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Repairing Clarion MCD 360 Crossover

Discussion in 'Repairing Electronics' started by kasey, Jun 27, 2017.

  1. kasey

    kasey New Member

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    Ok so I am reparing a clarion MCD360 Crossover. The problem is that it is not powering up at all i.e. the red power led is not illuminating when the remote terminal, the batt+ terminal and the ground terminal is connected to a reliable 12volt supply.

    I obtained the service manual from online and traced the problem to the power supply stage, but I cannot seem to figure out what is the problem. Attached is the power supply stage schematic.

    I am not getting any voltage out of T1 (The step up power supply transformer). On IC2, I am also not getting anything out of pins 9 and 10. I assumed the IC was bad and replaced it, but that did not solve the problem (my bad. lol) I also replaced ZD1 because I was getting voltage before it, but nothing after. But after replacing it, I got the same readings. So now I am perplexed as to what is the problem. No caps shorting, all resistors seem to be fine. What am I missing?
     

    Attached Files:

  2. kasey

    kasey New Member

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    No help??????
     
  3. alec_t

    alec_t Well-Known Member Most Helpful Member

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    What voltages do you have on input P39-C and on pin 12 of the IC?
     
  4. dave

    Dave New Member

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  5. kasey

    kasey New Member

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    P39c is 12.2 Volts and pin 12 is 11.5volts I think. Will confirm it this evening.
     
  6. kasey

    kasey New Member

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    yes that is the approximate voltage.
     
  7. alec_t

    alec_t Well-Known Member Most Helpful Member

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    Can you list the voltages on all of the IC pins and on P39-A ?
     
  8. kasey

    kasey New Member

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    Sorry for the late response. But here are the details you asked for:

    Pin Voltage
    1 0.050 Volts
    2 2.048 Volts
    3 0.051 Volts
    4 0.042 Volts
    5 1.699 Volts
    6 3.529 Volts
    7 0.000 Volts
    8 12.17 Volts
    9 3.318 Volts
    10 3.856 Volts
    11 12.20 Volts
    12 11.35 Volts
    13 5.03 Volts
    14 5.03 Volts
    15 4.36 Volts
    16 2.048 Volts
     
  9. alec_t

    alec_t Well-Known Member Most Helpful Member

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    Is the oscillator section of the TL594 working correctly? (Check pins 5 and 5 with an oscilloscope).
     
  10. kasey

    kasey New Member

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    I do not have an oscilloscope. And I think you meant pins 5 and 6??

    Also, I replaced that IC with a new one bought from the store when I found no voltage going into T1. Could it be that the IC I bought and replaced, is defective also?
     
    Last edited: Aug 8, 2017
  11. alec_t

    alec_t Well-Known Member Most Helpful Member

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    Oops. Yes.
    A pity you don't have a 'scope. A multi-meter with a frequency-measuring range would be handy instead.
    It's always possible the replacement IC is faulty, but unlikely if bought from a reputable source.
     
  12. Les Jones

    Les Jones Well-Known Member

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    In post #9 when you say "I found no voltage going into T1." Do you mean that there was no voltage on pin 2 of T1 ? If this is the case then check for a break in the track to that pin. This is because you have about 12 volts on pins 8 and 11 which are fed from the same supply via 10 ohm resistors.

    Les.
     
  13. kasey

    kasey New Member

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    Thanks for your input Alec. I think my meter can measure frequency. What exactly should I be looking for? What is a 'good reading' when measuring the frequency on pins 5 and 6?


    Thanks for your input Les. When I said no voltage going into T1, I meant that I assumed that I would get an AC voltage going into pins 1 and 3 of the transformer (T1). I know T1 is a step up transformer and only AC can be stepped up. So no AC voltage BETWEEN pins 1 and 3.
     
  14. alec_t

    alec_t Well-Known Member Most Helpful Member

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    With the component values listed, the oscillation frequency should be about 97kHz according to my LTspice simulation.
     

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