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  1. Ylli

    Troubleshoot great old Kenwood home stereo power amplifier.

    The protection circuit will trip if: 1. Either the left or right speaker output offset rises above about 0.5 volts 2. An over current is detected in the output circuitry of either the left or right channel 3. There is a fault in the protection circuitry itself How deep do you want to dig...
  2. Ylli

    Korg SP-200 piano low volume

    Strange thing here is that (if I understood correctly) as the volume control was advanced, the volume would increase up to a point, and then stop increasing. That *sounds* like the output section limiting. But the output section works fine with an external input.
  3. Ylli

    Korg SP-200 piano low volume

    So with an external audio source, you get good output from the audio section. Does the volume control behave normally, i.e. properly adjusts from minimum to maximum with no flattening? While 2.77 volts is not 'centered', it is within range and will represent the DC output of the DAC. As a...
  4. Ylli

    Korg SP-200 piano low volume

    You could use a tone output program on a computer, or yes, the headphone jack of a phone or ipod type device. Durn, I forgot to attach the pictures in the previous post. You would not need to wire it as stereo, you could just feed a mono signal (or one channel of a stereo source) into both...
  5. Ylli

    Korg SP-200 piano low volume

    Do you have another signal source of 1-2 volt p-p, such as the output of a cell phone or ipod that you could use? I would suggest you disconnect the CPU cable from the output board (CN5) and inject an external signal into the indicated points. Those points should be the inputs to the volume...
  6. Ylli

    Comedy Thread

    I seldom watch these start to finish. This one I did, it was great!
  7. Ylli

    Korg SP-200 piano low volume

    IC3 pin 8 or IC4 pin 8.
  8. Ylli

    Korg SP-200 piano low volume

    Yes and no. You need to 9 volts to get Vcc/2, but would still kike to see an actual measurement of the +9 volt supply.
  9. Ylli

    Korg SP-200 piano low volume

    The only thing that could affect both channels in the way you describe has to be something common in the audio section. It sounds like you are probably getting sufficient audio out of the DAC and into the volume control but the amplifier stage after that is limiting it's output. That...
  10. Ylli

    advantage and disadvatnge of AC to DC converter circuit

    It is 12 volts (or 9 volts with the given zener) between the two output leads. But it can be as much as 230VAC between either of the output leads and a grounded object. So it you touch *either* of the output leads, that is no different than touching one of the leads on the wall outlet.
  11. Ylli

    advantage and disadvatnge of AC to DC converter circuit

    Many of the modern 'Wall Worts' do not contain a bulky conventional transformer. They incorporate a switching power supply that uses a much smaller transformer operating at a relatively high frequency, so they can provide isolation in a small space. Here is 12V 3A unit that will handle any...
  12. Ylli

    advantage and disadvatnge of AC to DC converter circuit

    pi = pi. pi is the ratio of a circles circumference to its diameter. pi = 3.1415926535..... F = Frequency in Hz. For the US line that would be 60 Hz. C = Capacitance in Farads. e-6 is a shorthand way of saying '10^-6'. Neither. Select a more appropriate and safer circuit to power the fan.
  13. Ylli

    Korg SP-200 piano low volume

    The audio section could be tested further by lifting the injecting an external signal into the high side of the volume controls, and seeing if the gain with a different source seems normal. Could inject that audio here:
  14. Ylli

    advantage and disadvatnge of AC to DC converter circuit

    Reactance of 0.1 uF capacitor at 60 Hz Xc = 1/(2piFC) = 1/(2pi*60*0.1e-6) = 26526 ohms That 10K resistor is also in series, so total source impedance: Zs = √(10,000² + 26526²) = 28348 ohms. With a 220 vac source, short circuit current will be: I = E/Z = 220/28348 = 7.76 mA Any load voltage...
  15. Ylli

    advantage and disadvatnge of AC to DC converter circuit

    This isn't going to provide enough current for anything more that the smallest of fans.
  16. Ylli

    Korg SP-200 piano low volume

    Looks like the voltages are OK. The mute signal normally would just turn the audio output on and off, but it can act as an attenuator if it is somewhere between on an off.
  17. Ylli

    advantage and disadvatnge of AC to DC converter circuit

    You would want a Class Y safety capacitor. Example: https://www.digikey.com/product-detail/en/kemet/PHE850ED6100MD18R06L2/399-5422-ND/1927367 . The output voltage is going to be almost totally dependent on the load, including the load supplied by the Zener diode. With the input capacitive...
  18. Ylli

    Can't quite figure out the function of the fourth terminal on a potentiometer.

    The loudness tap is normally not a 'Center tap', it is more commonly between 1/4 and 1/3 of the pots rotation. And then the pot is usually logarithmic which complicates the problem. Again, save the old one if at all possible.
  19. Ylli

    Korg SP-200 piano low volume

    I'd start with the assumption that the digital section is OK, and the fault is in the analog amplifiers. (that assumption may need to be revisited) So you are looking at the Output Board KIP-2052. Start by confirming the power supply voltages are all there and correct. I see + 12 volts in...
  20. Ylli

    Can't quite figure out the function of the fourth terminal on a potentiometer.

    And no, without the tap you will not be able to retain the 'Loudness' function. Unless the pot is physically damaged, it is best to clean it up and use the old one.
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