NeXT 400dpi laser printer restoration

[powerlot]

Hi all

I realise that printers are boring, but I wanted to give this one a go as in the end, having a laser printer for bulk b&w printing wouldn't be a bad thing to have.

The problem with the printer is that it doesn't budge when the PC sends a document to the printer queue. Sometimes there's a split second of movement and it feels like something is jammed, but there's no errors and the document is stuck in "printing". No attempt to pick up paper whatsoever.

It's a black box (pun intended) to me...usually printers are pretty vocal about their problems. Is there a way to find out what's wrong with it?

NeXT 400 DPI Laser Printer Brochure from 1992 : NeXT Computer, Inc. : Free Download, Borrow, and Streaming : Internet Archive

Brochure for NeXT 400 DPI Laser Printer from NeXT Computer from 1992

archive.org

Thanks a lot

PS: When I open the lid the computer complains about an open lid, as well as when selecting manual feed and no paper is in the manual feeder. That's about it.

 

[booboo]

I haven't played with a NeXT printer since we originally sold them When you say "PC" what are you referring to? The DisplayScript renderer was on the NeXT, doing most of the work.

 

[powerlot]

Sorry, I'm referring to the NeXT computer where I attached the printer (wrote PC out of habit). It queues the print job but then after a brief movement nothing happens.

 

[andy]

The first thing to do is closely inspect all the boards for leaking capacitors. The early 90's was prime time for defective capacitors. My Laserjet 4+ needed a full recap a few years ago. I also recently restored an Okidata OL400, which had a few leaking caps on the print engine board, and one on the LCD display.

There's usually a way to make it print a test page. Often the print engine board has a hidden button to print a basic test page. I saw a Next printer many years ago, and it looked like it used the Canon SX (same as the Laserjet II/III), but I could be mistaken.

Assuming you get it to print, you'll probably run into problems with the wiper blade in the toner cartridge. It's made of rubber, and degrades with time. Even new old stock will be bad if it's more than 10-15 years old. Worse yet, the degrading rubber sometimes leaves a permanent mark on the print drum.

Replacements are available for some print engines. I had to modify ones for the Laserjet 4 to fit other printers (like my OL400, and a Canon PC-20 copier).

 

[Al Kossow]

If it is a Canon CX print engine, a bunch of rubber rollers inside have turned to goo.
The paper pickup mechanism and separation rollers are particularly bad.

 

[booboo]

Good poing @andy From the Service Manual: "
Test Print button
The test print button is located behind a
panel on the front side of the . base cover. (See
Figure 3-1.) Pressing it causes the printer to
print the test pattern stored in the memory of
the DC controller PCB.
After the printer has been switched ON by a
signal from the external device and the RDY signal
has been made TRUE by the printer, pressing
the button will cause the printer to print a page
of the test pattern.
If the button is held down, the printer will
print the test pattern continuously."

 

[powerlot]

Hey all, thanks so much for the tips

The first thing to do is closely inspect all the boards for leaking capacitors. The early 90's was prime time for defective capacitors. My Laserjet 4+ needed a full recap a few years ago. I also recently restored an Okidata OL400, which had a few leaking caps on the print engine board, and one on the LCD display.

True, the monitor had some really bad leakage already. I didn't even think of printers having the same issues.

Assuming you get it to print, you'll probably run into problems with the wiper blade in the toner cartridge. It's made of rubber, and degrades with time. Even new old stock will be bad if it's more than 10-15 years old. Worse yet, the degrading rubber sometimes leaves a permanent mark on the print drum.

Replacements are available for some print engines. I had to modify ones for the Laserjet 4 to fit other printers (like my OL400, and a Canon PC-20 copier).

Do I have to take the cartridge apart and fix it? It's a Canon EP-S cartridge so probably any related cartridges for other printers which takes this one should work, no? I'm afraid of getting a new one and finding out the printer is toast, but that would be the cost of the business

If it is a Canon CX print engine, a bunch of rubber rollers inside have turned to goo.
The paper pickup mechanism and separation rollers are particularly bad.

By print engine, you mean the mechanism that takes the cartridges? Is this an OEM type of deal with printers? Stupid questions but I never dealt with printers this complicated before.

Anyway, the rollers on the output tray side look pretty bad. I guess any other rollers are probably trashed too.

If I can identify the print engine, I guess there's someone out there who already restored one, in case I need to do the same?

Good poing @andy From the Service Manual: "
Test Print button
The test print button is located behind a
panel on the front side of the . base cover.

I tried to find some documentation, but without success... this super useful, thanks!

Next steps, taking it apart and see the extent of the damage

 

[njroadfan]

Canon EP-S toner is also used in Canon SX engine printers, as found in the HP LaserJet II and III and the Apple LaserWriter II series. The NeXT likely shares some guts with the SX siblings, their weak point is the pickup rollers, fusers, and the power supplies. Without a parts list for the UX engine, I couldn't tell you if anything from the SX cross references.

