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Why am I not getting 37V on a 37V line?

Discussion in 'Troubleshooting and Repair' started by leeadamaa, Sep 26, 2012.

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  1. leeadamaa


    Aug 6, 2012
    To start off here is the diagram


    On the 37 Volt line leading out and into the tape deck we only obtain 31.33V of power now we replaced all the capacitors with new ones and we tested the resistors out of the circuit and we wanted to know if it was possible that a resistor gave a faulty reading and read that it had gave us the proper Ohms but could be damaged inside........the main problem occuring is with the entire deck....there is a safety stop sensor that allows the tape to stop when it reaches the end of rewinding or FF and the sensor only works after we turn the system on and off several times repeadtly........

  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    Is the 31.33V measures with the load attached or not?

    If the load is attached, try removing it. Perhaps it is trying to draw too much power and the power supply is being loaded down.

    Are all rails affected, or just one?
  3. leeadamaa


    Aug 6, 2012
    the voltage is measured with the load on and the transformer has been tested to be 100% functional and only the 37v rail is affected the rest are okay and measure to the appropriate voltage
  4. davenn

    davenn Moderator

    Sep 5, 2009
    ok so 37 V no load
    its an unregulated rail so its going to drop a few volts under load anyway maybe ~ 3 - 4Volts

    As steve said you need to consider what that load is .... where does the 37V rail go ?check for shorted/low resistance components in that area

  5. duke37


    Jan 9, 2011
    24.5*sqr(2)=34.6 so you would expect about 33.5 out, unloaded. The figures are not consistent.

    To get closer than this you need to consider actual mains voltage.
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    Good point Duke37. Maybe it's a misprint. Maybe 31V is expected?

    edit: measure the voltage on the collector and emitter of Q905.
    Last edited: Sep 27, 2012
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