How to find a transistor replacement

Discussion in 'General Electronics Chat' started by toozie21, Oct 4, 2012.

  1. toozie21

    Thread Starter Member

    Oct 4, 2012
    43
    1
    I am more of a digital guy, but I am trying to make a replacemnt controller for my snow maker machine I have. The controller is very simple and takes in 11.3V from the snow maker, and then spits out 11.3V when off, and a range of 1.4V - 6.6V when on depending on how hard you want the snow blower to blow (by turning a 90k pot). The circuit is simple and I basically understand it and can recreate it, EXCEPT for the transistor.

    The transistor is labeled as a C945 P228C which appears to be an old NPN transistor. I have some 2N2222 lying around and it seems comparable, but I can't quite tell. How do I know if it will be OK (some particular value I should look at?)?

    There isn't really any fast switching that needs to be done and as far as I can tell the voltage dividing is being handled by the pot, so I figure as long as the transistor can handle the voltage levels, I should be pretty close. Am I way off in this thinking?
     
  2. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    The pinouts are different on the Asian 2SC945 compared to the metal case or plastic case 2N2222. Look at their datasheets.
     
  3. toozie21

    Thread Starter Member

    Oct 4, 2012
    43
    1
    Yikes, good call on the pinout. That could have hurt me (I assumed it was standardized). Otherwise do you think they are close enough to work (I will be using protoboard, so the different pinouts will be fine)?
     
  4. MrChips

    Moderator

    Oct 2, 2009
    12,446
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    I have seen different pinouts for 2N2222. You have to be careful with this one.

    If you are sure that it is a NPN transistor, I would try substituting whatever is available but I would go with one with a higher current/wattage rating.
     
  5. toozie21

    Thread Starter Member

    Oct 4, 2012
    43
    1
    I am calling it an NPN since that is what it seems to be in random 2SC945 and C945 datasheets, but I could be wrong (or making a bad assumption).

    Is there a generic NPN that you recommend, maybe I will pick some up to have on the shelf and then I can try out for this design.
     
  6. MrChips

    Moderator

    Oct 2, 2009
    12,446
    3,362
    There are way too many transistors to call. 2SC945 is rated at 50V, 100mA.
    2N3904 is 40V, 200mA and 2N2222 is 40V, 600mA. Either should work in your application.
     
  7. t06afre

    AAC Fanatic!

    May 11, 2009
    5,939
    1,222
    As tip in such cases Google search like the ones below may give some help. It is also well inside the scope of this forum. Asking for transistor replacement. The full name of your transistor is 2sc945. But it is not uncommon to drop the first two letters
    2sc945 replacement
    2sc945 cross reference
    2sc945 equivalent
    2sc945 substitute
     
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