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[SMPS] IC: M51977 pin number 2 no voltage or frequency detected!

Discussion in 'Repairing Electronics' started by r.raslan, Nov 21, 2012.

  1. r.raslan

    r.raslan New Member

    Nov 21, 2012
    I am trying to fix switching mode power supply /SMPS/.
    There is a DC bus votage = 309 VDC.
    The MOSFET and the Triac are both functioning well (have been tested out the circuit)
    The feedback circuit (i.e photocouplers are also well function and tested out the circuit).

    The IC: M51977 which is responsible to generate PWM to drive the MOSFET has no voltage measured on its V_out pin (#2) also the frequency on this pin is zero.

    of course the IC has 12VDC power measured on its Vcc (#16) and GND(#13).

    Do you agree with me that this IC is the broken part or do you think there are other parts affecting this IC in order to generate output voltage and frequency on the V_out pin?

    Ps. attached is the datasheet of the IC: M51977

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