BH-C-280, Transfer belt?

[Hansoon]

SCANX-24101514080.jpg

This BH-C-280 is having a strange effect which I cannot explain directly, but my guts are telling me perhaps Transfer Belt. The void is repeating every 96 mm. The front edge of the void is sharp on the feeding side but fuzzy on the trailing side. The void is not over the whole width of the paper, but asymmetric and concentrated a little more to the front of the machine. It's doing it on all colors but most visible with magenta. See attachment.

All developing units and all drums are over life and will be replaced soon.
Transfer Belt has 30 K
Transfer Roller 120 K

Had no time today to investigate further. Will continue beginning next week, but love to hear your suggestions.
Any ideas please?

Hans

Attached Files

[copyman]

Greetings Hans, 96mm is about the same circumference as drums. Since drums are over life I would start there. Would replace magenta drum first. If one drum is shorting it could affect other colors less.
How does just black print look? If you switch magenta with one of the other colors does bad test follow to that color?

[Hansoon]

How does just black print look?

It's doing it with all colors Frank, also with K but most visible with Magenta. What is wondering me, if HV charge loss plays a role, why is the leading edge in feeding direction of the void sharp and the trailing edge fuzzy?
I will go there coming Monday with 4 drum units and 4 developing units as well and to be sure also a transfer belt.

Hans

[copyman]

It's doing it with all colors Frank, also with K but most visible with Magenta. What is wondering me, if HV charge loss plays a role, why is the leading edge in feeding direction of the void sharp and the trailing edge fuzzy?
I will go there coming Monday with 4 drum units and 4 developing units as well and to be sure also a transfer belt.

Hans

I'm sure with all the "ammunition" you are bringing you will fix it. Let us know what fix was?

[allan]

Loosing charge will do the opposite. Could be dev bias dropping. Guess its from the front of the machine to the back. Drum is causing a short on the HV somewhere as mentioned would be my best guess. Please do let us know the outcome of the archeological dig.

[Hansoon]

Based on the distance of the voids, I'm tending now too that it has to do with drums. Puzzling me is that the void with halftone K is less, C and Y also but M massive. K drum is always in contact with the TB so that seems possible having an influence on the CMY halftones. But why is the void with K halftone much less intense, even barely visible, than with M?

Hans

[copyman]

Hi,

In your previous post you said you were going there on Monday with drums & developer units. Did you replace drums and / or dev units?

[Hansoon]

Hi,

In your previous post you said you were going there on Monday with drums & developer units. Did you replace drums and / or dev units?

No not yet. Will make/build dev units and drum units in my workshop on Saturday, which is my favorite day for this kind of work. No appointments, no telephone calls, no obligations on that day. Just me alone in my workshop with Beethoven, Mahler, Bach, or electronic synthesizer music. I love it.

Then Monday will see. I will start to replace drum units one by one and dev units one by one until the void disappears.

Hans

[allan]

Samstag, an meinem freien Tag, Bachgitarre spielen. Selbst zu meinem persönlichen vorteil arbeite ich unter der Woche zu hart, um auf Abruf zu sein. Ein Mann muss tun, was ein Mann tun muss. Wenn ich für mich selbst arbeite, würde ich wahrscheinlich dasselbe tun.

Enjoy the peace and music. I will send you some pf my friends Weird klaviermusik to listen to. I love Erik Satie.

https://drive.google.com/drive/folders/16bisZ8cbFJMyfK-Py7YAIl6zGNZa7y5y?usp=sharing

[Hansoon]

OK, went there yesterday and I replaced drum by drum beginning Y. Strangely did the void appeared now very little by using the Halftone Test mode for CMY. But much more with K. Exactly opposite to the previous findings, where M was the worst and K the much lesser.

Finally, It turned out the drum K was the culprit and after replacing halftone patterns were much better. I continued with replacing the four developing units, and prints became perfect.

Hans

[allan]

She should be good for some time to come. Thanks for the feedback.