C450, 2 colours went crazy, pro-knowledge needed

[Wappla]

OK, and here is a complicated issue. In fact the one why I re-registered at this forum.

It is about Cyan and Magenta of our C450, that went absolutely crazy after changing the transfer belt. The last weeks the copier was not ok anymore, because of a damaged cleaning part of the transfer belt (I had a complete sheet inside the cleaning part!), so I got a new belt and installed it. Subsequently the Cyan and Magenta showed the prints you can see attached, while Black and Yellow are fine. So I as well changed the two Imaging Units. As this did not change the situation, I feared that perhaps my new imaging units were stored in wrong condition for too long. So I changed the Magenta imaging unit again. And you know what: it has 100% exactly the same issues like the one before! You can see it in the scans I made, It is really exactly (!) the same - so it cannot be connected to the imaging unit.

As Yellow and Key is working well, it can also not be connected to the new belt, or am I wrong?

What I tried so far after installing the new belt and the new imaging units:

-) installing a new waste toner box
-) installing a new paper dust filter
-) installing a new transfer roller
-) Installing new toner (always original toner at our place)
-) vacuum cleaned the toner place and the place of the imaging units
-) cleaned the LPH Assy
-) changing the network cable between Firery and copier to a brand new one
-) moving out the cable between Firery interface board and copier and cleaned all the contacts with IPA as far as possible (some 10+ technician fixed this machine several years ago, when it blurred massive red fog over the complete sheets, by just reseating this interface cable).

-) In service mode all the image process adjustments
-) Gradation Adjust
-) TCR Toner Supply
-) played with D-Max density, TCR Level Settings and Background Voltage Margins without any effect

-) At the Firey restored the X3eTY calibration information to factory defaults by using ColorWise Pro

Whatever I do, there is nothing changing, not even slightly moving. Cyan and Magenta show exactly the same strange prints. For me there is no explenation at the moment, as the C450 worked fine 2 months ago, and everything started with replacing the belt with a brand new one.

Plase tell me what I should try next.

[blackcat4866]

I think I would take a look at the movement that presses the primary transfer rollers down (inside the primary transfer belt). On Toshiba's it's fairly common for those bushings or levers that move the individual primary transfer rollers can break, so you're only getting pressure at the front or the rear. When whole primary transfer assemblies are shipped, I have seen those primary transfer rollers drop right out of the unit, just from being jostled.

It's very easy to assemble those parts incorrectly when installing a new primary transfer belt.

[Wappla]

To be sure, that we are understanding each other correctly (sorry English is obviously not my first language): I did change the 2nd transfer roller, not the rollers inside the belt.

And if your idea of pressure/no pressure from the belt would be the cause, such a test pattern like below could never happen? Or am I missing something completely? BTW the small black dots inside the other colours are dirt from my scanner, that I did not clean right now before scanning

4c.jpg

EDIT: and once again: this is a brand new belt, and brand new Cyan as Magenta imaging units. At all I have now 5 imaging units at these two colours behaving 100% similar! And there were no problems before I installed the new belt last week, …

[mix0730]

Check High voltage and Contact

[Wappla]

So you are suspecting an "Drum Charge Corona malfunction"? Any idea how that could happen, just by changing the belt? Anyways, if I read correctly, HV1 is responsible for the drums. How do I exactly check the contact? The SM only describes how to change HV completely. Do you mean just checking all the connectors at the HV1 board, or any other connectors? Or do you mean some special measurements, to see if it is causing the problems? That might mean I would need a step by step guide through, as non-pro, …

[kingarthur]

I'm with blackcat, I'd suspect the transfer belt. Many a time, on the older devices, the transfer belts would be damaged when unpacked, usually the 1st transfer rollers inside the belt had popped out of position, or one of the springs have popped out, or a plastic lug that moves the 1st transfer roller into position has snapped off. Take out the transfer belt and give it a good examination, even better if you have the old one, to compare it with. If you look at the below diagram, you have your drums/image units, Y,M & C, directly above them you have the 1st transfer rollers, then above those, you have the levers than push them into position, check that those levers are still there, and also the springs are still on them.

image.png

[Wappla]

Ah, now I understand. And now it makes sense why it is connected to the belt. Thanks a lot. Yes, I will check it, and try to fix it. And I do still have the old one!

