HP M479 contrast problem

[Profibastler]

Hello Folks,
the HP Laserjet Pro M479fdw with contrast problems.
Original Toner built in, calibration ok.
Laser scanner (all mirrors) has cleaned.
In Service mode isn`t anything find to adjust colors.
What should i do again.
See attached demo print.
THXM479.jpgM479_2 (2).jpg

[Tricky]

Re: HP M479 contrast problem

On the drum cartridge tray, there is a metal spring on the left-hand side that touches the silver roller on the black drum, is this making contact, you should see it move slightly when you insert the drum.

[Profibastler]

Re: HP M479 contrast problem

@skynet THX for reply, but the problem iM479_3.jpgs with all colors the same.

[Tricky]

Re: HP M479 contrast problem

Can you print a supplies status page and upload it here?

[Profibastler]

Re: HP M479 contrast problem

M479_3.jpgM479.jpg

[Tricky]

Re: HP M479 contrast problem

Have you tried it with another complete set of toners?

Your black and yellow toners look like they are leaking, the registration patch sensors may be dirty, although I doubt that is the root cause. Check the ribbon cable that goes between the engine pcb and formatter if the cable contacts look bad or frayed, trim it with a pair of scissors.
Lastly, change engine pcb

[JtechC]

Re: HP M479 contrast problem

Are there any errors/codes?

I've seen this before on the M477 series as well. I think it was the Density Detect sensor that needed to be replaced on one machine. RC4-3728
And another machine the ground tab on the cartridge drawer was bent way out of position.

[Profibastler]

Re: HP M479 contrast problem

Hello @JTechC, can you please tell me position of the ground tab?

[JtechC]

[Tricky]

Re: HP M479 contrast problem

There is also a metal spring on the left-hand side of the machine body that is usually in contact with the metal frame of the cartridge tray, that I think provides the grounding. If this is deformed, it won't make the electrical contact correctly.

Edit : Noticed a weird bug with the scanner, to replicate the fault the machine needs to be switched off, it won't work if the feeder has been used.
Turn the machine on and copy off the glass, it scans the document twice, you can fix this by using the feeder once. I don't do firmware updates on these.

btw the printer is factory reset..

[Profibastler]

Re: HP M479 contrast problem

Every color has one.
But my mistake affects all colors.
The flags are good looking.IMG_20230926_184417[1].jpg

[JtechC]

Re: HP M479 contrast problem

Those look ok from here.
Do you have another cartridge tray you can try?

[Profibastler]

Re: HP M479 contrast problem

Changed tray now, nothing fixed. Same problem.

Those look ok from here.
Do you have another cartridge tray you can try?

[JtechC]

Re: HP M479 contrast problem

I would swap cartridges one at a time to see if the issue changes.
If no changes, swap the transfer belt.
if no changes, I'd swap the density detect sensor. rc4-3728

Are there any error codes?

[Profibastler]

Re: HP M479 contrast problem

How to disassembly the detect sensor, please?
Can`t find anything about in SM.
It`s built into the ITB?
No error codes occured.

I would swap cartridges one at a time to see if the issue changes.
If no changes, swap the transfer belt.
if no changes, I'd swap the density detect sensor. rc4-3728

Are there any error codes?