Looking for Cross-reference for Motorola M9639 transistor?

Discussion in 'General Electronics Chat' started by Johnnyb60, Mar 21, 2015.

  1. Johnnyb60

    Thread Starter Member

    Sep 6, 2013
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    Having trouble finding a replacement transistor for a 14VDC power supply. The numbers are 185, M9639, MEX, 8532 and a photo below.

    [​IMG]

    Would appreciate it if someone could point me in the right direction.
     
  2. bertus

    Administrator

    Apr 5, 2008
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  3. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
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    That's a Motorola in-house 'ID' --- While, ostensibly, there is no exact generic equivalent, please consider the following...

    The closest generic cross = 2N3772
    Note: Although many sources cite the 2N3773 as an acceptable cross, unless you are well versed with your application's parameters, I strongly advise against it - inasmuch as the 2n3773's Ic (Max) figure ~ 1/2 that of the M9639! --- You may rest assured that the 2N3772 will 'fit the bill' in nearly all cases... :)

    FWIW A reasonable after-market sub = NTE181

    In general the device's 'on-label' App is high power audio amplification.. (Common off-label applications include Royer power oscillators, linear EMF regulators, high current switching, etc...)

    Best regards
    HP
     
    Last edited: Mar 21, 2015
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  4. Johnnyb60

    Thread Starter Member

    Sep 6, 2013
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    Thanks, well I guess I'll keep looking.
     
  5. Hypatia's Protege

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    Mar 1, 2015
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    At risk of sounding the shill, I'm bound to say you could just order an NTE-181:)

    In case my post (above) was unclear please note

    2n3772 ~ NTE181 = Good MATCH

    2n3773 (notice the '3' in the rightmost digit of the 'ID') = Dubious, unrecommended substitute

    Best regards
    HP
     
    Last edited: Mar 21, 2015
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  6. ian field

    Distinguished Member

    Oct 27, 2012
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    A firm I worked for that made high power ultrasonic generators used a house coded transistor that was equivalent to the 3772.

    A quick google finds that the 3771 is the highest current in that family - the 3773 is only a tiny bit better than a 3055 but a fair bit better for breakdown voltage.

    [/QUOTE]
     
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  7. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    It might be that the original part is way overkill for the application, but was what was in the manufacturer's inventory.

    Another approach is to tell us the requirements of the power supply and reverse-engineer the device selection. For example, a 14 VDC output linear power supply probably has less than 30 Vpeak into the pass transistor. If you take the rated output of the supply times 1.5 or 2.0, that should be a safe estimate of the current rating needed. The last thing is the gain, and I seriously doubt that it needs to be much above 20 at max current because the 2N3055 influenced generations of designers. BTW, is this the only pass device or are there more than one in parallel?

    ak
     
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  8. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
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    A further caveat:

    Please! Please!! Please!!! beware of counterfeits!!! Buy only from reputable distributors (e.g. Mouser, Digikey, Newark and their ilk) *PLEASE* don't even think about Ebay! My "tuition", in this regard, was $20K+ :rolleyes:

    Best regards
    HP
     
    Last edited: Mar 21, 2015
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  9. Johnnyb60

    Thread Starter Member

    Sep 6, 2013
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    There are two I posted a thread earlier about my 14v power supply was putting out 24VDC and determined that I had a bad pass transistor. I've been searching for a week and can't find one. I even started to wonder if maybe I had the wrong numbers, because there was nothing available.

    This is the original thread http://forum.allaboutcircuits.com/threads/14-vdc-power-supply-putting-out-24-vdc.108329/
     
  10. Johnnyb60

    Thread Starter Member

    Sep 6, 2013
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    LOL well eBay was my next move and unless i find something it might be my only hope.
     
  11. Hypatia's Protege

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    Mar 1, 2015
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    Again, as stated in post #5 (q.v), you may buy the NTE-181 Directly from New Tone Electronics:
    http://www.ntepartsdirect.com

    Piece price = $9.77 (USD) / No minimum order --- You can't beat that!:)

    Best regards
    HP
     
    Last edited: Mar 21, 2015
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  12. Johnnyb60

    Thread Starter Member

    Sep 6, 2013
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    Thank you I missed that some how. I was just getting overwhelmed over all the information and how it all fit together. Anyway I just placed my order ntepartsdirect.com, thanks again.
     
  13. MaxHeadRoom

    Expert

    Jul 18, 2013
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    NTE can be handy, but they average 3x the original part price.
    I only use in a dire emergency.
    Max.
     
  14. Johnnyb60

    Thread Starter Member

    Sep 6, 2013
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    Well I just didn't know of anybody else that had it although I wasn't looking for a NTE-181 at the time. Oh well it cost me $30 for two with shipping. Anyway I'm just glad its ordered. :)
     
  15. ian field

    Distinguished Member

    Oct 27, 2012
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    Bit like Maplin in the UK - similar price ratio.

    They do components, kits and manufactured items - but I have to be even more desperate to also travel all the way to the next nearest town.

    Ordering from somewhere like Farnell is not only a lot cheaper - but Maplin *ALLWAYS* screw up postal orders. On one occasion I bought 10 each from a range of E24 resistors, one of the values was out of stock so they agreed to take the payment and forward those items from the warehouse - typically, they sent the wrong value - when I returned the pack of 10 resistors with a letter explaining it, they sent bacl only one resistor - still the same wrong value.

    The same happened, only much worse with a large order of turned pin DIL sockets, it took well over a month of exchanged e-mails to finally get the right quantity of the right parts - that was the last time I ever used Maplin.
     
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