[Misc] PRESS C70hc white spots on magenta

[drodas78]

Hi. I have a new c70hc installed. I'm getting this white spots only in magenta, attached are a 11"x17" sample print and 2 letter size test prints at M=255. The controller is IC-601.

Any suggestions to fix the problem?

Thank you.

[Phrag]

Re: PRESS C70hc white spots on magenta

I'm no Production expert, but if I apply my knowledge and experience of Bizhub 282's and their white spots, it's probably a dev unit.

[PeterG]

Re: PRESS C70hc white spots on magenta

Are there any spots on the Drum?

[drodas78]

Re: PRESS C70hc white spots on magenta

Are there any spots on the Drum?

Hi,

Drum is totally clean. I tough the same at first, I checked but there are no spots. Also the white spots aren't a pattern. And only appears if the area has high magenta coverage.

Problem is not solved yet. Thank you for any more help.

[monkeybum]

Re: PRESS C70hc white spots on magenta

Hi,

It's a bit difficult to make out on the attached images...... is there anything surrounding the spot? like a haze or a 'splash' type mark. Also, you say it's not a pattern so i take it the spots are different everytime? It sounds very much dev/toner related. Whats the meter reading and parts life including running time?

[drodas78]

Re: PRESS C70hc white spots on magenta

Hi,

It's a bit difficult to make out on the attached images...... is there anything surrounding the spot? like a haze or a 'splash' type mark. Also, you say it's not a pattern so i take it the spots are different everytime? It sounds very much dev/toner related. Whats the meter reading and parts life including running time?

Hi,

Nothing is surrounding the spot. And yes, the spots are different every time. The machine is new, it has 400 clicks now.

Thank you.

[monkeybum]

Re: PRESS C70hc white spots on magenta

It could be something really simple like it just needs a dam good run to get the toner flowing through ok. Have the gamma adjustments etc and tds sensor initial adjustments been done? I'm not that familiar with the hc engine but there should be a tds output test you can run, in the manual it will give you an idea of what the value should be so it will give you a good idea if it's overtones or anything like that. Also, I'd consider things like temperature and humidity in the room it's in, contamination in the dev unit from substrate etc?

[_scoekt]

Re: PRESS C70hc white spots on magenta

Defective drum? I have seen a drum that toner does not attract in small circles at high density, hence the white background showing through. Possible to swap with another drum for test?

[khaled_abosere3@yahoo.com]

Re: PRESS C70hc white spots on magenta

Check fixing unit!

[_scoekt]

Re: PRESS C70hc white spots on magenta

If AC bias on developer is too high it will result in white spots with higher density (200-255).

[drodas78]

Re: PRESS C70hc white spots on magenta

If AC bias on developer is too high it will result in white spots with higher density (200-255).

How can I check more into this? The white spots are only seen at higher density. Is there any adjustment to lower the AC bias?

[drodas78]

Re: PRESS C70hc white spots on magenta

Check fixing unit!

I think fixing unit is OK because the other 3 colors have no problem at all.

[gurko_gg]

Re: PRESS C70hc white spots on magenta

Hello
İt seemslike bad huminity envoirment.

Enter the serv mode
proc adj
Check the bias value on magenta
if value 0, enter -2
and execute gamma auto adj