12v dc output power supply

Discussion in 'Electronics Repair' started by Austarlie, Oct 12, 2017.

  1. Austarlie

    Austarlie

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    i tried repairing this old nippon america dc supply, circuit board no. AQF7 820712-yo reporo. I changed these parts,2n3055 and replacet d313 with d330. I removed a tiny resistor behind colors br,black,third color burnt and silver,on the cicuit board from the internet there is a brown capicator same place the resistor was.I need the no. or value to replace?
     
    Austarlie, Oct 12, 2017
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  2. Austarlie

    73's de Edd

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    Sir Austarlie . . . . .

    With no tech info on the unit . . . . obviously its being a low thru mid power linear regulator circuit . . . . if using a 3055 and the 313/330 being its driver.

    If the resistor was a 10 ohm it could do a good burn . . . . if being a 100 ohm it could discolor and scorch.
    As it is . . . we really need good close up photos of both sides of the board to see and evaluate design and see what you really have there.


    73's de Edd
     
    73's de Edd, Oct 12, 2017
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  3. Austarlie

    Austarlie

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    73,s de edd,
    thanks for your answer.on the internet i found the circuit board ,but the thing is there is a brown capacitor instead of a resistor which i removed from the board.If i get the number i will use it instead.The circuit board both front and back on the internet is aqf7 820712 do not forget the space after aqf7.you will find it under circuito regularor. I am no tech, 63 and usually learning from others on the net. I built an entire solar system from off the net and without any experience. hey one more thing just call me austarlie.
     
    Austarlie, Oct 12, 2017
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  4. Austarlie

    73's de Edd

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    Sir Austarlie . . . . .

    I'm holding off on visual posting of a board and parts layout pending some on hands research made by you, for some confirmations.
    The boards comp and foil sides views are just being temp hosted . . . . . until all parts are identified.

    Looks like you have yourself a circa 1974-76 power unit here.

    Was that photo of your unit? . . . and the YO Reparo guys were of no help . . . asi, parace que dicen, que no pueden a reparlo para usted .

    In ancient times they made smaller wirewound resistors overclad in glossy Brown or Green enameled coating, which might resemble a capacitor to the unitiated.
    Any chance that is what might be currently installed in the unit in place of that smoked unit ?
    Check out and see if it measures resistance and if so, how much .

    HOW THIS UNIT . . . .
    Flip, flops and flies . . . considering its flippers flip and floppers flop . . . . otherwise it just can't fly

    Bottom right corner has ~ ? ~ 24VAC coming in on its bottom and top terminals referenced to a common separate center tap shared connection as the BLACK wire from the transformer.
    The two 1N540X diodes are alternatively providing a continous stream of + node rectified DC to the + terminal of the main filter cap which is retaining the high unregulated raw DC voltage to be reduced down to a chosen regulated DC voltage (12 ? ).

    Your questionable areas burnt resistor seems to be within a sub supply that feeds the regulating circuitry.
    Take note that at the botom right AC input of the power transformer input that there is a dedicated foil path that samples that lower voltage and carries it via a foil path up to the single end pad that is connected to the photo of the 1N400x series rectifier diode it then travels down to a dual pad that accepts its other lead and your BURNT resistors photo.
    This is the start of a secondary supply which has the half wave rectifier diode and then the series voltage dropping / curent limiting / sometimes fusible resistor that you now have burnt .

    Now the best that your Green on Green layout will let me somewhat questionably make out, is the path that I have overlaid in BLUE. That leads down to a BLUE mylar cap.
    Conduction thru that cap would present no significant power consumption to be able to burn that resistor.
    ( Unless the cap has dead shorted out )
    HOWEVER . . . if there is being a foil path in the strip that I have made in RED . . . that would then complete a path to a logical preregulator zener diode (in Blue).
    IF that Zener diode were to short out, there would be a short to the ground plane above, accounting for that burnt, series in line resistor .

    PARTICULARLY check out that BLUE path to see if any other connections of parts are being made into it.
    On the photos below. . . . .I need fill ins on all of the bottom queries . . . to then amend the photo correctly of some of its missing info.

    INTERIM BOARD PICS . . . . . ( Makee left clickee-clickee and it go mo' BIGGIE- BIGGIE ! )

    https://s1.postimg.org/2dbrhvw9al/Nippon_Power_Supply.png




    73's de Edd

    .
     
    Last edited: Oct 14, 2017
    73's de Edd, Oct 14, 2017
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