EEVblog #303 - Photocopier Extreme Teardown - Page 1
Forum section: electronics / general

author: EEVblog
author_rank: Unknown
timestamp: July 03, 2012, 10:30:30 pm
content: Dave.

author: nitro2k01
author_rank: Frequent Contributor
timestamp: July 03, 2012, 11:25:45 pm
content: Interesting. Hats off to the engineers involved in this.A couple of thoughts. You mentioned the green drum would be a semiconductor, perhaps selenium. I'm guessing this drum is used to apply the negative charge to the paper. Why a semiconductor, specifically? I'm guessing any resistive material would do. (I'm assuming the reason you don't charge the paper directly using a metal drum is to get an even static charge over the whole paper or something like that.)About 44:18 or so I'm noticing that the LED board says PbF. Could this mean lead fluoride?

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: July 03, 2012, 11:38:44 pm
content: Quote from: nitro2k01 on July 03, 2012, 11:25:45 pmThe drum needs to be insulating but conduct when exposed to light.It is initially charged by the corona wire, the light then discharges it selectively, the toner is then transferred to the paper electrostatically, usually via a wire behind the paper with the opposite polarity to the drum charge.QuoteLeadFree

author: Mechatrommer
author_rank: Super Contributor
timestamp: July 04, 2012, 01:08:27 am
content: 10.25: helix gear. wormdrive is screw looking gear..26.02: the scale... thats one way how mechanical make "calibration" or "alignment"nothing else to do, so.. just some nitpicking dave. no pun intended.always fun playing with mechanical and learn how the engineers find a balance in the loci.and this one is a good example how mechanical and electrical integrated. i got one photocopier teared down years back, still there in that room. my limitation mostly is in electrical unable me to understand and repair all the stuffs esp how the drum and laser work. felt afraid to even touch the drum.so dave, have you figure out how to re-assemble those things? (i doubt that) or its just one way ticket? i highly believe that.

author: FenderBender
author_rank: Super Contributor
timestamp: July 04, 2012, 02:03:13 am
content: That was one hell of a teardown. Thanks a lot.This is a type of video I'd expect from Mike. Mike, you better watch your back. Dave's after you.

author: jpwack
author_rank: Contributor
timestamp: July 04, 2012, 04:01:35 am
content: Epic!Well, now the (mis)informated guesses: the CCD from the scanning head may be an one-dimensional array, I've seen those in some PCB inspection machines, and for the distance, I guess is uniform across the entire movement of the mirrors (and hence not needing more than one aperture angle and/or focus point)Anyhow, tomorrow I'll look with more respect the photocopier in my work.

author: IanB
author_rank: Super Contributor
timestamp: July 04, 2012, 04:04:50 am
content: If that had been an optical (analogue) copier, there would have been a really big lens assembly in the middle of it. I was hoping to see something like that, but evidently copiers are all digital these days. They are basically a scanner and a laser printer combined in the same case.

author: T4P
author_rank: Super Contributor
timestamp: July 04, 2012, 04:53:03 am
content: The larger something is, the logarithm scale goes up in difficulty of reassemblingI tore down a printer from a few years ago and it was quite the similar (being inkjet but the style is the almost the same)Instead of having a stationary CCD sensor i could not really find the sensor being anywhere ...But tearing down a inkjet is not something you want to do ... it's worse then having toner on your hands! The ink's got everywhere!But yeah the electronics control section in the photocopier with the big QFP packages looks similar to the inkjet i tore downGot to love the fans being used disparingly

author: David_AVD
author_rank: Super Contributor
timestamp: July 04, 2012, 05:01:42 am
content: I've seen a rotating mirror scanning assembly like that when junking a standard laser printer. Printers can certainly provide lots of rollers, motors and gears for experimentation.

author: SeanB
author_rank: Super Contributor
timestamp: July 04, 2012, 05:16:58 am
content: I still have an analogue copier that has been scrapped, still mostly works but is giving regular jams, and spares were discontinued 15 years ago. I should do a teardown on it. The big optics are very useful to use as magnifiers, good coated lenses with low distortion.I wonder if i should tear down the Tektronix Phaser I have. Works perfectly, but the cost of running it is a killer. I can buy a new colour laser complete with spare cartridges just for the cost of one colour wax set. Black wax is free though.

author: T4P
author_rank: Super Contributor
timestamp: July 04, 2012, 09:03:43 am
content: I use a epson LED multifunctionprinter nowadays, this new printer is a beast ... Scanning speed's slow though

author: G7PSK
author_rank: Super Contributor
timestamp: July 04, 2012, 09:27:28 am
content: The optical scanner has a very wide angle lens on it, what photographers call a fish eye lens that is why with the differential movement of the mirror to the light and mirror assembly it does not move itself.

