7085 sometimes with light copies

[mrwho]

Hello there, guys and girls.

I've got a Konica 7085, which is a great machine but has a problem and its solution is eluding me.

The machine can be working fine, with perfectly good copies when, all of a sudden (from one copy to the other) it will start throwing out light copies (almost white). It will then proceed that way until the operator cycles the power with a long pause in between (turning it off one day and turning it on the day after, for example).

Some details:
- Sometimes cycling the power from one day to the other wouldn't be enough - it could still be giving light copies;
- The randomness of this event is relevant even to the point that, according to the operator, when the machine was throwing out light copies and when using the duplex, sometimes the duplexed copies would be good on one side and light on the other or they could be light on both sides.

Anyone ever got one of these?

Cheers!

[jeroen2005]

Hi MrWho,

Had the same problem,replaced Drum,developer,developer unit ,Charging corona,Transfer/Seperating corona with same result.After replacing Potenial meter assy(55VA-2080) and Toner control board assy (55VA-9510) problem was gone.

Jeroen2005

[mrwho]

Thanks for the tip! I had ruled out anything toner-related since, acording to the operator, the machine would sometimes solve it after cycling the power (and if that would be so, the machine wouldn't have time to replenish the toner before taking the first copy out, at least I think not).

But I'm willing to try anything (I was just going to buy a couple of black cats to sacrifice them ) but I'll try it and then I'll tell you how it went!

Thanks!

[langelot]

My First thought...

...would be that you are either losing your bias current or (more likely) you might have the the high voltage power supply for the transfer/separation corona going bad. Its located in the ADU in the rear around the trans.sep. section. An easy way to confirm this would be to interrupt the machine by opening the door in the middle of making those blank copies, then pull out your drum carriage and check the drum for a latent image. If it is there, then you can probably blame either the high voltage power supply or the trans./sep. unit itself.

If the latent image isn't there, I would be inclined to think that your laser write unit might be going bad and run some teset charts and LD! & LD2 patterns to find out for sure.

Hope this helps.

[mrwho]

Thank you all for your feedback.

Trouble was solved by replacing the transfer corona's HV board (located on the backside of the ADU). The corona sometimes failed, causing the paper to scrap the underside of the drum assembly, ergo causing the light copies (and sometimes jam too).

An alternative cause for others with the same problem are the front door switches - before replacing the HV board, I replaced those and it reduced the trouble ocurrences, so check it also if you have this kind of problem!

Rep points to the kind gentlemen who replied to this thread! Thumb's up!