[Misc] Overall density is low, white spots on solid pattern - Pro 951

[Takhnamishvili]

Hello guys!

Have a density problem on BH Pro 951. When I'm trying to print 100% density, it prints approx. 70%, also there are some strange white spots on printouts. Replacing drum, performing Max density auto adj, toner density initial adj, drum set mode did not help, replacing IDC sensor did not help, replacing TCR sensor did not help (Dev. unit has only 400K prints on counter) I'm attaching photo, any suggestions will be appreciated.

Best Wishes


Untitled-1.jpg

[tsbservice]

Re: Overall density is low, white spots on solid pattern - Pro 951

On other models white spots are usually related with second transfer, I don't know this model but may give it a look.
Also you can try to Change the control of the toner density sensor to increase toner density (DipSW5-5, 6, 7).
Good luck

[Takhnamishvili]

Re: Overall density is low, white spots on solid pattern - Pro 951

On other models white spots are usually related with second transfer, I don't know this model but may give it a look.
Also you can try to Change the control of the toner density sensor to increase toner density (DipSW5-5, 6, 7).
Good luck

Thanks for your advise. I've already tried changing that dipswitches but it gave nothing. I'm sure that these white spots and low density are somehow related to each other, but can not find exact solution.

[Toxic]

Re: Overall density is low, white spots on solid pattern - Pro 951

Usually when i see this on my several bizhubs 950 it caused by weak developer and time to replace it.
Often it happened about 1 mil clicks in my case.

[ZOOTECH]

Re: Overall density is low, white spots on solid pattern - Pro 951

I've seen this symptom on Sharp models, and the cause was poor paper quality.

[blackcat4866]

Re: Overall density is low, white spots on solid pattern - Pro 951

Is there a repeating interval in the specks, on 13" X 19" paper? What direction of travel? May I assume that you are not doing the recommended maintenance as described in the manual? =^..^=

[Synaux]

Re: Overall density is low, white spots on solid pattern - Pro 951

I've seen this symptom on Sharp models, and the cause was poor paper quality.

Paper causing this? What are you using 1800's parchment? (Or perhaps laid OR maybe even felt) with a built-in option for the feed-roller/blade/IU/dev issue?

[Takhnamishvili]

Re: Overall density is low, white spots on solid pattern - Pro 951

Developer and Dev. Unit have only 400K on counter, no more. On other 951s I have not seen such problem even when developer counts 1.200K. Anyway I'm going to swap them tomorrow for troubleshooting purposes.

Symptom occurs on other papers too.

There is no repeating interval between these white spots, their location is random. Feed direction is from right to the left as you look at the photo. I'm doing maintenance, so printer is clean and also all spare parts are ok, they're not at the end of their life.

[Synaux]

Re: Overall density is low, white spots on solid pattern - Pro 951

Developer and Dev. Unit have only 400K on counter, no more. On other 951s I have not seen such problem even when developer counts 1.200K. Anyway I'm going to swap them tomorrow for troubleshooting purposes.

Symptom occurs on other papers too.

There is no repeating interval between these white spots, their location is random. Feed direction is from right to the left as you look at the photo. I'm doing maintenance, so printer is clean and also all spare parts are ok, they're not at the end of their life.

This is out of my wheelhouse, but HV board?

[allan]

Re: Overall density is low, white spots on solid pattern - Pro 951

Try switch 6 bit 7 to 1.
That will disable auto drum voltage control. Basically ignoring the DPS sensor. It would go to a preset value, option to change it would be greyed out.
If there is a massive improvement it means that the DPS the drum or the charge is wacky.
No clue whats up with your machine. Could even be environmental.

[Takhnamishvili]

Re: Overall density is low, white spots on solid pattern - Pro 951

This is out of my wheelhouse, but HV board?

I did not swap it, but I think I must try. There are two HV boards, HV1 and HV2 and I think I have to try both of them. Thank you for suggestion

[Takhnamishvili]

Re: Overall density is low, white spots on solid pattern - Pro 951

Try switch 6 bit 7 to 1.
That will disable auto drum voltage control. Basically ignoring the DPS sensor. It would go to a preset value, option to change it would be greyed out.
If there is a massive improvement it means that the DPS the drum or the charge is wacky.
No clue whats up with your machine. Could even be environmental.

Thanks for your suggestion, I will try this dipswitch and write here how it goes 😊

[allan]

Re: Overall density is low, white spots on solid pattern - Pro 951

Thanks for your suggestion, I will try this dipswitch and write here how it goes 😊

Don't dismiss the fact that it could be developer.

[Toxic]

Re: Overall density is low, white spots on solid pattern - Pro 951

I always start with basics,in this case try swap complete developing unit from another machine (if you can) and leave HV boards for the end.
But i strongly believe developer will solve this problem regardless (realively) current low part life.
I have expirience for example, developer will crash long before if machine done lot NCR paper.

[blackcat4866]

Re: Overall density is low, white spots on solid pattern - Pro 951

I'm personally leaning towards primary charge. If I had wires and grid on-hand, I would do that first. If I'd gone this far without resolution and had to order, I'd probably replace the primary charger assy. =^..^=