author: steve30
author_rank: Frequent Contributor
timestamp: July 04, 2012, 02:43:52 pm
content: Really good teardown.I've dismantled one or two printers so am familiar with the workings of such machines, but I've never done a photocopier.They really must put some effort into the design, because it is amazing what they will do in terms of copying, enlarging, reducing, duplexing, collating etc..... All so some lazy office worker can do single sided copying and moan when something doesn't go as planned.

author: SeanB
author_rank: Super Contributor
timestamp: July 04, 2012, 03:45:50 pm
content: Yes, the old copiers came with the firmware built in to run a duplexer, multiple source feeders, stapler, collater/decollater, sheet feeder and double sided sheet feeder. You just took off the appropriate cover, screwed the extra on, plugged it in to the existing wiring using the plug already there, turned it on and set a few options, either by programming an EEPROM, or by cutting diodes out of a programming matrix under the keyboard.And all this was done with mostly a single chip micro, either a pukka Z80 and support chips or a Sharp or Toshiba integrated Z80 core that was a single chip solution. A few years ago Sharp engineers made a silicon on glass Z80 CPU, and to prove it was a real Z80 they dusted off an old Z80 mini out of the museum and fired it up with this in place of the CPU.

author: Mechatrommer
author_rank: Super Contributor
timestamp: July 04, 2012, 04:18:45 pm
content: Quote from: daveXXXyou give me as many inkjet as you like, i'll be happy to demolish all of them leaving their motors and gears in my drawer. the good thing about the "ink" is its almost improbable to get it into your lung. just refilling toner, i'll prefer to do it outdoor or hold my breath throughout.

author: railman
author_rank: Contributor
timestamp: July 04, 2012, 04:22:02 pm
content: Oh man that led array would make a nice POV, or bench light

author: rr100
author_rank: Frequent Contributor
timestamp: July 04, 2012, 04:35:39 pm
content: Haven't finished the video yet; I don't know much about those particular parts but a light went up in my head when I saw the "clutch" thingies! They are BRAKES!

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: July 04, 2012, 05:17:52 pm
content: Quote from: railman on July 04, 2012, 04:22:02 pmNo because it isn't addressableQuoteNo because it's probably red, orange or maybe infra-red

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: July 04, 2012, 05:19:00 pm
content: Quote from: rr100 on July 04, 2012, 04:35:39 pmNo they're clutches - they connect or disconnect gears from the shaft

author: SeanB
author_rank: Super Contributor
timestamp: July 04, 2012, 05:40:45 pm
content: Depends on the copier. Modern ones are white light ( colour sensor) or older ones are green.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: July 04, 2012, 06:03:31 pm
content: Quote from: SeanB on July 04, 2012, 05:40:45 pmThat array is not for the scanner - it's to discharge the drum. It will be a longer wavelength as that is what the drum is sensitive to - the laser is typically IR or red.

