laser-lovers@uw-beaver (04/09/85)
From: ihnp4!utzoo!henry@uw-beaver.arpa
We're encountering an odd problem on one of our LaserJets. Almost
certainly the problem is in the Canon print engine, so it should be
generic to other small-Canon-based printers. Low on the page, in two
quite distinct vertical bands, we get what we've been calling "the
smudgies": the characters themselves are clear and sharp, but they've
also got gray shadows underneath them. The severity varies. The only
correlation we can find with the physical structure of the printer is
that two of the diagonal wires which keep the paper out of the slot
holding the transfer corona wire are in just the right places to line
up with the bands in which the smudgies occur. Cleaning the wires does
not help, nor do any of the routine cleaning operations. Putting in a
new toner cartridge does not consistently help. It's annoying enough
that we're thinking of calling in maintenance, but first... has anyone
got any thoughts on this?
Henry Spencer @ U of Toronto Zoology
{allegra,ihnp4,linus,decvax}!utzoo!henrylaser-lovers@uw-beaver (04/10/85)
From: jp@LANL.ARPA (James Potter) > From: ihnp4!utzoo!henry@uw-beaver.arpa > > We're encountering an odd problem on one of our LaserJets. Almost > certainly the problem is in the Canon print engine, so it should be > generic to other small-Canon-based printers. Low on the page, in two > quite distinct vertical bands, we get what we've been calling "the > smudgies": the characters themselves are clear and sharp, but they've > also got gray shadows underneath them. The severity varies. Amazingly enough I had a similar problem which I also called the smudgies. I guess thats a very descriptive word for it. HP maintenance people thought that they had cured a similar problem on another one by replacing the transfer corona power supply. They tried that on mine without success. Then they went through the whole system replacing every part of the engine. They were almost out of ideas when they realized the only part they hadn't replaced was the feeder guide assembly (Fig. 8-17 in the service manual). They didn't have such a part in their spares kit, but decided to borrow the one from their 'loaner'. Voila! No more smudgies. The then put their loaner back together and ordered the replacement for mine. While I was waiting, they let me use their loaner. While I had it I noticed that it too had a slight case of the smudgies. I compared the location of the smudge with the structure of feeder guide assembly and found that it lined up with, and was the same width as a space between the plastic ribs. When I removed the assembly I found that this space contained a thin sheet metal 'ribbon' that is part of a piece called the Plate, Fusing Feed. I pushed up on this metal piece, deforming it slightly, and reassembled the printer. AHA! No more smudgies. I believe that the function of the metal is to help drain off remaining charge before the paper enters the fuser. The effectiveness seems to be critically dependent on the proximity of the metal plate to the paper. I think mine may have gotten bent slightly during recovery from a paper jam. When I received my repaired printer, the smudgies were gone and have not reappeared a couple of thousand sheets of paper later. This problem seems to be a feature of the Canon engine and the HP people should be becoming more familiar with it. Let me know if this turns out to be the same problem as you are having. Jim Potter jp@lanl.arpa