Thread by @paulrickards

Welcoming a new (old) printer (back) into my fleet: a LaserWriter II. It’s a workhorse of a printer from 1988 dressed in Snow White design language. #RetroComputing

I had one just like it for years that I used almost daily but jettisoned it some time ago. This one comes to me thanks to @compu_85! You can see here where he was repairing a series of these a few weeks ago.

https://twitter.com/compu_85/status/1543623218652659717

This one has a IIg board in it which sports a ‘030 processor, up to 32MB RAM, LocalTalk, EtherTalk, RS-232, and SCSI. Here’s the first test page that “Web of Fate” printed. Page counter got reset— oops. I’ve got a WiFi232 plugged in to make it “wireless.” #RetroComputing

Output needs some help. There’s a repeating black horizont stripe about 3.75” apart (toner drum issue likely). Since opening it several times, it’s developed a curious blank vertical stripe down the page on everything it prints. #RetroComputing

The LaserWriter II has developed an error around the fuser temperature. I think it’s same as the LaserJet Error 50. I got it working yesterday for about 8 hours by waiting over a day before I powered it on. No such luck today.

I started looking into the fuser and @orion3311 suggested checking the thermistor for a toner clog. It was a little dirty so I cleaned it with some acetone and IPA. Didn’t resolve the issue, still blinks red.

Next I pulled the AC power module. There’s a capacitor on the board that is known to leak but @compu_85 replaced it a few weeks ago. Maybe it’s bad already? There’s signs of a leaky cap but nothing bad. #RetroComputing

I pulled two caps off the board (22uF 25v and 10uF 50v) and they both tested fairly close the advertised values. Unfortunately I don’t have a spare triac so I have one of those inbound.

New triac for the Laserwriter II has arrived. I’m getting very fast at tearing this thing apart for the AC power block 😅 ##RetroComputing

Old triac came out cleanly with some flux and braid. New one in place. Power on and after a couple of minutes the two error LEDs come on again 😣 What’s next? #RetroComputing

Troubleshooting through the HP Service Manual. The thermistor at room temp should be around 1.13 Mohms and I get 0.954 Mohms at 81 F. Seems close enough? Thermoprotector/bulb have continuity (I can see it light and it does get warm). It turns on once but doesn’t turn on again.

Ok this is strange but I just got it to power up and print two test pages. I powered in on briefly, watching the bulb inside. When it went out, I powered it off and quickly pulled the fuser. (1/2)

I measured continuity of the bulb to see if the thermoprotector was engaging. It was closed. I reinstalled the already pre-warmed fuser and powered on again. The bulb lit again, briefly. This time it worked (green LED, no red LEDs)! What’s going on here? (2/2) #RetroComputing

Figured out the cause of the vertical white stripe: an errant screw stuck inside the laser aperture of the toner cartridge! It blocked the laser from charging that area for toner 😅 No idea where it came from! #RetroComputing

TIL Postscript has an interactive interpreter (aka “executive”) in the LaserWriter II over RS-232. #RetroComputing

Used the Apple LaserWriter Utility to set the serial port to 57600 baud with hardware handshaking. Also printed a complete configuration page. #RetroComputing