author: SeanB
author_rank: Super Contributor
timestamp: July 04, 2012, 07:23:42 pm
content: Sorry, was thinking of the CCFL scan lamp. The imager optics are arranged to keep a constant path length even as the scanner traverses the paper. The front silvered mirrors reflect the page width scan strip to an image size that will be viewed by the line scanner in the ceramic package in the imager board. Then it is digitised, stored in memory ( top board, the hard drive was probably removed before the unit was scrapped) and then sent to the IR laser in the laser printer side.There it is used to modulate the brightness of the laser diode, and the light is filtered ( the clear block) and focussed into a narrow collimated beam. This then is reflected off the rotating polygon mirror ( the motor with the 6 sided mirror on the side faces, those are polished and diamond coated optically flat machined flats there) . The mirror runs off 24V, and has both a input tacho signal to control rotation speed ( keeps a really constant speed so that the image on the paper does not have horizontal shifts from line to line) as well as having a output that gives a very narrow pulse at the beginning of the one mirror segment reflecting onto the defined reference point on the output window ( set during assembly of the optical block) so that the PLL in the motor drive controller can generate a dot clock to read out the stored image onto the drum.To write on the paper the unit starts all the motors, runs the developer unit to speed and to a stable locked pll loop and then starts the paper upwards. When the edge of the paper is half a drum revolution away from the developer the stored image is read out line by line, then written by the laser as intensity variations onto the charged drum line by line as the mirror rotates the reflected laser beam across the window ( the 2 lenses are there to provide correction to the beam as the mirror rotates to correct for the sine distortion of the beam at the edges of the window, so that the laser beam moves across the drum outside the window at a constant velocity of travel, instead of having variation between the edges and the centre, this simplifies the electronics considerably ( no doing trig on each pixel to correct for location) as well as making the resolution across the page constant) As the beam reaches the end of the window the next mirror segment is just out of being able to intercept the beam. This will form the next scan line, as the paper will have moved 1/1200 inch up during the last scan line.As scan lines are written onto the charged drum ( it having been first discharged, cleaned by a scraper wiper and then charged by a corona wire to a high voltage) they leak charge away, depending if light has discharged the small insulated photosensitive spots on the drum surface. This leaves a pattern of charged spots on the drum as it rotates around. Next the drum rotates to expose the charged spots to a thin film of toner, which has been charged to a opposite charge, and the charged spots get coated with a thin film of toner, in a pattern made by the developer laser. The drum moves further around and is placed in contact with the paper sheet, and the sheet is charged with a contact and a wire behind the sheet, which attracts the toner particles onto the sheet. The now mostly clean drum rotated further to be discharged and cleaned ready for the next scan line to be written on it. The paper moves further to the fuser, where a silicone impregnated roller is used ( it has a non stick surface) to bond the plastic toner particles to the paper by application of heat and pressure to the paper. It then leaves the fuser and is passed though a static discharger brush to the output tray.The drum actually is used multiple times per page to transfer image, you need a much bigger drum if you want to make an image with only one pass. This is mostly done with colour copiers, where there are 4 toner stations that build up a toner image on a transfer film that is pressed against the paper to transfer a whole page of image at a time. These have a single scraper unit on the transfer drum, which has a big container to store the brown gunge that it gets ( mixture of the 4 toners)As to the fuser, I would guess that this one uses a 500W linear halogen lamp hidden inside the black fuser roller, the red one is a soft silicone foam roller that simply applies pressure. This is used in conjunction with the choke to run the lamp at a controlled low temperature during idle, switching the lamp to full power when you press start, so that it heats up the fuser quickly to operating temperature. Energy saving, and running at lower voltage reduces the stress on the lamp. After a few minutes of idle the lamp is powered down totally and the unit enters deep sleep mode, with only the processors and some of the boards powered ( that is why there are so many optos on the power supply, it can run in 2 modes, full power or low power where most rails are nearly off, with the 5v for the micro being provided by a linear regulator on the heatsink that dissipates a lot of power in full power mode while barely staying in regulation in standby) to supply the network and the keyboard functions.If you look at the manuals for copiers there are a lot of options available. I would guess Dave has not torn down any old laser printers, you find the whole paper path assembly there as well, complete with the IR laser block. i am building a collection of those. Would be nice to use to make a LED line display, but you have to clock the diode at 40mHz to get the full beam resolution out of it unless you slow the motor down from it's normal running speed. Now you know why the first laser printers use 60mHz 6800 processors, as they were about the only things fast enough to build an image as a bitmap in ram, then DMA it out to the laser while still having cycles left over to run the paper path and the motors.If you want a different take look for the Tektronix Phaser series of colour printers. try the 360 and 560 units, very detailed manual and a lot of detail on how they actually work.

author: LaurenceW
author_rank: Frequent Contributor
timestamp: July 04, 2012, 07:34:21 pm
content: There is quite possibly more engineering in this thing than in a CAR of a similar age.One thing about that toner dust - it gets EVERYWHERE. If you get it on your hands, wash with lots of soap and COLD water - hot water may fuse the stuff!Also, DO NOT attempt to vacuum the toner up! It mostly goes STRAIGHT THROUGH any filters in your standard vacuum, and then clogs the motor in no time...On the rare occasions that I have cause to go into my own laser printers, I have used compressed air and worked OUTDOORS to blow any toner dust away from the instrument, and me.

author: firewalker
author_rank: Super Contributor
timestamp: July 04, 2012, 08:17:15 pm
content: Really nice! Inkjet printers are so boring btw...Alexander.

