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NeXT 400dpi laser printer restoration

Do you mind sharing a link to this app?

Thanks for feedback, I hope sharing our experience will get us closer to fixing our printers.

The ”PP” (“Printer Properties”) app is available in the “Nebula” CD-ROM archive. Unfortunately, there’s no documentation, let alone the source code.

It’s useful, but I would not trust it 100% for problem shooting. It’s clear, for example, that “Paper jammed“ error it’s not because of actual paper jam, and so on.

There’s a low quality scanned copy of the service manual for the printer, with a lot on information about the way it works, but unfortunately the most interesting part (the appendix) is incomplete, like in an Indiana Jones movie…

Similarly, so far I’ve not been able to find any documentation about the printer port and the communication protocol with the main unit.

So, it’s trial and error on the hardware side.

On my end, after replacing the many caps that were visibly damaged and getting in return ”just” a change in the nature of the error code, I decided to go all in and replace all the caps (still to be done).
 
The ”PP” (“Printer Properties”) app is available in the “Nebula” CD-ROM archive. Unfortunately, there’s no documentation, let alone the source code.
Thanks! For sure it's better than what comes with the default OS

Yeah, it's frustrating not having the complete service documentation, but at least there's something.

I'll update you on the progress, and when I get to a point where it works maybe we can figure something out.
 
What kind of interface does the printer use? Maybe it could be connected to a PC for more information, or a meaningful error code.
 
It's a DE-9 port with a proprietary serial protocol. There's a chance it can be reverse engineered but I don't have tools for such tasks
 
Could it perhaps be similar to LocalTalk (230k async serial) given the Apple roots of NeXT? If it is connected via a Zilog SCC, its certainly possible.
 
Update from my side.
I have recapped all I could (AC/DC/HV/LB), with the exception of the biggest ones in the Driver and Sensor unit, as - stupid me - I ordered the wrong size and they didn’t fit.
Some of the smaller caps were busted and leaking, some were out of tolerance, but the majority of those I could actually measure were still nominal.
So, I am fairly confident the big boys are still healthy…

The printer now gives more consistent signs of life, at start up the main motor spins for a second, as designed. Before recapping it didn’t.
Still unable to print, though.
What is puzzling me is that it behaves fuzzily. The same sequence of operations may end up with different results.

So far I have identified two potential residual issues.

1) The unit struggles getting ready.
I guess the fixing unit could indeed be the culprit.
It’s heating up, as you can sense the hot air being evacuated by the fan, but I suspect the thermistor struggles reaching the trigger level (at around 165 deg C) for setting the “RDY” status (where to measure it? Still unclear…).

2) Whenever the unit comes ready and starts “printing”, it seems as though the pick up roller clutch is not engaged, the rollers are not rotating. So, after a while you get paper jam error (which is a generic error).
I need to figure out if it is the clutch or the solenoid, probably I should replace the entire assembly, but sourcing it is not easy…
 
Further trials, I could finally get the first (and so far sole and last) page printed.
So, after recapping, the unit came back to life (still something weird going on, though…).
It’s hooked to a Cube 030 with NS 3.3, alternatively MO NS 1.0.
During the booting up sequence, at the very end, just before the login prompt, the unit is powered up, the motor spins for 1 second (making sometimes very clunky and scary noises, which is not a good sign…).
Once you are logged in, the printer takes some 2 minutes to warm up. At that point, I can send something to print, means the printer status is “ready”, which means that the fuser is at the right temperature.
First issue: the default state of the printer is “paused”, and it doesn’t wake up unless I open the Print Manager and push the button “Continue”. Shouldn’t be like that, I assume there’s still something wrong… (Note: if I boot from MO with NS 1.0, the default status of the printer is NOT paused, so it could be some software thing…)
Anyhow, after sending something to the printer, it takes some time before the job is ready.
Once it’s ready, the printer tries to load the paper. If it fails (in my case, it’s 100% of the cases), it throws the dreary “Paper jam” error and from there on it’s impossible to recover the situation, I have to restart the whole machine. Every time. Which surely is not normal either…

Main issue: the pick up roller. Or, better, in my case the combination of pick up roller and paper tray.
I have to say I’m not sure my printer is indeed 100% in original conditions, as the previous owner mentioned some attempts he made for fixing the faulty paper feed section.
So it could be that the pick up roller is no longer original.
Anyhow, I dismantled it, the rubber roller is in fact a chunky plastic roller sheathed by some 3 mm thick rubber sleeve.
To my eyes and to the touch, I would say the rubber sleeve is still sufficiently grippy. Anyhow, I removed the sheath, cleaned carefully with slightly abrasive “magic rubber”, then remounted rotated some 90 deg compared to original position.
Still, unable to load the paper.
My attention then moved to the paper tray, which in turn is not exactly in pristine condition.
First issue: the tray seems to lock the paper along the sides, A4 sheets are not accommodated neatly.
Second and main one: the position of the topmost sheet is not at the right level, it’s in fact too low, remaining locked in the tray.
I could see that there’s a pad in the front of the tray that has been replaced by something grippy and not at the right level, but my understanding is that - on contrary - it should be as frictionless as possible.

