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Was an intern for Lexmark (who made Dell printers for at least a while). The drums are charged up with a roller, discharged to ground by the laser, then pick up toner electrostatically where still charged. The toner is then transferred electrostatically to the plastic transfer belt, which is later transferred to the paper electrostatically. They use the belt so the colors register with one another; that can't be done well enough by transferring each color to paper independently. Getting the belt to track well on the rollers is quite complicated, and I believe was done mechanically with linkages and springs to steer it passively Voltages are on the order of 0.8-3kV. The process is very sensitive to environmental conditions (humidity, etc) and paper type. The engineering effort is tremendous. There is probably an output paperpath team. I sat in on some meetings where they were doing explicit dynamic FEA (very computation intensive) of the transfer belt because of some issues they were having that required an extremely good model of friction. I collected some data to validate photoconductivity FEA models (among other things). People maintain tables of the circumference of all of the rollers so if they have a periodic print defect, you can trace back which roller it's coming from.

The people that design highly complex machines like that, are geniuses.

I always found it funny that people get so impressed seeing a 3d printer work, while it only has 3 stepper motors and a heated extruder in it. At the same time, these people own laser printers themselves and are mostly pissed at how crappy their printers are.

I started working on these back in 1981 ... I'm studied electronics tech in college ( EET ) shortly after returning from Sydney, Australia (2 years LDS Mission) I answered a help wanted ad and have doing it ever since. Started my own copier printer business 28 years ago and am pretty much retired now. I started with black and white liquid toned copiers, then went on to dry toned machines, then machines with Document feeders and sorters, then came Fax machines ... Roll coated paper, then plain paper, then scanning. as technology moved forward ... the amount and size of parts shrank, motors were driven both directions and one way clutches enabled one motor to have 2 functions, magnetic clutches and one way clutches brought down the part count ... the electronic complexity increased exponentially. Customers used to use a Copier, a Fax Machine, a Printer, and a Scanner ... then someone thought to combine them all into one unit !! the only problem with that was that a simple paper jam brought the whole office down. It's been an interesting career and I've always said that someday I'll write a book about it !! As a side note ... many of these machines aren't even made by the people whose name is on the front ... same goes for most consumer electronics. The parts are sourced from all over the world and parts from one machine sometimes were the same as another machine, ex: Canon built HP printers, Lexmark used to be Toshiba, Dell was made by Lexmark. who got the machine from Toshiba ... Savin, Gestetner, Nashuatec are all built by Ricoh. Xerox hasn't built anything for years, they have put their name on machines from Sharp, Toshiba and Samsung ... As I hear it in the industry, HP bought Samsung's printer business, Xerox has tried to buy HP ....... the reason toner is expensive is because of the chip that the manufactures put on the cartridge, trying to keep you from using third part Ink / Toner ... HP used the same black toner from the old HP2's for many. many years ! ( It's been an interesting ride ) I get a kick out of how excited you get over an old copier or printer ... I watch a lot of your videos ... interesting to see what makes something work ... everything we use today started out with a copier that relied on a big motor, chains, gears, relays, micro switches, Heat lamps and Semi-conductive image drums. Keep up the good work ... enjoy your videos !! Mike

The light pipe at 15:10 is used to erase the previous residual image before the next image is scanned onto the drum via the laser.

Output paper path guy is not happy you called him a team.

The disadvantage of parting out such a thing is that you are left with 5 times as much trash as you started with! You get the couple of parts that are interesting and put them in the parts boxes but now you have a car trunk full of trash to haul away to the recycling center :-(

"Thank you for repairing the printer. You have golden hands. " "My hands are CMYK at the moment."

I remember the first laser printer I ripped apart for the stepper motor parts, that was when I was first getting into tinkering with electronics! Now I have a closet full of them.... and I had to get shelves to hold all the small form-factor PCs... I can stop anytime I want though!

"No, really usable parts.." in the laser unit? Dave, these surface mirrors are one of the best parts in that printer.