author: hans
author_rank: Super Contributor
timestamp: July 04, 2012, 09:43:01 pm
content: Awesome piece of kit and the engineering involved. As I expected, the optoelectronics separates the printer from being a huge pile of cogs and boards into a sophisticated machine. Really interesting stuff.A separate look on the optical units would be cool, but I (personally) wouldn't try to operate the laser section. Not with the lid off at least or with the right laser goggles. I read around on laser printers and it's probably 5mW - 10mW IR (780-800nm), so that kinda sucks because it's invisible and more than enough to burn stuff.I can imagine what SeanB said, the beam has to be extremely collimated. 300dots/inch makes it 0.1mm per 'pixel'.I believe laser diodes usually aren't that well collimated compared to their gas 'alternatives'. They are lasers in that they multiply light inside, (that's the term laser) , but their viewing angle are at worst 10 degrees. Well that's bare diode, maybe this laser diode already has a tiny lens inside it, so the viewing angle is much smaller.Other than that it are almost like LED's that are extremely sensitive to ESD and other nasty things (reverse polarity).I don't get what Optical filtering you would need, as lasers have a very small light spectrum (like <2nm wide compared to several tenths of a color LED). I only think the lens is so to focus the light very carefully on the rotating mirror.As this is an 'extreme' teardown anyway, disassembling and plowing through all boards would be interesting to see what's involved.Especially the optics.. Lasers usually contain TEC's for temperature stabilization, so it would be interesting to see whether it just got a big heatsink or a TEC (with H-bridge?) as well. Ofcourse, it's only a tiny diode, I may be ehm, blinded , having researched controllers mainly for 3W lasers in my last internship (and for 3W output you do need a TEC).The scanner could well use alinear CCD sensorindeed, the sensor looked very thin compared to it's width. I know they are also used in spectrometers with grating mirrors; the grating material reflects the light where the angle is proportional to the wavelength, so you basically get a rainbow inside. Measure it with a 1D CCD sensor, and whoila, you can scan the optical spectrum.I seeToshiba makes sensor with resolutions up to 10k(wow!), so you can scan up to 2400dpi. Probably not in this model, but really quite cool technology you don't get to see everydayDidn't even know such high resolutions existed, the spectrometer I used had 2048 pixels and was branded as 'top class'. Ah well, probably something to do with spectral sensitivity and noise, because the device used a 16-bits converter to read the data.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: July 04, 2012, 10:22:07 pm
content: Laser diodes are generally not collimated due to very short cavity length - they are however very small point emitters and so can be collimated into a beam with an external lens. Lasers of this type will probably not have a TE cooler, just some heatsinking.5-10mw won't burn anything, but you don't want to look at the collimated beam as there is no blink reflex at IR.I suspect by 'filter' above he means focussing/beamshaping - probably just a mis-translation.Would be fun to try firing up all the various bits, especially the mirror motor as these get up to a pretty high speed- some of these will run standalone with maybe just an enable signal. CCFL in the scanner, and the erase LED bar will probably be nice and bright as well.Bit I bet Dave bottles out of firing up the high voltage board though!

author: IanB
author_rank: Super Contributor
timestamp: July 04, 2012, 10:31:38 pm
content: You could probably use the high voltage board attached to a wire grid to make an electrostatic dust precipitator.

author: hans
author_rank: Super Contributor
timestamp: July 04, 2012, 11:28:39 pm
content: It's true 10mW isn't enough to burn your skin (a tiny 60W LED at half power is though, personal experience), but I more specifically meant to say eyes (10mW is plenty on no eye reflex). IR is quite nasty in that (however, I wouldn't prefer looking/reflexing in a 5 or 10mW green laser anyday!)The HV and motors would be really interesting to see running. So hopefully..

author: SeanB
author_rank: Super Contributor
timestamp: July 05, 2012, 05:10:27 am
content: The HV is around 1.2kV, 6kV and a switched supply of +- 2kV. I have some old HP laser boards with these blocks on them. The filter is mostly to remove the off axis scattering, as the drum will otherwise have a broader spot on it.The laser is only on a heatsink, and has a feedback diode on it as well to control brightness. Invisible IR beam, you would probably want to replace it with a red led to see it, though this will destroy the alignment for precision work, but good enough to just power it and turn the mirror to show the beam moving and being corrected by the output lenses. The HP optical blocks i have seen have another folded optical path in them to get a broad beam in a very thin box.

author: T4P
author_rank: Super Contributor
timestamp: July 05, 2012, 05:23:12 am
content: Quote from: hans on July 04, 2012, 11:28:39 pm... heh 50mW green laser just next to me

author: PeteInTexas
author_rank: Frequent Contributor
timestamp: July 05, 2012, 05:45:42 am
content: Quote from: firewalker on July 04, 2012, 08:17:15 pmIndeed. I tore apart 3 hp injets last week. Completely uneventful. In addition to finally making room in the garage, I was hoping to find heat sinks. There were none. There was an optical encoder thingy That was was the most exciting part. The psc 2110 had a power supply rated at 32V 1.29 A. That might prove useful. Otherwise it was all headed for the recycle bin.

