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1971 Chrysler Radio audio transistors ?

Discussion in 'Electronic Repair' started by Sparkey, Sep 4, 2012.

  1. Sparkey

    Sparkey Guest

    Hey;

    I just got this original 1971 Chrysler radio but it has distorted audio.
    ( Chrysler 3501013 Mark 07902)
    Turns out that one of the 2 output transistors is shorted.

    Both transistors have the Motorola icon and have the numbers 7239 and it looks like 7252 respectively.

    I've been trying to identify them (here's a pic)
    http://i582.photobucket.com/albums/ss262/UCN_photo/MVC-205F.jpg

    I wonder if anyone is old enough or experienced with these to help.
    Thanks in advance.

    Spark
     
  2. I'd have to believe those are date codes, Spark.

    Jonesy
     
  3. N_Cook

    N_Cook Guest


    I would find a complementary (on the assumption 2 different datecodes) pair
    of TO126, 3 or 4A, 50 V or so transistors and jury-rig, in the first
    instance.
    1972 datecodes probably
     
  4. spamtrap1888

    spamtrap1888 Guest

    This is the craziest photo I've ever seen, if you want people to ID
    the transistor. Can you take a pic that's closer to 90 degrees than to
    150? I would like to see what the three digit numbers are in the
    corner.
     
  5. whit3rd

    whit3rd Guest

    If the (working) one is not a Darlington, it's probably a complementary
    pair (one NPN, one PNP); modern equivalent-or-better would be MJE243 and MJE253;
    replace both and you can be assured the pair is truly complementary.

    It's unlikely the 1971 transistor was of any type currently produced.
     
  6. spamtrap1888

    spamtrap1888 Guest

    Guess he's wrong about it being a 1971 radio then. If anything the
    date codes would be 1970, not 1972.

    But why would they put the date code next to the logo?
    Mee too, the first few times.
    If you want a good picture of leads on a power tab package you're in
    luck.
     
  7. Guest

    Go to Digikey, they have a selector, get something with gain like 100-300, Vcex about 25, 5 amps and 50 watts Pd and you'll ne fine.

    The only thing is this is going to be a low feedback design so if the originals were germanium you need to give it more bias. In fact I am almost suretht one is shorted B-E from your symptom. Look at that driver circuit, ot might need something, likely a small resistor.

    There just ain't that much power there.

    T
     
  8. tm

    tm Guest

    I don't think anyone did.

    BTW, you would be surprised at how much it cost to make that radio. Less
    than $5 back then.

    tm
     
  9. Sparkey

    Sparkey Guest

    Thanks for all the input.

    I apologize for the pic, I know that photobucket was acting squirrely even when I was uploading this.

    I will check on those NTE 196 and 197.
    The resistors that you mention appear to be good. So far, it's only that one transistor that went out.

    Yeah, this radio came out of a "1971 Chrysler". Not surprised it good have been replaced or swapped with a newer one somewhere along the way.

    Spark...
     
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