PDA

View Full Version : No blue print from colour printer



andrew93
16-08-2005, 02:26 PM
Hi everyone

I'm working on an HP LaserJet 4600 colour printer and it is not printing any blue colour at all. The printer is just out of warranty and has me stumped.

On occasion the printer has a very slow warm up and sometimes doesn't get past the 'initialising' stage at all, which requires a restart. However, that seems to have stopped after I re-seated all of the cables.

The diagnostic page(s) say that all is ok, the cartridge is full, and the printer prints but it simply refuses to lay any blue toner onto the page. I have tried three different toner cartridges, no change. Changed the blue scanner, no change. Changed the formatter board, no change. Changed the denisty sensor, no change. Re-seated all of the electrical cables, no change.

Any suggestions as to what to try next?

Thanks in advance
Andrew

Graham L
16-08-2005, 02:34 PM
Perhaps it doesn't like National. ;)

I'd try asking HP service about this. If it's only just out of warranty they might be nice. Obviously you're dealing with this at a nuts and bolts level already, so you won't appreciate being advised to load the latest driver or reformat the disk or the currently popular advice to "reflash the BIOS". :D

All I can think of is the high voltage supply to that cartridge. I guess there's only one transfer point. (Just thought ... does an image form on the blue drum? That might show whether the drum is getting charged.)

andrew93
16-08-2005, 03:04 PM
Perhaps it doesn't like National. ;)
{snip}
All I can think of is the high voltage supply to that cartridge. I guess there's only one transfer point. (Just thought ... does an image form on the blue drum? That might show whether the drum is getting charged.)

Very funny - being election year and all that! :D

We too think it is to do with the connection between the printer and cartridge (hence the cable re-seating etc.) - we have cleaned the contact points and tried 3 different cartridges. There is no blue toner on the drum within the cartridge but the drum has turned (we marked a point on the toner cartridge gears). Plus we have checked the cartridge door is opening when the ETB door is shut. Good question though! Any other thoughts?

Andrew

Graham L
16-08-2005, 03:41 PM
I'm just going by my general knowledge of how the things work, rather than detailed repair experience. (I've been buying laser printers at $5 when I want them so don't even change empty cartridges).

How does one measure (or check presence of) the HV going to the cartridge? It's several kV, even though at very low current, so there are probably interlock switches to shut down the supply when the unit is open. (A neon screwdriver might light up?). In each cycle, the drum has to be charged evenly by a corona wire, then the light beam discharges the places where toner is wanted. Then, in the developer area, charged (the same polarity) toner is attracted to those spots and repelled by the places still charged. Then (oppositely charged, or neutral?) paper attractes the toner. I suppose there is only one connection for HV on the cartridge. Does the same supply feed all the cartridges, or is there one supply per colour? Can you try pinching the cable from one of the working colours and using that to feed the blue one's connector?