Help identifying component

Discussion in 'General Electronics Chat' started by ZackTheBruce, Jul 21, 2014.

  1. ZackTheBruce

    Thread Starter New Member

    Jul 21, 2014
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    Trying to repair a Spirent Communications power supply board that is missing this component.


    The only markings are a wierd X followed by T13 and then below BKBW.

    Any help would be greatly appreciated. Thanks!
     
  2. shteii01

    AAC Fanatic!

    Feb 19, 2010
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    It is marked RV1 on pcb.
     
  3. ZackTheBruce

    Thread Starter New Member

    Jul 21, 2014
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    I don't have the schematics for this board so I have no idea what's supposed to go into that location.
     
    Last edited: Jul 21, 2014
  4. to3metalcan

    Member

    Jul 20, 2014
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    RV is, I think, SMT code for a varistor? Someone correct me if I'm wrong. Varistors are usually used to prevent current surges.
     
  5. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    I have not seen that part before but it is likely to be a MOV.

    Photos showing both sides of the board might help becuase we could see what it is conencted to. There looks to be power diodes and a power resistor very close so this is possibly a MOV to clamp an incoming PSU rail?
     
  6. to3metalcan

    Member

    Jul 20, 2014
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    If you don't know the specs of the Metal Oxide Varistor, you can probably safely hazard a guess...

    ...is the board fused, at all?
     
  7. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    Looks like its a Cicada Semiconductor, they got bought out by Vitesse in 2004.
     
  8. ZackTheBruce

    Thread Starter New Member

    Jul 21, 2014
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    back of board.
     
  9. ZackTheBruce

    Thread Starter New Member

    Jul 21, 2014
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    Whoops! actual attached photo of the back of the board.

    Also idk about RV being a designation for a varistor as RV2 and RV3 both have capacitors in that location.
     
  10. ian field

    Distinguished Member

    Oct 27, 2012
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    My best guess would be a polyfuse - a PTC thermistor that is heated by the current flowing through it - at a certain temperature it hits the knee-curve and the resistance rises rapidly limiting the current into the load.

    In effect; a self resetting fuse, if you remove the overload it cools down and resumes normal conductivity.
     
  11. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    Time to trace out the circuit and draw a schematic. :)
     
  12. to3metalcan

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    Jul 20, 2014
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    Agreed. Can't really help anymore without some context!
     
  13. ian field

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    Oct 27, 2012
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    He'll send you the board shortly - maybe you have a better X-ray machine.
     
  14. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    It's not Cicada, their logo has sine waves, not triangles sections. This is a transient protection device of some kind. Probably a varistor because of the V in the reference designator, but I've seen tranzorbs and Polyswitch use that package. I recognize the logo but can't place it. Check with Vishay and Bourns.

    ak
     
  15. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    I do. It's between my ears, finely tuned from 30 years of repairing electronics with no schematics. I can see right through things. ;)

    Being a large suppression device next to power rectifiers it should be on power rails and easy enough to trace, even if it requires touching a multimeter probe here and there. :) (For the people who can't see through things).
     
  16. ian field

    Distinguished Member

    Oct 27, 2012
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    My guess is still a polyfuse (PTC thermistor) - I've seen a few of them used instead of consumable fuses on USB ports.

    Dead easy to check - find a board with one on it and heat it with the tip of an iron, if the resistance increases its a polyfuse. A surge suppressor won't have much resistance change till it gets *REALLY* hot.
     
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