Bizhub C350 - whistling sounds and scratched copies

[com_flyer]

Hello,

It's the first time I'm posting something on this forum. But I have used it many times to solve problems (and I found solutions!).

I have a Bizhub C350. I know, it's old and should be retired from service, but I love it since it is very reliable and works with Windows 10. But I have two problems, which I could not solve:

1. When the machine works, it makes changing whistling sounds. I did not try to chase them, since a friend of mine told me "Pierre, if it works, don't fix it". But if someone knows the machine very well and knows exactly where to search, I would give it a try.

2. And a more annoying problem: when printing A3 pages, the trailing half of the copy shows scratches. Obviously, the scratches are made by the 3 separation fingers on the transfer belt assembly. I increased the fuser speed to its maximum, so as to stretch the paper between the transfer section outlet and the fusing section intake, but it didn't solve the problem completely; scratches of different lengths are still remaining, depending on daily conditions and machine temperature. Is there a way to reduce the transfer speed or any other possibility to increase the speed difference between the transfer belt and the fuser ? I did find nothing in the service manual.

Let's hope there are still "old" techs listening, who know this machine. In Switzerland, I could find no one to continue its maintenance and had to take it over myself (with no regrets: interresting, how it works and how complex it is, to print and make copies).

Kind regards to all

[Albonline]

loop detector under fuser for large size problem. squeak good luck!

[com_flyer]

Hi Albonline

The fuser loop detector works correctly, according to the i/o check page in the tech. rep. mode. The problem seems to sit elsewhere ...

Kind regards

[Albonline]

if you know the fuser driving slow is the problem , ive only seen it once on one c350 but, the fuser itself was the cause of the slow drive. roller went mushy.

[com_flyer]

Yep, the problem is definitely the fuser speed : I have now unmounted the fuser and checked all the paper guides, finns and mechanical movement of the loop detector. There is nothing wrong, that's for sure. There is also nothing that could be adjusted.

The fuser, transfer belt and 2nd transfer roller are all brand new, so there is no worn-out part that could cause the scratches. Strangely, the problem got worse with the new parts ...

What nerves is that the machine is able to make nice A3 copies when warm. The problem occurs mainly after startup or wakeup.

Could it be a solution to modify the 2nd transfer roller speed? Isn't that a way to slow down the transfer speed, instead of increasing the fusing speed?

Thanks for your help again

[Albonline]

Yep, the problem is definitely the fuser speed : I have now unmounted the fuser and checked all the paper guides, finns and mechanical movement of the loop detector. There is nothing wrong, that's for sure. There is also nothing that could be adjusted.

The fuser, transfer belt and 2nd transfer roller are all brand new, so there is no worn-out part that could cause the scratches. Strangely, the problem got worse with the new parts ...

What nerves is that the machine is able to make nice A3 copies when warm. The problem occurs mainly after startup or wakeup.

Could it be a solution to modify the 2nd transfer roller speed? Isn't that a way to slow down the transfer speed, instead of increasing the fusing speed?

Thanks for your help again

the fuser loop sensor is supposed to take care of the speed sync between the various drive systems , did once see a color unit in that family need a clutch for the 2nd feed/ transfer roller drive, though i don't remember if it was a c350.

[Albonline]

15.3 Operation
15.3.1 Fusing Roller drive control
A. Speed change control
• Drive for the Fusing Unit is provided by the Fusing Drive Motor.
• To prevent poor fusing performance, the speed of the Fusing Drive Motor is changed in
three steps according to the type of paper used and the copy mode.
B. Speed stabilization
• To prevent double transferred image or brush effect, the difference between the fusing
speed and paper transport speed during image transfer is corrected.
• The fusing speed is made either faster or slower than the system speed.
• The two-step speed control is accomplished using the Fusing Paper Loop Control (solenoid)
and planetary gears. When the Fusing Paper Loop Control (solenoid) is deenergized,
the planetary gears rotate, which sets lower speed. When the solenoid is
energized, the planetary gears stop and the higher speed is selected.
Paper Type/Copy Mode Fusing Speed (mm/sec)
Plain paper/Monochrome 165
Plain paper/ACS or color 100
Special paper, high gloss paper 60

[Albonline]

1. The fusing speed in the beginnings is set to the higher speed, thereby forming a loop in
the paper between the 2nd Image Transfer Roller and the Fusing Roller.
2. When the length of the loop becomes small to deactivate the Fusing Paper Loop Sensor,
the fusing speed is switched to the lower level.
3. When the length of the loop becomes large to activate the Fusing Paper Loop Sensor,
the fusing speed is again switched to the higher level.
4. The sequence of these operations is repeated so that the fusing speed is automatically
changed in two steps according to the loop length. This effectively makes for the difference
between the fusing speed and paper transport speed during image transfer.


loop control c350

[com_flyer]

Hi Albonline

Thanks very much for these very interesting explanations. Again, it's more complicated than one could imagine.

On the C350, there is a clutch on the 1st transfer roller (not on the second directly). What is it for? The field service manual doesn't explain it. Can it have an effect on the fuser loop?

About the fuser speed: is there a way to monitor the fuser speed and the state of the fuser solenoid? The tech. rep. mode doesn't indicate it on the panel, only the switches and detectors. Since the solenoid is deep inside the machine, to change it would be quite tricky I guess.

Kind regards

[Albonline]

Hi Albonline

Thanks very much for these very interesting explanations. Again, it's more complicated than one could imagine.

On the C350, there is a clutch on the 1st transfer roller (not on the second directly). What is it for? The field service manual doesn't explain it. Can it have an effect on the fuser loop?

About the fuser speed: is there a way to monitor the fuser speed and the state of the fuser solenoid? The tech. rep. mode doesn't indicate it on the panel, only the switches and detectors. Since the solenoid is deep inside the machine, to change it would be quite tricky I guess.

Kind regards

like you said very old unit , haven't seen one in a few years, the clutch drives the roller, if its slipping the transfer roller would drive slow, but it seems it would be more random fault . does running a heavier stock make it worse? slipping drive parts would present themselves under the heavier load.