MPC-4500 Yellow printing only on 1/4 of the page

[Yeeter]

From what I have read here, there might be a couple different possible problems:

1) PCU
2) Transfer Belt tension
3) Dirty laser shield glass

The PCU's in this one have been replaced with a generic model from a previous owner, so they are not color specific. And its not obvious to me that the transfer belt tension is way off (stepped through the service manual on this, but it seems set by a compression spring to determined tension)

Before I swap the PCU - something else I should be trying first?

[ruben]

What happens if you print a sky-shot with background colour set to yellow? Does the colour just suddenly stop, does it gradient out or does it stop and start several times?

[Tonerbomb]

sounds like a charge roller may not be completely seated in the PCU.

[jonhiker]

check the rollers on the ITB. last time i had this same issue, one of the rollers had popped out of it's bracket.

[Debs1964]

sounds like a charge roller may not be completely seated in the PCU.

I'd have thought if the charge roller wasn't clipped in you'd get an SC code, or dark copies.
Sounds like a dirty laser slit glass or contaminated doctor blade in the dev unit to me

[collme]

check the rollers on the ITB. last time i had this same issue, one of the rollers had popped out of it's bracket.


I'd have thought if the charge roller wasn't clipped in you'd get an SC code, or dark copies.
Sounds like a dirty laser slit glass or contaminated doctor blade in the dev unit to me

I would agree with both of these solutions. if charge roller is not fully clipped into place you will get heavy background from that pcu as Debs says so either tension roller under itb belt for yellow pcu has dropped out of position or slit glass would be my first checks. both easy to check before going for 3rd option of dev unit doc blade.

[Phil the copy guy]

If the problem only presents itself on yellow replaced PCU unit

[Tonerbomb]

I'd have thought if the charge roller wasn't clipped in you'd get an SC code, or dark copies.
Sounds like a dirty laser slit glass or contaminated doctor blade in the dev unit to me

Sometimes you'll get the sc code sometimes you get solid toner coverage on 1 side. The dirty slit glass won't do this as the laser would have to wright the all dark image, and a dirty glass gives less laser light making the image lighter. Bad DV unit could also be the cause.

[Phil the copy guy]

​If you can make a good blacktop me you can make a good magenta copy and you can make a good cyan copy that is the yellow unit this is not rocket science

[collme]

​If you can make a good blacktop me you can make a good magenta copy and you can make a good cyan copy that is the yellow unit this is not rocket science
maybe not. the itb has 4 rollers inside that press the belt against the drums, these have dropped out at one end before giving part copies on 1 colour but good copies on the other 3. so check itb before buying and fitting a dev unit and/ or drum unit.

[Phil the copy guy]

Call me from in from of machine I can help you trouble shoot in less than ten min. I have an extra yellow unit in good working order that you can have if you need it!
413-429-6467 after 9 am est. tomorrow

[Yeeter]

It prints yellow across the lower 1/4 of the page only.

All other colors seem to work fine.

Its a fade - meaning the very bottom is full yellow, and then it fades out to nothing by about 1/4 up the page.

[Tonerbomb]

Call me from in from of machine I can help you trouble shoot in less than ten min. I have an extra yellow unit in good working order that you can have if you need it!
413-429-6467 after 9 am est. tomorrow

props to you to be this willing to help!! I would've sent this info via PM though as I would'nt want ZAZA or aab1 calling also... just my 2 cents worth....

[ucinn]

My first guess would be ITB also, have seen it before.

[Yeeter]

Update:

I never did find a copy tech via the phone book (amazing how hard it is to locate a copy tech willing to service personal equipment, it seems only interested in ongoing service contracts)

But I DID find a tech via this forum post - so thank you copytechnet! (and for the record, I paid the asking rate and am quite satisfied with the results)

In the end it turned out to be a bad laser unit. Worst of all worlds, but swapped and fixed now and printing great.

Now.... still wandering through the maze of 'scan to email' setup/troubleshooting with no luck, but thats another post.

Thanks to everyone for all the insights!

[Iowatech]

From what I have read here, there might be a couple different possible problems:

1) PCU
2) Transfer Belt tension
3) Dirty laser shield glass

The PCU's in this one have been replaced with a generic model from a previous owner, so they are not color specific. And its not obvious to me that the transfer belt tension is way off (stepped through the service manual on this, but it seems set by a compression spring to determined tension)

Before I swap the PCU - something else I should be trying first?

Kind of looke like the polygon mirror faces for yellow are somewhat covered with dust or toner or something. I haven't seen this on Ricohs, but I have seen that enough times on HPs that I thought I'd suggest that.

[SargeNZ]

I would have checked the laser shutter was working correctly or removed it altogether, as these can cause fading when they do not open properly.