Circuit explanation needed please.

Discussion in 'General Electronics Chat' started by TapOut64, Mar 17, 2011.

  1. TapOut64

    Thread Starter New Member

    Mar 17, 2011
    2
    0
    I had my electronics training back in 1984 and I seem to of forgotten more than I remember. In the following circuit, how is the +11V perm produced starting from U4 working to the left?[​IMG]

    Any help greatly appreciated.
     
  2. billbehen

    Active Member

    May 10, 2006
    39
    1
    U4 flip-flops, u6 inverters boost level, xfmr blocked by C58, diodes rectifiy signal (smoothed by e'lytic,) r41 prevents core wandering, turns ratio set to put out +11volts. Maybe indicator maybe small amount of DC for something on another board:)
     
  3. TapOut64

    Thread Starter New Member

    Mar 17, 2011
    2
    0
    OK, don't laugh. So the output of U4 are pulses that trick the transformer into thinking it's seeing AC?
     
  4. Adjuster

    Late Member

    Dec 26, 2010
    2,147
    302
    The transformer is not being "tricked". The square-wave output from U6A U6B effectively is an alternating voltage, just not a sinusoidal one. The use of transformers to couple square or pulse waveforms is not all that unusual.

    Whatever else the +11V may be used for, it feeds the input LED of an opto-coupler in what seems like some kind of start-up circuit.
    If -PWR ON is joined to GND, the 11V will drive the input of OP1, so that Q12 will turn on, powering up +15VS and so the PWR ON LED, and in turn U7, and so +5V.

    What is this circuit - some kind of remote control?
     
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