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  1. #11
    Service Manager 2,500+ Posts
    Bizhub C308 Power Supply Humming Noise - Fuser

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    Re: Bizhub C308 Power Supply Humming Noise - Fuser

    Quote Originally Posted by blackcat4866 View Post
    Alright, try this:
    V=IR. When V=~0, 0/R=I or ~0 amps


    P=IV. When I=~0 and V=~0, then P=~0 watts. In practice it's never 0 watts, but you get the idea.
    I suppose technically you are correct that the fuser lamp pulses on and off at 60hz. But the same is true for the ordinary light bulb. The only problem is that it does it so fast that the human eye can't see it. As far as when a fuser lamp (or light bulb) draws the most power during the AC sine wave? Well, I agree it's never zero and to explain any further would require going into RMS power measurements.

  2. #12
    Master Of The Obvious 10,000+ Posts
    Bizhub C308 Power Supply Humming Noise - Fuser

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    Re: Bizhub C308 Power Supply Humming Noise - Fuser

    Quote Originally Posted by BillyCarpenter View Post
    I suppose technically you are correct that the fuser lamp pulses on and off at 60hz. But the same is true for the ordinary light bulb. The only problem is that it does it so fast that the human eye can't see it. As far as when a fuser lamp (or light bulb) draws the most power during the AC sine wave? Well, I agree it's never zero and to explain any further would require going into RMS power measurements.
    The light bulb is constantly connected and it's intensity varies similar to that same sine wave. The fuser heater has driver circuitry to pulse ON only at the zero-cross.
    If you'd like a serious answer to your request:
    1) demonstrate that you've read the manual
    2) demonstrate that you made some attempt to fix it.
    3) if you're going to ask about jams include the jam code.
    4) if you're going to ask about an error code include the error code.
    5) You are the person onsite. Only you can make observations.

    blackcat: Master Of The Obvious =^..^=

  3. #13
    Service Manager 2,500+ Posts
    Bizhub C308 Power Supply Humming Noise - Fuser

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    Re: Bizhub C308 Power Supply Humming Noise - Fuser

    Quote Originally Posted by blackcat4866 View Post
    The light bulb is constantly connected and it's intensity varies similar to that same sine wave. The fuser heater has driver circuitry to pulse ON only at the zero-cross.

    I see said the blind man. I didn't know that. My bad.

    I haven't really studied this stuff on the newer models. That didn't used to be the case back in the day and I suppose there's a reason some engineer came up with it but at the end of the day I can't think of a good reason. I suppose maybe it helps keep the fuser at a more consistent temp. Then again, engineers sometimes just want to be different.

  4. #14
    Master Of The Obvious 10,000+ Posts
    Bizhub C308 Power Supply Humming Noise - Fuser

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    Re: Bizhub C308 Power Supply Humming Noise - Fuser

    I think the goal is to reduce energy usage and mechanical noise. It's the same reason that copiers now have 20 or more DC motors <1 amp, and turns them ON only as needed, rather than one 8 amp AC motor that runs continuously at the same speed during the whole copy process. =^..^=
    If you'd like a serious answer to your request:
    1) demonstrate that you've read the manual
    2) demonstrate that you made some attempt to fix it.
    3) if you're going to ask about jams include the jam code.
    4) if you're going to ask about an error code include the error code.
    5) You are the person onsite. Only you can make observations.

    blackcat: Master Of The Obvious =^..^=

  5. #15
    Service Manager 2,500+ Posts
    Bizhub C308 Power Supply Humming Noise - Fuser

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    Re: Bizhub C308 Power Supply Humming Noise - Fuser

    If I remember correctly, and it's been a while....

    Back in the day on the Sharp copiers the fuser circuitry was fairly simple. A triac would receive a gate signal from the fuser circuit and the lamp was either on or off and that was controlled by the thermistor. Interesting discussion. Things have changed. I should have known. lol

  6. #16
    Service Manager 2,500+ Posts
    Bizhub C308 Power Supply Humming Noise - Fuser

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    Re: Bizhub C308 Power Supply Humming Noise - Fuser

    Quote Originally Posted by blackcat4866 View Post
    I think the goal is to reduce energy usage and mechanical noise. It's the same reason that copiers now have 20 or more DC motors <1 amp, and turns them ON only as needed, rather than one 8 amp AC motor that runs continuously at the same speed during the whole copy process. =^..^=

    That's an excellent analogy. Point well taken.