The mechanical parts were designed by Cogswell Cogs, in competition with Spacely Sprockets.

High voltage board salvage the high voltage resistors out of there, as they are useful to build a DIY high voltage probe, using the 2kv rated resistors.

22:28 those gears with the helical ramps; the ramps are slipper clutches. Since steppers are known for producing large amounts of torque, you need a passive means of torque limiting so they don't strip the gears if there is a jam. There is likely springs that push on one side of the gears to provide preload on the helix and give the right amount of overload tension. The helix angle will match the helical gear angle so it cams out at the same gear timing angle so there is no advance or retard as it cams out.

I was a repair guy on the Dell 5100CN printers. and i still use one, those toner cartridges, i got about 30 news ones. those printers will print edge to edge on both sides at about 2 seconds per page. to bad you trashed it, a clean up and those lines would have gone away.

I like how you put the blue tarp out like you're dismembering a body.

Printer tech and trainer from Xerox here, that black linkage @08:00 is a mechanism to disconnect the drive of the colour drums. The colour drums are not driven during B/W printing, extending the life of the drums a bit. The toner supply is controlled with a toner concentration sensor in the drum / developer cartridge. If the sensor sees that there is little toner in the developer, the stepper motors of the cartridges are turned on for a few seconds (2 seconds for this machine). The fresh toner is dispensed in the developer, and mixed in with the developer material. The plastic rod and LED are part of the drum eraser system, It makes the drum electrically neutral and erases the electrostatic residue of the drum. The green stuff on the drum is a photo sensitive layer, so getting rid of electrostatic charge is easy, just shine a light on it. If you have any other questions, let me know

Those gears with the ramps obviously allow travel in one direction only so perhaps they allow you to pull the paper out without breaking the geartrain.

FYI on cleaning all that horrid toner powder off your hands - use cold water and lots of soap. Hot water will start the setting process and make it harder to clean off :-)

These are stellar for fabricators, too, not only electronics people. Especially the multitude of high quality shafts, those things are priceless.

I'm just glad that I'm not the only one with a bin of scrapped PCB's and another bin of scrapped motors, power supplies, connectors, etc.

"Whats worse than a paper jam?" "Falling off a cliff" "Being sucked into a black hole" Cant argue with that :)

That printer is from the 26th of August 2013. I would expect it to be in service for much longer than 6-7 years. Guess someone needed an upgrade

We used to have one of these printers in my office. Great for printing training material and manuals. I sure do miss it now!

6:24 give Dave some privacy, he wants to be alone with his motor

Love it! Already as a kid i had a look inside electronics peopled throwed away. Always fascinating! Thanks for your professional look inside!

These things were $1549 (US) brand new. That was ten years ago though, so I suppose the company probably got their money's worth out of it.

You're the only youtube channel that could ever make anyone physically want a dumpster room

I have done this for years and have a shed full of parts that eventually will end up in the dumpster...totally worth the time and effort. Cheap thrills! Front surface mirrors are good for kaleidoscopes.

Sounds like you're calling a horse race when talking about the PSU towards the end. Classic Dave Teardown Excitement lol 😁

I love scrapping old equipment for parts. I try to keep motors and gear trains in tact. Lasers, mirrors and lenses are pretty cool too. All the screws, nuts and other hardware can come in handy as well. Nice find.

I think that light pipe is a quenching lamp. It just eliminates any residual charge on the drum. The older ones used fluorescent tubes

Mmm mmm, lots of stepper motor goodness. The engineering in these devices is amazing. I always wonder how many model iterations there are over the years using the same "guts", with cosmetic changes.

always a treat to watch, especially seeing the laser mirror optics first time.

9:57"...mold afficionados..."!!! SUBSCRIBED!!!

Cute boys, “a thousand or more”. It is incredible how much volume was stuffed into the case of that printer.

you will spend as much time cleaning up as you did taking it apart. Thanks Dave, and those of you who left comments, it was fun to read.

