Bizhub C308 Power Supply Humming Noise - Fuser

[engr]

Hello, I own a KM Bizhub C308. The unit was built in 2018. From what I can tell, the unit performs perfectly. However, the power supply exhibits the "humming" described by other folks on similar Bizhub printers. I've tested the electronics using clamp meters, a DMM, and a digital scope. The power is being drawn by the fuser power circuit. This section of the PSU has a triac and a series inductor coil to power the fuser heaters. The individual heater lamps are approximately 1.4 ohm and 2.5 ohm. I don't have access to any specifications, so I'm hoping they are testing okay. At those impedance levels, I see why the current is drawing so hard. I see a spike every 5 seconds to about 13A. Without the inductor, the initial current would probably be around 80A! I can understand the point of keeping the fuser hot while in ready mode, but I don't see the point of a triac if we're simply turning the fuser on/off. It's a solid state switch, but it can also throttle the heat and avoid the need to turn on/off. It would likely be easier on the fuser too.

The current draw seems excessive. The lights dim and the unit makes a disruptive humming sound that is causing problems for our users.

I have two questions. 1.) is this normal for a c308 to cycle the fuser on/off like this while in the "ready" state? 2.) what can be done to mitigate the large rush of current to the printer? Do later firmware mitigate this situation by throttling the triac a little to avoid the current spike?

[allan]

Re: Bizhub C308 Power Supply Humming Noise - Fuser

Try changing the fuser temp control mode in service. Think there are like 4 different modes.

[allan]

Re: Bizhub C308 Power Supply Humming Noise - Fuser

308temp.jpg

Ok so not modes but phase control levels.
Bad image but look for it in the manual.
Describes the issue you have, its noise thrown back from the phase control that can be changed.
Depends i guess if you are on 50 or 60Hz.

[engr]

Re: Bizhub C308 Power Supply Humming Noise - Fuser

Thank you @allan for your response. I cannot really read the image from the manual you posted and I searched the manuals I have access to for the heater modes, but can't find anything. I know exactly what you're talking about and I did try changing these in service mode. I didn't notice any difference, but I didn't really understand what each mode did. It would sure be nice if KM would explain each setting in their software.

Being on 60 hz, I suppose I my setting might be different, but the machine has always been configured for 60 hz. The noise is only part of the problem. I can probably quiet the coil by gluing the windings. More of the problem is the lights near the office dim when the printer pulls heat (every 5 sec).

[ATTACH=CONFIG]47443[/ATTACH]

Ok so not modes but phase control levels.
Bad image but look for it in the manual.
Describes the issue you have, its noise thrown back from the phase control that can be changed.
Depends i guess if you are on 50 or 60Hz.

[allan]

Re: Bizhub C308 Power Supply Humming Noise - Fuser

Thank you @allan for your response. I cannot really read the image from the manual you posted and I searched the manuals I have access to for the heater modes, but can't find anything. I know exactly what you're talking about and I did try changing these in service mode. I didn't notice any difference, but I didn't really understand what each mode did. It would sure be nice if KM would explain each setting in their software.

Being on 60 hz, I suppose I my setting might be different, but the machine has always been configured for 60 hz. The noise is only part of the problem. I can probably quiet the coil by gluing the windings. More of the problem is the lights near the office dim when the printer pulls heat (every 5 sec).

Florescent lights?

[tsbservice]

Re: Bizhub C308 Power Supply Humming Noise - Fuser

When the fluorescent light flickers you should go down the levels and when there is a noise at power source system turn up the level.
It's in service mode --> Machine --> Heater control level

[blackcat4866]

Re: Bizhub C308 Power Supply Humming Noise - Fuser

It's entirely normal for fuser heaters to turn On in pulses at 60Hz intervals (in the US).

The way I understand the theory, when the AC voltage passes through the zero volt axis (or zero-cross) the heater is pulsed on so that it draws the minimum amount of watts. Some machines (specifically Kyocera, maybe others) can identify variations in the frequency. The idea is that the heater control circuitry must be able to anticipate the next zero-cross to pulse on the heater. If the zero-cross does not happen when anticipated the MFP can draw significantly more watts. Kyoceras will trigger a zero-cross error ... meaning that the AC frequency varied too much.

All that being said, humming has been an ongoing issue with certain models. There was a Canon with particularly noisy power supplies. When I ordered a replacement sometimes the power supply was quieter, sometimes louder. Sometimes putting that same noisy power supply in a different machine made it quieter. The amount of hum never affected its ability to power the machine.

If you can live with the noise, I recommend doing nothing.
=^..^=

[BillyCarpenter]

Re: Bizhub C308 Power Supply Humming Noise - Fuser

It's entirely normal for fuser heaters to turn On in pulses at 60Hz intervals (in the US).

The way I understand the theory, when the AC voltage passes through the zero volt axis (or zero-cross) the heater is pulsed on so that it draws the minimum amount of watts. Some machines (specifically Kyocera, maybe others) can identify variations in the frequency. The idea is that the heater control circuitry must be able to anticipate the next zero-cross to pulse on the heater. If the zero-cross does not happen when anticipated the MFP can draw significantly more watts. Kyoceras will trigger a zero-cross error ... meaning that the AC frequency varied too much.

All that being said, humming has been an ongoing issue with certain models. There was a Canon with particularly noisy power supplies. When I ordered a replacement sometimes the power supply was quieter, sometimes louder. Sometimes putting that same noisy power supply in a different machine made it quieter. The amount of hum never affected its ability to power the machine.

If you can live with the noise, I recommend doing nothing.
=^..^=

That's interesting but I don't understand why 60hz crossing the 0-threshold has anything to do with anything. In the USA most things run on 120vac at 60hz. So, the Ac sine wave goes up +60vac, goes down -60vac and that's equals 120vac. And it does that 60 times per second and that = 60hz.

[blackcat4866]

Re: Bizhub C308 Power Supply Humming Noise - Fuser

That's interesting but I don't understand why 60hz crossing the 0-threshold has anything to do with anything. In the USA most things run on 120vac at 60hz. So, the Ac sine wave goes up +60vac, goes down -60vac and that's equals 120vac. And it does that 60 times per second and that = 60hz.

Alright, try this:
V=IR. When V=~0 momentary, 0/R=I or ~0 amps


P=IV. When I=~0 and V=~0, then P=~0 watts momentary. In practice it's never 0 watts, but you get the idea.

[Tricky]

Re: Bizhub C308 Power Supply Humming Noise - Fuser

So, the Ac sine wave goes up +60vac, goes down -60vac and that's equals 120vac. And it does that 60 times per second and that = 60hz.

Not quite, it rises to +120volts and decends to -120volts

[BillyCarpenter]

Re: Bizhub C308 Power Supply Humming Noise - Fuser

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.

[blackcat4866]

Re: Bizhub C308 Power Supply Humming Noise - Fuser

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.

[BillyCarpenter]

Re: Bizhub C308 Power Supply Humming Noise - Fuser

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.

[blackcat4866]

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. =^..^=

[BillyCarpenter]

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