author: PeteInTexas
author_rank: Frequent Contributor
timestamp: July 05, 2012, 05:49:14 am
content: Terminology check: A "tear down" have the intent of putting the device back together with full functionality intact while a "tear apart" does not. What do y'all think?

author: T4P
author_rank: Super Contributor
timestamp: July 05, 2012, 05:57:17 am
content: Quote from: PeteInTexas on July 05, 2012, 05:45:42 amSomething was in my mind already when i tore apart my old printer ... i won't get much useful parts other then motors and etc. stuff

author: JoannaK
author_rank: Frequent Contributor
timestamp: July 05, 2012, 08:25:51 am
content: Wearing black clothes while tearing apart photocopier that has penty of toner flying around? ... well, co do, but be carefull afterwards. It's really hard to see how much of that printer dust you'll be carrying home after the day.Other than that.. Nice video.

author: nitro2k01
author_rank: Frequent Contributor
timestamp: July 05, 2012, 11:24:28 am
content: Quote from: mikeselectricstuff on July 03, 2012, 11:38:44 pmAh. I had the idea of the mechanism ass backwards. I thought the actual drum was used to deposit a static charge to the paper, and then that charge was selectively removed by means of the photoelectric effect.

author: SeanB
author_rank: Super Contributor
timestamp: July 05, 2012, 03:34:46 pm
content: Here is a pic of a copier imager from an old fax i reduced to produce. Shows the line sensor inside.

author: samarkh
author_rank: Contributor
timestamp: July 05, 2012, 09:31:46 pm
content: I have taken a couple of colour lasers apart mainly from HP and the scanning head is a 6 mirrors aligned with the laser/lens assembly to give a good parallel scan. The motor used is a phase locked affair. If used with a function generator its RPM can be pricisely controlled. look up Sanyo LB1870.Yours Simon M.

author: opablo
author_rank: Regular Contributor
timestamp: July 10, 2012, 04:45:57 am
content: Dave, don''t you think that the switching power supply board that you got from that tear down is so well layedout and the components are so well spaced that it would be ideal for a video teaching us about how switching power supplies work ?As with any topic; I know that there''s a lot of info on the net to read from... but nothing compares with one of your teaching videos.It could be difficult to do it on a real switching power supply because it has too many more features...And it could be also difficult to do it on a PC power supply or an external power supply because they are always tightly designed for small footprint...And that board... looks perfect for teaching

author: divelectservices
author_rank: Contributor
timestamp: July 10, 2012, 07:09:48 am
content: Just a few thoughts...IT IS NOT A PHOTOCOPIER!!! It is a multifunction laser printer. It is simply a laser printer with a built in optical page scanner.The small board with the "speaker" is a humidity sensor (some also measure temperature also).The 2 large pc boards on the back of the printer are the DC controller and the formatter. If this model had a hard drive installed it would be on the formatter board. Not all multifunction printers have hard drives.The small wires on the fuser are for the thermistors that regulate the temperature and detect over/under heat conditions.Save the large black metal lens assembly in the optical scanner - they are great for inspecting pc boards, etc!That small white box with the DC motor inside the paper tray is the paper lift motor. It raises one side of the tray so the feed/separation rollers can pull the paper from the tray.

author: SeanB
author_rank: Super Contributor
timestamp: July 14, 2012, 10:34:57 am
content: Have a look at the laser printer service manuals here....www.feedroller.com/store/hp_manuals.phpI downloaded the HP laserjet 6l one ( I have one at home I use so wanted the manual) and it has a nice description of how it works. From pg 63 is a description of the working, but sadly no circuit diagrams, though there are timing diagrams.

author: T4P
author_rank: Super Contributor
timestamp: July 14, 2012, 12:17:10 pm
content: Quote from: divelectservices on July 10, 2012, 07:09:48 amWhat the heck... Panasonic says it's a IMAGING SYSTEM (aka Photocopier!)It's not as slow as normal multifunction laser printers!

author: scottwolf369
author_rank: Newbie
timestamp: July 16, 2012, 11:17:03 pm
content: Tearing down a photocopier (or laser printer) while barefoot. Truly, Dave IS that CRAZY Aussie Bloke.Any time I've ever torn anything apart while barefoot I always step on a screw, a sharp piece of metal, a pointy plastic thing, etc.Kudos Dave, risking tetanus in order to educate us