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Can I replace a 2SC1969 with a 2SC2312?

Discussion in 'CB Radio Modifications' started by Tetra, Mar 15, 2012.

  1. Tetra

    Tetra Member

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    I have a very old side mic 148 that appears to be in need of a final. I dont have a replacement 1969, but I have a few old 2312's. Can I just do a straight swap? If so, should the final bias be set to 50 mA like the stock 1969?



    Thanks.
     
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  2. unit_399

    unit_399 EL CAPO

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    Yes it will work as a straight up swap. And ... yes set the bias to 50ma like the stocker.(y)

    - 399
     
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  3. mr_fx

    mr_fx Sr. Member

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    yes and the 1307 will swap too
     
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  4. n0zna

    n0zna W9WDX Amateur Radio Club Member

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    a 1307 or a 477 will do also...73 de JW
     
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  5. AudioShockwav

    AudioShockwav Extraterrestrial Admin Staff Member

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    A word Caution
    You can replace a 1969/2312/1307 with a MRF 477, BUT the Base/Emitter/Collector pin out is not the same.
    Pins # 2 & 3 must be crossed, and insulated with a small pc of heat shrink to prevent them from shorting.
    1306/1307 driver/finals are rare as hen`s teeth to find nowadays, they have not been made for a very long time.


    73
    Jeff
     
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  6. n0zna

    n0zna W9WDX Amateur Radio Club Member

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    thats right,

    the do need crossed...been so long since i fooled with trans...i like glass,tubes...73 de jw
     
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  7. Tetra

    Tetra Member

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    Thank you all!
     
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  8. unit_399

    unit_399 EL CAPO

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    DE NADA.
     
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  9. Tetra

    Tetra Member

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    Well the original final was bad (open base-emitter junction), but the replacement 2312 didn't solve the issue. After the swap I still get no bias current on the final and the voltage at the base is still sitting about 6.1V. I have a bad feeling that I just popped the replacement final (will test it tomorrow) as something else is the root cause. One thing I did notice is that TR37 gets pretty darn hot. Does anyone know what the voltages should be on that one? Also, the 148 service manual on cbtricks seems to be relatively new (5/15/98), is this applicable to the old 148's from Taiwan?

    Thanks.
     
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  10. Robb

    Robb Yup

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    TR37 is the bias regulator. You might pull it off the chassis and see if it checks out OK first. Then, check the bias diodes too (MV1Y's - I think). Just guesses from the past.
     
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  11. Tetra

    Tetra Member

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    I did in fact blow the replacement final. I pulled TR37 and it tested ok. Turns out the culprit was C152. It was leaky and allowed DC to pass from the driver collector to the base of the final with only a 10 ohm resistor in the way. A 6V B-E voltage killed both finals I would say. Replaced the cap, the final again, set the bias and it is back in business.

    Thanks again for everyone's input!
     
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