EEVblog #303 - Photocopier Extreme Teardown

[mikeselectricstuff]

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!

[IanB]

You could probably use the high voltage board attached to a wire grid to make an electrostatic dust precipitator.

[hans]

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..

[SeanB]

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.

[T4P]

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..

... heh 50mW green laser just next to me

[PeteInTexas]

Really nice! Inkjet printers are so boring btw...

Alexander.

Indeed.  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.

[PeteInTexas]

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?

[T4P]

Really nice! Inkjet printers are so boring btw...

Alexander.

Indeed.  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.

Something 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

[JoannaK]

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.

[nitro2k01]

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.)

The 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.

Ah. 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.

[SeanB]

Here is a pic of a copier imager from an old fax i reduced to produce. Shows the line sensor inside.

[samarkh]

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.

[opablo]

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

[divelectservices]

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.

[SeanB]

Have a look at the laser printer service manuals here....

www.feedroller.com/store/hp_manuals.php

I 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.

[T4P]

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. 

What the heck... Panasonic says it's a IMAGING SYSTEM (aka Photocopier!)
It's not as slow as normal multifunction laser printers!

[scottwolf369]

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