  7. #17
    Master Of The Obvious 10,000+ Posts
    Bizhub C308 Power Supply Humming Noise - Fuser

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    Re: Bizhub C308 Power Supply Humming Noise - Fuser

    Correct. And we saw plenty of bad triacs. I got to learn that lesson on a Mita DC-152Z that came incorrectly wired from the factory. Essentially the heat lamp was ON all the time. The first few times we waited until the thermostat blew. The heat roller warped like a banana each time.

    This machine got parted out then reassembled several times until one day, scrutinizing the manual, I got the bold (perhaps stupid ...) idea to swap the spade terminals on the triac. Now the fifth or maybe sixth heat roller ... it warmed up normally after almost a year. =^..^=

    Sorry, now way way off topic.
    If you'd like a serious answer to your request:
    1) demonstrate that you've read the manual
    2) demonstrate that you made some attempt to fix it.
    3) if you're going to ask about jams include the jam code.
    4) if you're going to ask about an error code include the error code.
    5) You are the person onsite. Only you can make observations.

    blackcat: Master Of The Obvious =^..^=

  8. #18
    Service Manager 2,500+ Posts
    Bizhub C308 Power Supply Humming Noise - Fuser

    BillyCarpenter's Avatar
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    Re: Bizhub C308 Power Supply Humming Noise - Fuser

    Quote Originally Posted by blackcat4866 View Post
    Correct. And we saw plenty of bad triacs. I got to learn that lesson on a Mita DC-152Z that came incorrectly wired from the factory. Essentially the heat lamp was ON all the time. The first few times we waited until the thermostat blew. The heat roller warped like a banana each time.

    This machine got parted out then reassembled several times until one day, scrutinizing the manual, I got the bold (perhaps stupid ...) idea to swap the spade terminals on the triac. Now the fifth or maybe sixth heat roller ... it warmed up normally after almost a year. =^..^=

    I've seen a few fusers go into meltdown because of a shorted triac. Major fire hazard.

  9. #19
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    Re: Bizhub C308 Power Supply Humming Noise - Fuser

    Thank you both for your replies. The reason power is switched at the zero cross is to avoid burning up the triac (which is used to switch the power on/off). It's easier, and creates less heat, to switch on a load that's unloaded. Essentially the triac creates a form of Pulse Width Modulated (PWM) A/C to the inductive coil powering the resistive heater element. Technically speaking, the voltage does not alternate between +/- 60V or +/- 120V, it alternates between 120*sqrt(2) or 169.7V. We just use the Root Mean Square of the peak when we refer to AC voltage. You guys probably already know that, but I just wanted to make sure we're on the same page.

    What I think I'm hearing as far as the humming is the inductor windings physically moving. I think stabilizing those will help. It appears the triac commands a pulse to the inductor coil which then releases it's energy (DC) into the resistive fuser heating element. I don't know if the current spike is normal because I don't have any information about the power board/pcb.

    I will tinker with the heat selector value. Where can I find a service manual that tells me what each value does? Are there circuit diagrams and other technical information that would help me understand if the operation is normal? I don't have all the manuals.

    Oh, there was a comment about my lights. I have LED lights in the office. Yes, they are sensitive to line loads.

    Thank you.

  10. #20
    Service Manager 2,500+ Posts
    Bizhub C308 Power Supply Humming Noise - Fuser

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    Re: Bizhub C308 Power Supply Humming Noise - Fuser

    Quote Originally Posted by skynet View Post
    Not quite, it rises to +120volts and decends to -120volts

    Actually, it's about +170vac on the upper peak and -170vac on the lower peak if you look at it on an o-scope. On a volt meter it will read 120vac because it uses RMS value. (60v upper peak and 60v lower peak using volt meter.)



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