2016
    An update.....
    I tried fitting the new diode and no change. I re-soldered joint thinking maybe dry and stupidly managed to short something :(
    So now source light won't come on either. I think it's time to give up as I can't fix one fault let alone two lol.
    One question before I hang my soldering iron up for good and return to playing with mains electric.....
    The diode in question on closer look doesn't seem to go to the capacitor bank. It seems to go to a whole in the common on the PCB and not connected to anything? How is this possible? I will attach a pic to see if it makes more sense. The pic is hard to make out as usual (need a better camera) but you have the common copper sink then just a circle with just PCB plastic in middle
    Cheers
    Steve failed electronics engineer :)
     

    Attached Files:

  15. 73's de Edd

    73's de Edd

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    Aug 21, 2015
    .


    Sir Steve Goldson . . . . . . .

    Alas . . . pity . . . . . on the situation now.

    Using your photo referencing and my digital enhancement, within its limits, and a blow up, to its pixelation threshold.

    We now have:

    (Un-mag to catch the additional bottom text )

    [​IMG]

    I have picked / marked up three areas of interest, with the top two being better lighted..
    This is a double sided board and for high current or reliability aspects they are using a hollow brass or tinned non ferrous rivet for feed thru, from one side of the board to the other.

    Center top, what looks to be a diode lead, is passing into that rivet , BUT there is also a large circular fillet of solder built up around that ground plane.
    Over to the top right the is a wire that passes onto that rivet and makes connection to the other side of the board.
    NOW . . . . the one in the area that I think will be relevant for you . . . will be the bottom left one . . .where you see the same connection manner being used .
    The first stupid question to now ask, is if you . . . for sure . . . installed the replacement diode in the same polarity orientation as the old one was.

    If that power supply is not now impaired enough to be blowing a fuse . . .you certainly still have a possibility of getting the unit operational again.
    Now, take DVM in hand and check out all of the units diodes .
    Place instrumentation in Diode test mode and be expecting a ~600-700 millivolts diode forward voltage read on common silicon diodes or in the ~400-500 millivolts for fast switching diodes or lastly down in the 200 mv vicinity for most of the Schottky diode family. ( OH . .make that . . . hot key . . .if you trust spell-check ! )
    I certainly hope that you find one or more bad diodes now.
    Then we can proceed to power devices.


    OOOOPS . . . . I forgot post #14's photo.

    Hmmmmmmmmmmmmmmmmm . . . . . . is that an algae cluster at the bottom of the Sargasso Sea ?


    73's de Edd


    .
     
    Last edited: May 6, 2016
  16. Steve Goldson

    Steve Goldson

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    Apr 27, 2016
    Hi 73's de Edd,

    Firstly when I realised a double sided board I had a dry joint on the diode I fitted as its in a tight space.... Sorted that, pretty sure it's the right way as a little diagram on the PCB to show direction. Diodes on testing seem with in range, but I will continue testing next week as I was called off the job.
     
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