Connect with us

Identifying blown transistors

Discussion in 'Troubleshooting and Repair' started by Twiki, Mar 25, 2017.

Scroll to continue with content
  1. Twiki

    Twiki

    3
    0
    Mar 25, 2017
    Aloha !
    My new DSLR flash made a pop after 6 consecutive shots. Guess it was a bit too fast for Q3 & Q4.
    R15 (1k) and R16 (100k) have joined the party, and are out of order as well.
    Can anyone try and guess what transistors should I try and replace them with ?
    These are tssop8 packaged, and the only remaining hint is a charred '25' print on the package.
    Seems to me like they are not part of the high voltage generator circuit, but are switches of the discharge one.
    Thanks for your time !
     

    Attached Files:

  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,505
    2,849
    Jan 21, 2010
    Before you go too far, is your unit under warranty?

    Do you have access to another unit that's not dead? Has anyone done a treasurer and shown this in detail?
     
  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,505
    2,849
    Jan 21, 2010
    The good news is that they look like single MOSFETs.

    What were you doing? Did you connect a high voltage source to allow you to recharge the caps quickly?

    Are you sure the 100k resistor is fried? It's a high value and they don't normally get damaged. However, if the gate is now connected to the drain (which presumably has 300V or so on it), then the failure could be an indication that the 300V has found its way into the low voltage circuitry. If that's the case, the damage could be widespread.
     
  4. Twiki

    Twiki

    3
    0
    Mar 25, 2017
    No warranty. Even If there was a message coming out from the anonymous seller: "sure, send it over !", buying a new one from eBay for 20USD would be a far better choice.

    The 100k is out. Might have been by the blast.

    So plan B failed... and now A is the only option: get a new unit, check the MOSFET type, order a strip of 50 for 99 Cents, and solder a few as piggy-backs to share the load.

    Thanks.
     
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,505
    2,849
    Jan 21, 2010
    Oh ok, so this it from a flash FOR a DSLR, not the flash IN a DSLR.

    That may mean there's less damage (I.E. the thing that failed is cheaper. Did your DSLR survive unscathed? The hot shoe can be pretty intolerant of high voltages.

    Is it a name brand flash, or a cheap noname thing?
     
  6. Twiki

    Twiki

    3
    0
    Mar 25, 2017
    Just a $20 unit. Your time and mine mumbling about it already costs more.
     
  7. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,505
    2,849
    Jan 21, 2010
    My time is free to you. :)
     
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

-