HP Laserjet Printer

[alexsmith2709]

I do a lot of printer repair as part of my business and a particular problem i'm having with my in-shop printer is baffling me and was wondering if anyone here had any experience with HP/Canon Laserjet Printers? I have an HP M775F multifunction that we are having alignment issues with. No matter how much calibration or resetting the calibration we do, we cannot get the printer to align.

I have changed cartridges, both OEM and non-OEM types, I have changed the ITB (transfer belt), the fuser, the registration sensor, the first, second and developer high voltage boards and the laser scanner unit, none of which have solved the problem. A few years ago the formatter board and Interconnect board were also replaced.
I have been working with my supplier of remanufactured toners to see if they had any ideas and they even brought in their supplier to help and none of us have any ideas at this stage.
Before i throw this printer into the road, does anyone here have any other suggestions?

 

[Markverhyden]

Can you please post some samples. Preferably a multipage document.

 

[alexsmith2709]

Here you go. Ignore the lightness, thats just the scan not picking up the yellow very well, it does print fine. As you can see, particularly on the colour band test the colours are not aligned.
https://we.tl/t-0D1NH2iRaj is the link as the file is too large to attach

 

[Markverhyden]

Does this happen on all trays?

 

[alexsmith2709]

Yeah, all trays, all paper types that i've tried.

 

[HCHTech]

I was going to bust your chops for spending so much effort on a printer, but I just looked it up, haha. That's a significant piece of hardware! I had a color laser a few years ago that I scrapped for this same reason (also an HP, btw). It was probably fixable by someone who knew them inside & out, but I just couldn't waste time on it. I paid half it's purchase price for its replacement (also an HP), which is better and faster.

 

[alexsmith2709]

I was going to bust your chops for spending so much effort on a printer, but I just looked it up, haha. That's a significant piece of hardware! I had a color laser a few years ago that I scrapped for this same reason (also an HP, btw). It was probably fixable by someone who knew them inside & out, but I just couldn't waste time on it. I paid half it's purchase price for its replacement (also an HP), which is better and faster.

It was a decent bit of kit back when it was new about 6 years ago. We use it all the time so this is a massive pain having it down for so long. Spending a couple hundred on parts when a new machine is going to cost me around £6500 +VAT seems worth it, but at this stage it looks like im going to have to buy a new one as i've replaced every part i can think of. I now know this machine inside and out

 

[Markverhyden]

Every registration issue I've dealt with has been handled by what you've done. I did look in the troubleshooting manual and they mention you can drill down into general settings>image registration>adjust tray to make manual adjustments. Link below in case you don't have the doc, page 209.

https://central-it-service.com/owncloud/index.php/s/VrHkw5YMafSUdri

 

[nlinecomputers]

You probably have a bent spring in the registration shutter or the secondary transfer roller is bad.

 

[alexsmith2709]

I have tried adjusting the image registration, that moves the whole page, not individual colours.
@nlinecomputers i replaced the registration sensor so this part is brand new with no damage. The secondary transfer roller was something i did consider, but my usual parts supplier doesnt currently have one so i may look elsewhere for one. I have read the toubleshooting/repair manual and understand what this roller does, but i cannot see how it discharges the paper to remove excess toner (in simple terms) as there doesnt seem to be any contacts that i can see, its a foam roller that sits in plastic clips.

 

[nlinecomputers]

I'm talking about the shutter, not the sensor but if you did any work in that area you might not have gotten the parts exactly back in place or you might have accidentally broken a part putting it back together. Or a paper jam might have dislodged it. The transfer roller's foam is antistatic and can dissipate static. The reason I mention it is because a nick in the roller could cause the paper to hang and get skewed. Damaged or worn Rollers along the registration path are the most likely cause of skew.

 

[alexsmith2709]

Isnt the shutter on the sensor bar? There is a shutter on either side of that sensor bar, i assumed this is what you were talking about as these are spring loaded. This is what i replaced.
I actually cleaned the secondary transfer roller this morning, it didnt have a nick in it, but it did have lots of paper dust and excess toner. Putting this back in and calibrating again and we have a near perfect print again, so i think this may be the problem part. I am going to monitor it over the next few days and if required try and buy a new roller. My supplier has a 14 day lead time on this part they told me today.