Bizhub 350 random partial black pages

[mrwho]

We've got one of these (awful) machines (I hate them!) doing partial black pages randomly. By randomly I mean it can be working for an entire day working fine and then, all of a sudden, start doing it on a couple of pages and then back to normal.

Here's an example (sorry for the low quality):

bh350.jpg

The white lines inside the black area look like electrical noise - the fault doesn't seem mechanical at all, rather some electronical or high-voltage problem. We've started by putting in a new PCU unit first and then a new developing unit after that, but to no avail (my colleague tells me that it just started happening more often after the new developing unit, but I can see no reason for that). After that, I tried to take out the PCB under the scanner and clean the memory and Novram contacts with a pencil eraser (I could tell the difference before and after the cleaning, so they were in fact dirty), but customer tells me it keeps happening.

Any of you had this before? My gut tells me to try the HV boards next, but I'd like some opinions before ordering them.

Cheers!

[fixthecopier]

Re: Bizhub 350 random partial black pages

Sir, I do believe you are getting ready to change the laser. Actually very easy.

[RRodgers]

Re: Bizhub 350 random partial black pages

Yeah, with the electrical noise in the copy as you have pointed out I'd start by swapping the laser.

[mrwho]

Re: Bizhub 350 random partial black pages

Thank you both! I'll pass the info back to my boss. Will keep you posted!

Cheers!

[Flash]

Re: Bizhub 350 random partial black pages

If the laser was going out you would get blank copies. If the drum is scored on one end down to the core that is what is causing your problem. The collars on the developer unit are probably wore out too. Replace the drum and developer unit and reset the counters and do an F8.

[mrwho]

Re: Bizhub 350 random partial black pages

If the laser was going out you would get blank copies. If the drum is scored on one end down to the core that is what is causing your problem. The collars on the developer unit are probably wore out too. Replace the drum and developer unit and reset the counters and do an F8.

I'd normally agree with you, but as I stated, both the drum unit and developing unit are new.

Cheers!

[wseyller]

For the laser unit to cause it, it would have to output more laser beams than needed to discharge the drum in those areas.

Does this happens with printing or does it only happens when making copies? If fine when printing from internal pages or from a computer maybe the scanner is outputting this bad image to the laser.

I would try the HV unit over laser unit.

Sent from my Galaxy Nexus using Tapatalk 2

[fixthecopier]

Re: Bizhub 350 random partial black pages

If the laser was going out you would get blank copies. If the drum is scored on one end down to the core that is what is causing your problem. The collars on the developer unit are probably wore out too. Replace the drum and developer unit and reset the counters and do an F8.

It is the laser. I am not just guessing. I know this from having had this as a work order more than once. It is not completely out, it is going bad. Also in the hundreds of drums I have changed for being damaged on 1 end, none have produced electrical noise as shown in the example.

[mrwho]

Re: Bizhub 350 random partial black pages

As we're waiting for the laser to arrive, I went and replaced the HV1 and PSU with ones we had in stock from a working machine and the problem persists. Unfortunately the working machine's laser is different (the 250 and 350 have different laser units) so I can't test until the new laser arrives.

Will keep you posted!

[blackcat4866]

Re: Bizhub 350 random partial black pages

Just curious, mrwho:

Is it just copies or prints too?

I've seen similar things on the Sharp Cougar series when the Xenon exposure lamp began to light slowly or not brightly enough. There was not enough original image to identify. The give-away was when the enduser had saved a couple sets of 10 copies. Being digital the machine used a single scan to produce 10 identical images similar to yours. A charge issue would present with reasonably unique images in a set of 10 copies, maybe even a few normal images.

I had been out on this particular machine 5 times, without ever seeing the problem and was getting pretty frustrated. Without the samples it may have taken even longer to diagnose.

Do you follow my reasoning? =^..^=