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Kurzwil K2000 (v3) blinking leds

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  • #1

    Kurzwil K2000 (v3) blinking leds

    Have Kurzweil K2000 V3 in at moment. Came in with a 'not powering up' issue. Leds would blink 4 times and then a faint glow from the lcd (blank screen). On advice from 'elsewhere' was told it would be Caps in power supply causing this (similar to smps tv fault).
    Having swapped these out (22000uF @ 16wv, 4700uF @ 25v and 1000uF @ 25v) and powered up the leds now blink 2 times and still the screen is blank. I also replaced the AA batteries at bthe same time.
    Does anyone know what the 2 blinks are and poss repair. Tried it plugged into an amp in case the lcd was faulty - no response. Have also tried the 1,2,3 + power up that has been suggested.

    regards
    In life there are no problems, only challenges but in my present situation I may have a problem
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  • #2
    Most often there is a power supply problem which might have been made worse by replacing parts randomly by suggestion from anonymous internet advice. This is a complex difficult keyboard to repair so don't start changing parts purely on hunch. The very first thing in a K2000 that is not starting up is to test for clean power at TP20 for -5vdc, TP21 +5Vdc and regulator VR6 Pin 3 should be +5vdc
    Those are the analog supplies
    The digital supply needs to have clean +5vDC on TP16.
    If there is ripple, noise or the wrong voltage on these, it will not work. Check the supplies with a scope to make sure there is no ripple or HF noise.
    The two LED flashes indicate the battery voltage is low but on this model it can be a lot of different causes such as the 5volt reference line at TP21 being noisy or the wrong value.

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    • #3
      Thankyou for this info. I will test these points tomorrow. The keyboard was given to me to have a look at with the 'see what you can do with it' tag. It stopped working about 3 years ago and was put away in a lock up at that point. I have also emailed Kurzweil for advice but won't be holding my breath for the reply as I am still awaiting a reply for a software issue with my own pc2x which won't allow me to update the firmware.
      Regards
      Joe
      In life there are no problems, only challenges but in my present situation I may have a problem

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      • #4
        Have tested the points advised with following results:

        TP16 +5.05 vdc
        TP20 -4.93 vdc
        TP21 +4.93 vdc

        VR6 tested way off the advised result : -12.15 vdc

        It would appear that the fault lies, or at least part of the fault, lies here.

        Can you advise further please

        Thanks
        Joe
        In life there are no problems, only challenges but in my present situation I may have a problem

        Comment

        • #5
          The schematic is difficult to read. I think he meant VR5 pin 3 should be +5VDC.
          Click image for larger version Name: k2000pwr.jpg Views: 1 Size: 84.9 KB ID: 837376
          Originally posted by Enzo
          I have a sign in my shop that says, "Never think up reasons not to check something."


          ​

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          • #6
            The schematic is rough, VR6 might be VR5, pin 3 of the LM78M05 that looked like VR6 but might be VR5.

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            • #7
              Located VR5 pin 3 reading +5.05 vdc. Scoped pretty clen with very minor flutter but not random (very uniform)

              OK think that's the basics covered. Any ideas from here?

              current situation - power on - leds blink twice - backlight on lcd on - basic checks carried out, as per advice, no output/lcd display - although when connected to amp you can hear subtle changes in signal when volume slider is moved.
              Could it be that an eprom or several have actually failed causing the unit to fail?
              In life there are no problems, only challenges but in my present situation I may have a problem

              Comment

              • #8
                Located VR5 pin 3 reading +5.05 vdc. Scoped pretty clen with very minor flutter but not random (very uniform)
                have reposted this bit

                OK think that's the basics covered. Any ideas from here?

                current situation - power on - leds blink twice - backlight on lcd on - basic checks carried out, as per advice, no output/lcd display - although when connected to amp you can hear subtle changes in signal when volume slider is moved.
                Could it be that an eprom or several have actually failed causing the unit to fail?
                In life there are no problems, only challenges but in my present situation I may have a problem

                Comment

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