Classic teardown! Other very useful parts are the steel shafts from the paper feed path - I remember our late friend Aussie50 tearing a copier down and finding those quite useful.

You're like the Steve Irwin of electronics it's great, you get so excited about everything

What's worse than a paper jam? A paper cut!

I worked as a laser printer repair tech for 4 years in college.. Every day was replacing bushings, gears, and little sensors broken from paper james... fun stuff.

Your smallest kid walking with his hands on his back reminds me to my grandfather 😢

Good morning. Dave again :) Can't sleep so I watch EEVblog. Greetings from Austria

RGB adds up to white. CMY adds up to black. if you shine torches with filters onto a wall it shows up additive vs subtractive color easily. It's very interesting for the history of color photography and darkroom printing processes (before this ink and toner based plotters did it better and faster).

What a grandpa. An engineer and a youtuber. i wish i had a grandpa like you yet i never met my grandpas as they were long gone from this world when i arrived.

I saved a Dell 4C laser printer from being trashed by my company just because it refused to work with a message saying that the belt's official lifetime was exceeded (100,004 pages printed!). I was not going to accept that. Took me some studying of the really excellent service documentation (it turned out the printer was really a rebranded Xerox) to find that there were two signals going to the drum that were called SDA and SCK - without further explanation what the obvious I²C was used for. :) I then only needed to reprogram the drum's lifetime value in its EEPROM - and the printer booted up fine, and the printing quality is still amazing! These business printers are really a gem of engineering and documentation. Hats off!

As a kid we would go to the dumps with a cardboard box and wire cutters, remove the resistors and capacitors from TV sets. I still have some of those parts laying around somewhere. You run out of room storing junk.

The lines you get on that stuff Dave, is dirty mirrors. When I was in the Military and a computer, Telephone tech, I had to take printers a part all the time and clean the mirror off and it was good as new.

and the microchips don't actually monitor physical toner level, they are simply eeprom devices that register if the toner was used, and decrements the "full" to "empty" count. You'd be surprised how much toner actually remains in an "empty" cartridge.

That power supply was a bloody rippa mate. The motors, mirrors and lasers were a keeper also. Yet another quality tear down.

Recently been to a company that makes letter folding machines. Eventhough they are mostly made of metal, it looks similary complex. An amazing piece of engineering

Had a smile when you mentioned laser art! :)

After seeing your photocopier video ages ago, I actually brought a second hand office photocopier for £20 and I am pretty sure I got 10x that value out of it just in motors. Since it was early in my electronics days it was also a tremendous wealth of caps, resistors and wires for prototyping. Was more than worth the money I paid for it.

I know this sounds bad or like me saying that everyone in Australia is the same but I mean it as a compliment when I say you have the same energy as Steve Erwin one of my childhood heros.

Who is getting Goosebumbs too when he goes through the Laser Assembly

The big brown belt is the transfer belt. The image is built up on it by static from each of the 4 drums. then the foam transfer roller statically charges the paper to transfer the image to the paper. Finally the fuser melts the toner into the paper

Joy forever, another good video Dave you had me in stiches with Ken Done, Beudiful!

I was their age when my dad brought home a junk royal copy machine. My sister and i took it apart on the lawn. We ended up with gear motors, fans, Coronas, chains, fancy lenses, and we got covered in toner. it was the early 80s and toner came in a bottle and didn't stay in the cartridge when we took it apart.

13:43. HAHAHA!!! This is my same rebuttal when people say "Worse case scenario". Smart kids!

