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Identifying and replacing diodes??

Discussion in 'Troubleshooting and Repair' started by BlueC, Aug 5, 2017.

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  1. BlueC


    Aug 5, 2017
    Good Afternoon,

    I have just started repairing Tv power boards at the component level. Identifying replacement diodes is driving me crazy. For example two that I am currently looking for are marked as SF5H9 and LT6SB5, neither of which match either the Pro-electron or Jedec coding systems. Googling doesnt help, although I did find a SF59 on an online electronics store.

    What am I missing here and how do I find the right replacement part? Caps and resistors are easy, but these diodes have me stumped. Just a note, I was also unable to find the Hatachi Power board schematic, which I thought might shed some light.

    Thank you in advance for any feedback.
  2. kellys_eye


    Jun 25, 2010
  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    There are all sorts of diodes, and all sorts of applications for diodes in which different characteristics are important.

    Unless you know a side is faulty, replacing them all willy-nilly may just result in you introducing all sorts of subtle faults.

    What are you trying to do? Are these components known to be faulty? What is their function in the circuit?
  4. 73's de Edd

    73's de Edd

    Aug 21, 2015
    Sir BlueC . . . . . .

    " Hatachi Power board "

    Soooo . . . . that information is just about as broad, useless and general model specific as " I gots this heres "Ford" . . . . that I am having trouble with.
    Just looking thru diodes . . . . no info on the cryptic LT6SB5.
    The SF5 aspect could be the larger 3A version of the SF1 and the suffix could be revevant to the voltage rating OR the packaging profile, with it being a surface mount instead of a leaded unit. Either of the units are ultra fast switching rated . . . . say maybe in the 35ns range.
    AS said . . . . .a SPECIFIC Hitachi model number of the unit is a necessity, as they just as likely could be one of a kind assigned house numbers.

    73's de Edd
  5. dorke


    Jun 20, 2015
    Welcome to EP,

    The correct way is to get the service manual of the "instrument" you are repairing.
    You should check the schematics, the PCB ,and the part list to find out the fullest info possible on the device.
    i.e. It's manufacture part number,it's function in the circuit, and the "free space" around it.
    If you can't get the original part ,you may find an exact or similar replacement ,
    or even improvise(last resort action) if you have to.

    There are free service manuals on the web(some luck needed) and there are paid ones as well.
    You can also contact the "instruments" manufacture for info(sometimes they help).
    Good luck.
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