breadbooze

asked Oct 28, 2009 at 7:28pm
Hp HP LaserJet 5SI

HP 5si printing "blobs"

I have two HP 5si's in the office that have performed well over the years. Both suffer from small problems every so often and regularly see HP maintenance kits installed. Recently one of them started act up and printed "blobs" on sheets, rendering any print outs unusable. A scan of a page is here-

http://farm3.static.flickr.com/2689/4054722774_de83779305_b.jpg

I have literally tried everything to figure out the cause of this. First by swapping toner/fuser with the good unit, then putting brand new toner/fuser in there. I've swapped out the DC controller, the high voltage supply, then the low voltage supply, and finally the laser assembly, all to no avail! The blobs are random and there is no contiguous pattern of blobs from one page to the next. Everything inside the printer is as clean as it can be. Can anyone provide a clue as to what's going on? Will I have to test continuity for every wire on every connector going to the DC controller?
Boy that is nasty looking. Toner can only come from the toner cartridge or residual toner from a previous image from the fuser. I would lean towards the toner cartridge and possibly a voltage issue. Try doing a couple of half tests by putting paper on the manual feeder doing a self test and when the back edge enters the printer open the toner door to stop the printing. Do it until you get the defect since it really does not look like a fuser issue and then look at the drum as it could be a contact issue where voltage is arching and causing the toner issue. Since you changed the high voltage ps I doubt the contacts at the back of the printer are bad so I would check the grounding contacts at the front of the printer that make contact with the toner cartridge.
by dmzcompute on Oct 28, 2009 at 8:04pm Add comment
Earlier this week I saw the same symptom for the first time, in many years of printer servicing. It is, as DMZ suggested, a grounding issue. A colleague had very similar printouts, and when the client told him that they had trouble installing the cartridge, he checked and found an earth lead out of place. Sorry I can't be more specific.
by unknown on Oct 28, 2009 at 8:22pm Add comment
Fantastic, I will check the grounds first thing and post an update here.
by breadbooze on Oct 28, 2009 at 9:40pm Add comment
Had on similar to this too before, copper clip was messed up under the transfer roller assm. I think that is what Aussie was referring too also.
by Anonymous on Oct 29, 2009 at 6:07am Add comment