hp 3800 all magenta backgroud

[Iman]

Hi all has anybody seen a problem on the hp 3800 where the background is all magenta.If I switch the magenta drum with the cyan then the background is fully cyan.The image is on the page but just full magenta background.I havent worked on these machines before but it seems to me that the transfer unit is faulty.Any help would be much appreciatated.
Thanks

[prntrfxr]

hp 3800 all magenta backgroud

Why would the transfer belt cause a problem with only one slot?
Transfer belts transfer every color the same way. If it was a transfer belt it would have affected ALL the colors not just one.

Begin with printing an engine test (press engine test button) - an engine test will bypass the formatter. If the print is good, you have a bad formatter.

Check contacts that make contact with the cartridge. If they are misshapen or broken, replace them.

If you still have a problem, it will be either a bad HVPS or DC Controller. (More likely HVPS than DC Controller. That's why I listed it first.)

My recommendation is: Buy a service manual for this machine. It is not a 4000, and if you're not familiar with it you'll end up making a bigger problem. I'm trying to save you a headache here. Hope this helps you

[ExOceMan]

Sounds like an issue with bias voltage not retaining the toner in the developing unit. Or if your drum wasn't getting charged correctly you would have a problem like this.

[Iman]

Thanks for your input Prntrfxr.I plan to check the laser head and hv supply and contacts for the drum.As I say i'm not familiar with this machine.I thought there was four transfer rollers within the belt each responsible for transferring a separate colour.I have seen transfer rollers arc and cause such a problem on copier based machines.Thats why I was leaning towards the belt unit but will take your advise on board.
Thanks

[prntrfxr]

hp 3800 all magenta backgroud

I plan to check the laser head and hv supply and contacts for the drum.

Why are you checking the laser head?