Friday afternoon entertainment at its finest

The complexity of this thing is insane....I have a new respect for printers

My Brother HL=2140 has been really reliable too. It is only a black and white laser I must have had for more than 7 or 8 years but it has never given me any trouble, other than just ONE paper jam. I have only replaced the toner twice and one of those was that underfilled starter cartridge a lot of printers sometimes come with. It never needed a new drum and still prints like the day we first brought it home. One time I had a problem with dirty looking prints but that was easily fixed by separating the drum and toner cartridges. All I had to do was take it outside and carefully blow the loose toner out of the drum assembly. Now it prints like new again. I once had an Epson Stylus color 200 but that thing kept getting clogged nozzles and wanting new cartridges much too soon. I threw it away!! It is a shame too because it printed much better photos than some of those dedicated photo printers. I had a portable photo printer and it didn't print as sharply and nicely as the Epson did. Still though, I was tired of inkjets and threw the thing away. I never had a printer that was so unreliable. Laser printers are the way to go. Sometimes they can be very expensive but hopefully those ones will last longer than you.

Love the ref to Con the fruitier 28:28 Beautiful Coupla day's! Miss those old skool shows.

The day i found out my school's laser printers used the same SDRAM as my PC was an amazing day. Especially when I found out the printers continued working after I had pinched the RAM!

I would have done the same thing minus knowing wtf I was looking at. That's why I love this channel.

The people that design this stuff must be from another planet. Where does one begin?

Also a great source of 4mm screws (unfortunately only a few nuts). If you buy a box of 4mm nuts these screws can be used for Meccano screws.

I worked night shift at a NOC for 17 years. Used to fill trash cans all over the office with parts I took off old printers and PCs. Kept all the steppers and steel rods. Sold em by the pound!

Hux is really energetic! Knock of the ole block I'd say.. soon to be seen with Dad on the next canyon run?

@ 22:40 : nope Dave, except if it's wrote on, it's not an average DC motor but a 3-phased motor (like spinning motor from disk burner/reader or HDD) One of my engineer friends say that's accurate enough for know position (and that's why it's used in these devices) But still keep it (with the power supply board come from printer, high probability that's got +5V/+12V also)

Wow, yards and yards of high quality fine stranded hookup wire to be salvaged out of that!! Thats worth the price of admission right there!

That big flat belt that wouldn't come out at 9:11 is the image tranfer belt. You have to lift the blue handles to pull it out all the way. What happens is each of the 4 drums lays down the different color images onto the belt. When the image is complete, then the belt makes another rotation as the paper passes under it, thereby transferring the image from the belt onto the paper. That is why it is called the transfer belt. This makes the giant printer slow because the belt has to make 2 passes for the image to end up on the paper. So the unwanted line could come from this belt also because there is a cleaning blade that cleans the belt. If the belt is not clean, then you end up with ghost image from the previous print or lines. Drums and fuser roller (heat rollers) can introduce lines too. The more modern color printers deposits the toner straight from the drum to the paper which makes it faster and reduce one less source that can introduce a line on the print! The light pipe at 15:16 is for discharging the drum. It effectively erases the drum so that it is ready to receive another image from the laser. Often when someone worked on a color printer, they end up with psychedelic boogers because they breathed in some of the color toner! 😂

Maybe have a video showing how to make those motors work (the scanning one for instance)? As a hobbyist that have one but with no idea how to make it spin. I would appreciate it.

Dave. Your kid growing up fast man 😂💙💙

The mirrors are useful for anyone who plays with lasers as they are good quality front surface reflecting. I have a box of bits from laser printers and old barcode scanners from work which I use bits from for laser light show projects.

Dude, this video is beyond awesome!

That laser assembly has a bunch of beautiful first surface mirrors and optics, you can do nice things with them, get two of the scanner motors and a visible light laser (the ones in there are usually IR) you can project lissajous figures

The complexity is also reflected greatly in the accompanying drivers

I would like to see Dave design something with those salvaged components/parts to show what is possible. I appreciate there are a million and one ideas but I would be interested to see a video on the design and build.

That switch at the back is an interlock for the rear cover. Will throw a ros fault code if its not actuated

that model is long discontinued, but when it was new in 2010, is started at $1500 USD for the base unit, and went up from there with multiple paper handling units,,and "finishers" ie collators, binders, etc

Nice! I did the same a few month ago on a massive Samsung printer I found on the roadside. It was a rather recent model but replacement toner cartridges are like $ 150...

