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  1. Ylli

    Scratching My Head w/ Crown CDi 4000

    The +30V_CNTL originates at TP31. After the unit is running, it is supplemented by a rectified signal from the transformer (D26, C196). With power off (and all the caps discharged) measure the resistance between TP31 and V_BULKRTN.
  2. Ylli

    Scratching My Head w/ Crown CDi 4000

    If you are seeing +0.6 volts at TR31, there could be a short on the +30V_CTRL bus.
  3. Ylli

    Query about the recharging of a lead acid battery

    If that is all I had, I'd just add a 10 ohm resistor in series with the charger output to limit the current, and connect it up. When the battery voltage stabilizes, give it a couple more hours and you should have at least 85% back in the battery.
  4. Ylli

    No sound from turntable

    See this thread. https://audiokarma.org/forums/index.php?threads/need-help-identifying-a-magnavox-500-solid-state-amp-receiver.825763/
  5. Ylli

    Inductor Question

    The inductor, along with the MOSFET likely for an oscillator driving the 'impeller'. Really curious as to how power is coupled to that impeller - Any pictures of the back of the board or o the cavity of the pump after the board is removed?
  6. Ylli

    I have question marks about my power supply circuit anyone can help?

    V1 is the 220 VAC 50 Hz source? The voltages in LTSpice are Peak voltages, if you are connected to the 220 VAC line, the peak voltage will be 311 Vac. Why are you concerned about the frequency response between V1 and the primary of the transformer? The only thing going through that path is 50...
  7. Ylli

    Siren circuit

    Note that anything you do to make it louder will increse the stress on the transistors. Don't have time now to do an anaysis... Even as you reduce the value of the 100 ohm series resistor, speaker current is still going to be limited by the 220 ohm collector resistors. Try reducing those...
  8. Ylli

    Need help in converting a 12VDC 16.5A PSU to +-17.5VDC 2A PSU

    If he could find up-converters that have isolated outputs, he could just connect the outputs in series aiding and ground the center tap. On the above configuration, the lower converter would need to handle 4 amps.
  9. Ylli

    Analog signal amplifier with OpAmp, Transistor or Darlington Pair?

    DIdn't disappear, its just over on ETO. :)
  10. Ylli

    Marantz PM6004 amplifier cutting out at low volume

    Glad it is working well for you. I would not recommend sockets as those can cause more problems than they solve. The new relays should last many years.
  11. Ylli

    Resistor inside an inductor.

    It does, but perhaps a better way to look at it... Since this network is in series with the outputs, at DC the coil is effectively a short circuit and the output amplifier just sees the impedance of the speaker and it's feed line. At ultrasonic frequencies, where parasitic oscillations are...
  12. Ylli

    Resistor inside an inductor.

    Yes, have done it myself may times.
  13. Ylli

    Resistor inside an inductor.

    Typical output audio amp output stage.
  14. Ylli

    Resistor inside an inductor.

    Parasitic suppression. Any high frequency parasitic oscillations drop across the inductor and are dissipated by the resistor.
  15. Ylli

    Marantz PM6004 amplifier cutting out at low volume

    Not sure what relay you are referring to here. S7503 turns the headphones on and off. Yes. Without the unit in front of me, that's hard to say, most likely not as the 'board' doesn't need to be heatsinked. If you take something apart where thermal paste is used, it is best to clean off the...
  16. Ylli

    Marantz PM6004 amplifier cutting out at low volume

    Yes, they appear to be for switching between Speaker 'A' and 'B'. As long as you are not pushing things, I don't think the 6 ohm speakers would be the cause - speaker relay failure/intermittants are actually quite common.
  17. Ylli

    Marantz PM6004 amplifier cutting out at low volume

    S7501 for the left channel and S7502 for the right channel would be the likely culprits. They are Fujitsju FTR-F4AK012T. You could try, but I don't think you will have much luck cleaning them. One source would be...
  18. Ylli

    Marantz PM6004 amplifier cutting out at low volume

    Sounds exactly like a relay problem. And that is actually quite common. Try this... when it is acting up at low volume, tap on the relay with the handle of a screwdriver and see if the audio comes back. If it does it is definitly the relay.
  19. Ylli

    Why are these two circuits equivalent?

    What would make the base voltage different? Note that in the second circuit, both voltage sources are labeled "Vcc". Since they are labeled the same, we generally assume that the Voltage of Vcc = Voltage of Vcc.
  20. Ylli

    Why are these two circuits equivalent?

    On the first circuit, what is the voltage at the top of R2? What is the voltage at the top of Rc? On the second circuit, what is the voltage at the top of R2? What is the voltage at the top of Rc? Is there any difference?
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