Bizhub C308 Power Supply Humming Noise - Fuser

[BillyCarpenter]

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.

Good stuff. I was thinking any humming noise is usually generated by an inductor or transformer.

[BillyCarpenter]

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.

By the way, what is your background? You sound like an engineer?

[engr]

@Billy, you would be correct sir. I am an aerospace engineer who happens to have dabbled in electronics for the last 30 years ~ We removed the Sony power board from this machine for inspection and found it is extremely well built. Top quality capacitors (Rubycon) and the board layout is made for serviceability. Actually the whole machine seems to be well built. We found nothing wrong with the board aside from the noise. I am going to try strapping the coils to see if I detect any change in the noise.

Do you or anyone else have access to some of these manuals that might help me further? I'm kind of flying blind right now. Service manuals and circuit diagrams would help me understand this better.

Thank you!

[BillyCarpenter]

@Billy, you would be correct sir. I am an aerospace engineer who happens to have dabbled in electronics for the last 30 years ~ We removed the Sony power board from this machine for inspection and found it is extremely well built. Top quality capacitors (Rubycon) and the board layout is made for serviceability. Actually the whole machine seems to be well built. We found nothing wrong with the board aside from the noise. I am going to try strapping the coils to see if I detect any change in the noise.

Do you or anyone else have access to some of these manuals that might help me further? I'm kind of flying blind right now. Service manuals and circuit diagrams would help me understand this better.

Thank you!

I don't work on this brand or I would be glad to send you the manual. I'm sure someone will help you out. Thanks for the education, tho.

[blackcat4866]

I'll share what we're provided ... which is to say not much. It's been over a decade since we got actual circuit breakdowns. The most you can hope for is pinouts and signal names.

[engr]

@Blackcat, thank you for that! It's at least more data than I had before.

Yeah, I'm disappointed how much of a "disposable" world we're now living in. The solution always seems to be to replace the part when it could be easily repaired if information was given. I wonder what the chances are that I could get a Minolta engineer on the phone and obtain a schematic of the board? Sometimes we get lucky.

[tsbservice]

@Blackcat, thank you for that! It's at least more data than I had before.

Yeah, I'm disappointed how much of a "disposable" world we're now living in. The solution always seems to be to replace the part when it could be easily repaired if information was given. I wonder what the chances are that I could get a Minolta engineer on the phone and obtain a schematic of the board? Sometimes we get lucky.

I agree with you. But chances are slim, I doubt even KM direct in USA have them. Maybe if some HYTEC engineer is member of this forum he could help.

[blackcat4866]

I agree with you. But chances are slim, I doubt even KM direct in USA have them. Maybe if some HYTEC engineer is member of this forum he could help.

That's a good idea! Hytec repairs the boards ... maybe they get more resources than we get.

Factory Authorized Circuit Board Repair by Hytec Dealer Services, Inc.
=^..^=

[BillyCarpenter]

That's a good idea! Hytec repairs the boards ... maybe they get more resources than we get.

Factory Authorized Circuit Board Repair by Hytec Dealer Services, Inc.
=^..^=

I'm sure they do. I've spoken with Hytec techs on the phone many times but I've never asked them for any schematics. I'm thinking they probably wouldn't release that info as there's no money in that for them. Same for Ricoh. There's just no money it it for them.


Of KM or whomever.

[copier tech]

@Blackcat, thank you for that! It's at least more data than I had before.

Yeah, I'm disappointed how much of a "disposable" world we're now living in. The solution always seems to be to replace the part when it could be easily repaired if information was given. I wonder what the chances are that I could get a Minolta engineer on the phone and obtain a schematic of the board? Sometimes we get lucky.

Its all about safety now, back in the day I would carry a soldering iron & use it most days, however not today not used it in years.

All manufactures don't want to 'allow' us to repair these boards & risk causing a fire & create a law suit!