HP 4550 Intermittent fading of CMYK

[bradjo]

I have a very low use (< 14,000 pages), HP 4550 Color Laserjet. It suddenly started fading all colors. You can see images of the problem:
http://bradjo.imgur.com/

I have tried:
1. Swapping all consumables (I use ONLY HP OEM consumables),
2. Cleaning laser mirrors & entire printer

I've taken the printer apart and completely cleaned it and the laser mirrors (the mirrors were pristine), and on the power supply there are 2 sets of paired ferrite beads, FB3 and FB4 they both appear to have blackened the circuit board. See the image here:


The fuse on the 110 power supply board is good which makes me think it's not the power supply. What else could possibly be causing this?

The high voltage power supply boards A & B are both pristine. Although I have not tested them and do not know how to test them, help?
Thank you for any help you can offer,
Jo

[Compman55]

Although discolored, how are the solder joints on the backside? Sounds like DC power problem.

[MichaelTech]

Your showing just the P/S, but have you checked the H/V contacts? A faulty one could affect the fuser, and may cause the fading. Drum drawer contacts, on the sides of the drawer, and the small round spring-loaded contact inside, top, to the right.
Simply a bad scanner will do this also. A bad toner board, mounted on the rotary drive, and/or dirty contacts on the toner carousel.
I always strip them down almost completely, and clean, clean, clean! Good luck.

[bradjo]

Although discolored, how are the solder joints on the backside? Sounds like DC power problem.

The solder joints look fine and the HVPS board was pristine as well. I replaced with a refurb power supply and it had the same blackened Ferrite Bead spots.

Your showing just the P/S, but have you checked the H/V contacts? A faulty one could affect the fuser, and may cause the fading. Drum drawer contacts, on the sides of the drawer, and the small round spring-loaded contact inside, top, to the right.
Simply a bad scanner will do this also. A bad toner board, mounted on the rotary drive, and/or dirty contacts on the toner carousel.
I always strip them down almost completely, and clean, clean, clean! Good luck.

The H/V contacts look almost new and I cleaned everything. The Drum drawer contacts are all good. I cleaned all contacts etc..... and put the printer back together and got a good print or two and then it went right back to fading everything.

I'm stuck. I hate to get into swapping parts (like I did with the power supply), since that can rapidly get expensive since I don't have an extra 4550 to swap with, so is there a way to check the board first?
Thank you,
Jo