 

[powerlot]

Laser printers are complicated

@booboo I noticed that in the attached document contains only the first part. I did some further digging and found the complete document: https://www.nextcomputers.org/NeXTfiles/Docs/Hardware/NeXT_Laser_Printer_N2000/ (it's too large for here).

Unfortunately, still no parts list. It was very helpful with disassembly though, with exception of the high voltage board most components with potentially broken capacitors are out:



I'll go through the boards/PSUs one by one and will check the rubber parts last.

 

[NeXT]

The NeXT printers have been known to have capacitor issues in the DC/DC area since the mid-2000's. At this point you might as well do them and the ones on the digital board as preventative maintenance.

 

[powerlot]

The NeXT printers have been known to have capacitor issues in the DC/DC area since the mid-2000's. At this point you might as well do them and the ones on the digital board as preventative maintenance.

Agree to look at every capacitor in there, some of them on the digital board already show signs of leakage.

 

[njroadfan]

DC-DC power supply was a weak point on ALL of the Canon laser printer engines of the time period (source of the infamous ERROR 50 on HPs). The fuser on the UX engine looks to be different from the SX, so its likely that you would have to rebuild what you have.

 

[powerlot]

Ok, part 1 of the 2023 NeXT printer recappicide tour:

The AC module (pretty beefy with 10A fuse), which contains two electrolytic capacitors:
C152 10uf 50V
C156 22uf 35V

The board had green crust on some component legs and few black spots, most likely from the leaked capacitors.
Both of them were past their due date and read as resistors on an m-tester. As I didn't have the 22uf 35V part I used a 63V rated one, it's probably still miles better than what was in there. I also refreshed the solder on the baked zener diodes.

 

[andy]

You can always go up in capacitor voltage as long as it's not too big to fit.

 

[GiGaBiTe]

Going too high of a voltage can be a problem, because high voltage capacitors have a different internal plate layout that changes their characteristics.

From 35 to 50v generally isn't an issue, but to 63v is when the internal plate layout starts to change. This usually results in substantially different ESR.

If the circuit works, I'd monitor it for awhile to see if anything is getting excessively hot. If you start having weird phantom problems, remember that capacitor, as it may be the culprit.

 

[powerlot]

Going too high of a voltage can be a problem, because high voltage capacitors have a different internal plate layout that changes their characteristics.

From 35 to 50v generally isn't an issue, but to 63v is when the internal plate layout starts to change. This usually results in substantially different ESR.

If the circuit works, I'd monitor it for awhile to see if anything is getting excessively hot. If you start having weird phantom problems, remember that capacitor, as it may be the culprit.

This was one of my concerns with going too high with voltage, but the replacement capacitor was one of the better ones and measured around .6 Ohm ESR. I'll keep in mind though.

I started taking apart one of the other supply boards PS20178E-1, on this one it seems there's mostly (exclusively?) Chemi-Con KME capacitors:
C7 560uf 200V
C8 560uf 200V
C14 22uf 100V
C24 1000uf 35V
C25 1000uf 35V
C27 220uf 10V
C30 1000uf 35V
C34 2200uf 10V
C35 470uf 10V
C37 47uf 35V
C43 470uf 25V
C47 47uf 25V
C48 1uf 50V
C49 0.47uf 50V
C52 47uf 25V
C53 470uf 10V



Not sure I have all of those in stock... I'm also considering not changing the big cans, as I've never seen one of these fail.

 

[powerlot]

Bad news ...

The logic board has had worse cap leakage than I initially thought. Everyone who has one of these printers and didn't look at the logic board capacitors board should do it soon.

R265 was drenched in electrolyte... does anyone know its value or can make out the markings? It measured as 50.25 kOhm, and the markings look like Yellow - White - Red? - Brown? I might replace it but I wanted to make sure I've got the right one.

 

[andy]

If there are actually two white bands, then it's a 49.9k 1% resistor. That would agree with your measurement.

Basically anything made from about 1986-1995 is highly likely to have leaking capacitors. There were a LOT of defective Japanese capacitors made in those years.

 

[Paolo B]

Glad to see I’m not the only one trying to pull off this feat…

Got a unit sold as “junk” and junk was it.
Usual paper jammed message even w/o any paper.
Recapped almost everything, leaking caps everywhere, but to no avail.
Error message changed, but still unable to print.

I am usign the app ”PP” for getting some clue abut what might be wrong, but detected status varies between “Device OK” and “Fatal error”.

I would like to get more details by catching the communication between printer and main unit, but I could not find any documentation (The appendix in the service manual is truncated…).

 

[powerlot]

I am usign the app ”PP” for getting some clue abut what might be wrong, but detected status varies between “Device OK” and “Fatal error”.

Welcome to the forum, also happy to know that there's more people trying to get it running.

Do you mind sharing a link to this app?

I haven't had much time to continue with the recap and I'm missing some parts anyway, so I'm checking some other ongoing projects and low stock parts to order in bulk and save shipping.