[blackcat4866]

I'm with blackcat, I'd suspect the transfer belt. Many a time, on the older devices, the transfer belts would be damaged when unpacked, usually the 1st transfer rollers inside the belt had popped out of position, or one of the springs have popped out, or a plastic lug that moves the 1st transfer roller into position has snapped off. Take out the transfer belt and give it a good examination, even better if you have the old one, to compare it with. If you look at the below diagram, you have your drums/image units, Y,M & C, directly above them you have the 1st transfer rollers, then above those, you have the levers than push them into position, check that those levers are still there, and also the springs are still on them.

image.png

Yes, that. Is this better?

Ich denke, ich würde einen Blick auf die Bewegung werfen, die die primären Übertragungsrollen nach unten drückt (innerhalb des primären Übertragungsbandes). Bei Toshibas ist es ziemlich üblich, dass die Buchsen oder Hebel, die die einzelnen primären Transferrollen bewegen, brechen können, so dass Sie nur vorne oder hinten Druck bekommen. Wenn ganze Primärübertragungsbaugruppen versandt werden, habe ich schon erlebt, dass diese Primärübertragungswalzen einfach aus dem Gerät herausgefallen sind, nur weil sie angestoßen wurden.

Es ist sehr einfach, diese Teile falsch zu montieren, wenn man ein neues primäres Übertragungsband einbaut.

[Wappla]

No thanks, thats not better
I meant that my English is not enought for 100% accurate description. I thought that you thought I installed the primary rollers and thus damaged something inside the belt. Together with the fact that I was not aware that there is a roller for every colour, I did not understand you, until I saw the diagram kingarthur posted.
I will report after the weekend, what happened.

[kingarthur]

No thanks, thats not better
I meant that my English is not enought for 100% accurate description. I thought that you thought I installed the primary rollers and thus damaged something inside the belt. Together with the fact that I was not aware that there is a roller for every colour, I did not understand you, until I saw the diagram kingarthur posted.
I will report after the weekend, what happened.

just to confirm, the rollers are inside the transfer unit, it's usually really obvious if they have popped out. with the levers, they may look ok, but just have a closer look, to make sure that the plastic pins they sit in haven't snapped

[Wappla]

Thanks for your advice! It's highly appreciated. Let me see when I find some time to care about the belt and its rollers.

EDIT: I replaced the Cleaning Unit (4049-311) of our old belt, with a new one, and now the machine is back with best quality with the old belt and its new cleaning unit. So it was the new belt! Thanks for your support, also the idea with HV, even if I am extremely glad it was only the belt! As promised I will report about the belt and its rollers as soon as i know more.

[Wappla]

I'll get a refund from my recent supplyer. He already sent a new belt a Friday. Today he told me, that I shall wait until I checked the new one, before he tells me if I should send the broken one back or not. So I do not like to disassemble it, if there is a possibility that the supplyer wants it back, …
But that poses another problem to me. A new belt is registered at the copier with a resistor that is melting at the first usage, like the fusing units, isn't it? So how should I test a 2nd new belt, without loosing 300k copies?

[mjunkaged]

I'll get a refund from my recent supplyer. He already sent a new belt a Friday. Today he told me, that I shall wait until I checked the new one, before he tells me if I should send the broken one back or not. So I do not like to disassemble it, if there is a possibility that the supplyer wants it back, …
But that poses another problem to me. A new belt is registered at the copier with a resistor that is melting at the first usage, like the fusing units, isn't it? So how should I test a 2nd new belt, without loosing 300k copies?

I don't think you'll use up the count from the first fuse reset, and pico fuse can be replaced if your 1st belt is good on the 2nd belt he's sending you. Just don't run thousands of test copies, the machine shouldn't lock you out on transfer belt count until AFTER you've printed that many pages.

Good call, not taking it apart. I hope we're all aware that the C350/C450 have NO LASERS and it's an LED print head? YOU typed LPH so not sure if you meant 'laser' or 'LED' in your post. Dirty LED on either color WILL cause the pictures. SO while you're waiting you can clean off LED heads and check contacts for I/U's at rear of I/U cavities with a flashlight..
You're also correct that the I/Us are all old new stock at best, if not reman. so I've seen a high failure rate as well from storing/shipping on end (hence the OEM diagonal box ends) and failed developer material (carrier for the toner) from SHEER OLD AGE AND TIME. And had plastic parts on "NEW' I/U's shatter like dust. MUST shake the I/U horizontally back and forth VIGOROUSLY to evenly level out the toner/dev. clumps even on NEW OEM.