23:53 there is description of the connector so it’s easy to use it. Usually it’s step/dir drive.

The ridges on the light pipe direct some light down and out of the pipe. Much like a lenticular grid or Fresnel lens.

I think I mentioned this under the dublidoo for a cash register teardown, but to me the most amazing enginerding aspect of these devices is the thermals. With a laser printer, you need to put enough heat onto the drum to hold the toner to be transferred to the paper, but dissipate all that heat before the drum is written for the next page...with a resolution of hundreds of DPI and a throughput of several pages per second. All the mechanical enginerding isn't much more impressive to me than an automobile.

I would think the light pipe is used to clear the drum between pages (or maybe more periodically). Much like the laser, but over the entire surface evenly.

If I'm not mistaken, the light from the light pipe likely is use the erase the previous image on the drum or to help the system prepare to clean the residual toner left over. I used to repair copiers many moons ago and have forgotten a lot and I'm sure the technology has improved some as well.

I'm just about to blow up a scanner-printer for parts, this really hits the spot :)

My guess is that the clear plastic tubes next to the drums are a light pipe routing UV from LEDs to erase the drums prior to receiving a new image.

- The image is formed on the transfer belt (9:15) by the individual drums. The printer will occasionally print test patterns on the belt for color synchronization and density correction and scan them with sensors without ever needing to actually print them on paper. You won't know this is happening unless you open the door at the right time in the warmup cycle and see the patterns on the belt. - The paper only ever goes up the right side of the machine and comes out the top. The roller at 8:53 presses paper against the transfer belt at the edge and immediately sends it up the fuser. Or in the case of double sided prints will send the paper around through all that extra plastic in the door to print on the back side. - LED and light channel connected to them are for erasing the drums. They are quite effective and are still widely used in copiers and printers today. Actually, They are used along with the corona charge wires (buried in the drum assembly) to make sure that all areas of the drum are being charged and discharged regularly, not just where the printed areas of the page land. - Many of those 4 pin connectors are only for tracking new consumable items like drums and transfer belt. They connect to a "fuse chip" that blow after the printer acknowledges that a new item has been installed. It will reset the page counter for that item then command the chip to blow. Many would think this is a money-making technique, which it sort-of is as you cannot take that item out and install in another printer and have it think it's new. But more importantly the machine will compensate for gradual wear by adjusting voltages etc. which you want reset when you install new items. The Transfer Belt has one of these chips on the back side as seen in 9:39. I do service on these style machines as well as color photocopiers (not dells/lexmarks)

Why am I watching this, I should be asleep for hours now. Anyway, great video! ;)

Apart from the image illumination of the drum by the laser, there is also an erase lamp to delete the image before next cycle. That might have been that light pipe with the diffuser prisms cut into it.

I was the poor bastard who had to swap out those boards at IBM. Lol.

Honestly, I would keep the PSU as it is. I usually keep them (especially smaller ones). You never know when you'll need a multiple output PSU!

Buying a color laser was one of the best decisions ever, am on my third set of toner in 10 years, and there's no drying out if I'm not using it for a few weeks or even months. And it's often cheaper to buy even more expensive replacement parts, since the cost over time is so cheap. (Of course, third party toner is the way to go)

Nice blast from the past with Con the Fruiterer!

I am a printer repair tech. I could explain how the process works. The printer is not very smart, it doses each print job the same amount of toner. Using sensors, it reads the concentration of toner in the developer and discharges after so many prints. This is depending on how accurate you want your printer to stay. This guy is going good at explaining a printer.

World first! I'm pretty sure no one has ever described a Dell printer as "high end" before, lol

19:00 You should take a laser pointer, aim it where the emitter would shine, and spin the scanning prism. I hypothesize you would see the beam scan across one of those mirrors and it would be really cool b-roll video or a separate quick demo.

Love my Nidec fans, dell uses them a lot they're great

Old buddy worked at IBM's main office in the late 80's to the early 90's and he used to joke about the corporate song book and having to learn the songs.