So, bottom line, by playing with the pad and by manually pushing a sheet through, I could get - by sheer chance - at least one page printed.
Sufficient for having confirmation that the rest of the printer is somehow healthy, which is already something.

So, I think I need at least a new rubber roller and a new tray, not sure I want to squander additional money on this project, though…
 
Wow, you managed to print a page.. can't be too far from the finish line?

This gives me confidence that I might get mine working, it is behaving like yours before the recap.

If any of those expired rollers can be replaced I would be interested as well, depending on availability and price...
 
Wow, you managed to print a page.. can't be too far from the finish line?

This gives me confidence that I might get mine working, it is behaving like yours before the recap.

If any of those expired rollers can be replaced I would be interested as well, depending on availability and price...

Would anyone please be so kind to share some pics of the rollers and of the tray pad, just so that I can assess mine. Thanks!
 
Quick update: by further tweaking the tray pad, I could get a few more test pages printed.
The output quality is not bad, the pages are still a little dirty, but the more I print, the cleaner they get.
Anyhow, I’m now almost sure the rubber roller or at least the outer sleeve has been replaced probably not according to the specs, so I am looking forward to comparing it to reference pictures before trying to source a spare unit / sleeve.
Important remark: the app “PP” seems to be returning the wrong status of the printer: it still throws “Fatal Error” message with focus on fixing unit & bad hardware, even though the printer can actually operate. I would not trust it too much.
Still very annoying and symptom that - hardware-wise - something may still be not OK: I cannot recover from “Paper jam” error in any other way than restarting the main unit.
IMG_0270.jpegIMG_1947.jpegIMG_0271.jpeg
 
Could you attach pictures of which parts you're referring to? I can try to match them. I think my tray should be in good condition, not sure about the rollers.
 
This is the tray pad I’m referring to, I guess it’s been modified.

IMG_3670.jpeg

And this is the rubber roller:

IMG_1945.jpeg
 
The tray looks like this and it feels like paper or cardboard

next-printer-7.jpg

Regarding the roller, it looks like yours but the C3 section is deformed and is more oval shaped now. The rubber doesn't feel bad but I'm worried that the deformation will cause problems.
 
If that is the sheet picker, the oval is normal. The tray self-adjusts with a spring to make sure the paper is always within reach of the picker roller. When the printer needs a sheet it cycles the picker roller one rotation which is deliberately grippy as to pull one sheet of paper from the top of the tray and into the feed rollers. The spring in the tray maintains upward pressure on the picker.
 
There are other printers that use a rubber belt/tier for the pickup roller. You may be able to find one with rubber that's close enough to fit.

As far as the dirty printing goes, I can guarantee it needs a new wiper blade in the toner cartridge. They have a shelf life of about 10-15 years maximum. Finding wiper blades for printers older than the laserjet 4 is difficult. As I said in an earlier post, I've had to modify available wiper blades to work with older printers.
 
Thanks to you all for feedback and support.

Paper tray. I’ve checked the LaserPrinter one and there’s nothing there, I assume it’s because it is coupled to a different roller.
My guess is that the function of the cardboard (or whatever) shim is to keep the paper sheet edge flush as it gets fed into the printer.

Rubber sleeve. Previous owner mentioned something about it, so maybe he replaced it with a thinner or thicker one.
In the NeXTcomputer forum some old post indicates the roller of the laserprinter II / III as the 1:1 replacement for the one of the NeXT printer, but to me it looks very different…
I could not get any factual feedback there, it seems as though the topic is not raising any interest.
Does anyone here have any direct experience about using it?

Wiper blade. Is it part of the fuser assembly or of the toner cartdrige? I’m not seeking for perfection, but maybe I will tackle that one, too.

Anyhow, the major annoyance I have now is the fact that in the trial and error process for fixing the paper feed section I incur 98% of the times in the “Paper jam” error and I am not able to reset the printer for attempting a second print without restarting the main unit, which takes forever (it’s a 030…).
Do you know any alternative, effective way for launching a second print job after the first one fails? Not even pulling the power chord works: the printer should reset, but in fact when you power it up again the main motor is not spun, sign that the main unit is still considering it in a different state.
 
There are other printers that use a rubber belt/tier for the pickup roller. You may be able to find one with rubber that's close enough to fit.

As far as the dirty printing goes, I can guarantee it needs a new wiper blade in the toner cartridge. They have a shelf life of about 10-15 years maximum. Finding wiper blades for printers older than the laserjet 4 is difficult. As I said in an earlier post, I've had to modify available wiper blades to work with older printers.
This is also interesting, refurbishing the toner cartridge for the Laserjet.

 
Man that looks complicated, can't even buy a NOS one if they're all expired.

Have you checked the other videos? One of them covers checking sticky solenoid dampers of the Laserjet II and it looks similar to the ones in the NeXT printer. It might also cause paper jams... mine are not too sticky.

I'm almost done with the recapping, just waiting for the missing ones. Did you change the small 0.1uf 50V capacitor on the motor board (C601)? Could I also swap it with a film cap?
 
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