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Roland kc-550, no output?

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  • #31
    I had a Class D output filter capacitor go up in flames.

    It went when feedback ran amuck through the PA.

    And yes, I went with a higher voltage rating too.

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    • #32
      thanks for the reply. after the caps and speaker blew i put a secondary speaker in to see what would happen and it outputted my signal but at a low distorted volume with very broken sounding dynamics. does that mean the output is fine and the caps just randomly blew for no reason (except for the fact that i was pushing the amp hard when the caps blew)?

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      • #33
        It sounds to me like you've got problems other than the Zobel network. Have you checked for DC on the output as Jazz P Bass suggested in post #29?
        "I took a photo of my ohm meter... It didn't help." Enzo 8/20/22

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        • #34
          Oscillation might cook the zobel, and could also cause weak distorted output.
          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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          • #35
            How do I find post #29?

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            • #36
              http://music-electronics-forum.com/t27953/#post380909

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              • #37
                do you mean synth occilation? sorry, im a noob. thanks for you patience. although the output is distorted and awful sounding does that fact that im getting signal mean that the output is fine and that maybe i just cooked the zobel from pushing my synth too hard?

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                • #38
                  The amp 'should' work fine without the Zobel.

                  If the output is distorted than there is another problem.

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                  • #39
                    Originally posted by Jazz P Bass View Post
                    The amp 'should' work fine without the Zobel.

                    If the output is distorted than there is another problem.
                    Let me slightly correct this: the amp should work properly ... driving a resistor load.

                    With a real world, reactive speaker, things change
                    Juan Manuel Fahey

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                    • #40
                      We have seen numerous KC-550's with blown woofers. Not the best speaker when pushed hard for a long time. Sometimes it takes out the Zobel. Check the woofer. Make sure the cone doesn't hangup at the end of its travel.
                      Drewline

                      When was the last time you did something for the first time?

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                      • #41
                        so do you think that my zobel/speaker getting blown could have simply been a result of pushing it hard for a long time? i have a brand new eminence delta lfa ready to install into my blown amp once i replace caps and resistor. the new speaker in my 2nd kc550 sounds great and seems much more efficient than the old stock speaker.

                        ps: with my speaker that blew it was actually the coil that burned out, the cone is fine.

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                        • #42
                          Sometimes the coil overheats & blows, sometimes the cone hangs up resulting in intermittant sound. We have seen the Zobel blown & the speaker seem OK because it cooled off & started moving again. We always check the travel of the cone on any KC-550 that comes in.
                          Drewline

                          When was the last time you did something for the first time?

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                          • #43
                            So I should be good to go after replacing the blown c26 and c 27 and r41 resistor and speaker?

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                            • #44
                              Make sure there is no DC present at the output before connecting a speaker.
                              Otherwise you will end up with another burnt voice coil.
                              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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                              • #45
                                thanks so much. going to test it in a minute.

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