The Transformation of Samsung SCX-4200

(This is the English translation of my reader article on Ruuvipenkki)

I bought a Samsung SCX-4200 around five years ago. I was just starting my engineering studies and figured I’d need a printer. Searching around for a suitable candidate, the SCX-4200 popped up. In addition to being a USB-connected laser printer it was also a scanner-copier. I think it cost 160 euros back then, so it was perfect for a poor student. The toner cartridge ran out after a year and in the end I didn’t really need a printer since I could do all my printing for free at school anyway. The scanner has seen twice the action than the printer part ever did.

Little over a year ago I finally decided to get a new toner cartridge. I ended up ordering a cheap knock-off cartridge from Germany but that didn’t end up too well. Read all about it from my blog post from January 2011.

Since I got a better printer (a used HP LaserJet 2300DN) there was no need for the printer part of the Samsung anymore. I did however need a scanner every now and then and yesterday I just decided to start doing something about it. The SCX-4200 had been in the closet for over a year, collecting dust. I took it out and started dismantling it.

Still intact (see the toner seepage in the paper tray)

You can see that the scanner part is “self-contained”, and sits at the top of the device. The gap between the body and the platen deliberate (you can lift it up to allow more prints to accumulate in one go).

The CPU board

The main CPU is an ARM7TDMI called Chorus2. It is, ofcourse, a Samsung-developed unit specifically designed for printer-scanners. It runs at 66 MHz, has 1 megabyte of RAM and 8 megabytes of memory for print/scan jobs. (If you want more details, get the SCX-4200 Service Manual.)

In the picture above, you can see a flat-flex cable and three different cable harnesses. The double-white is the fuser thermistor, so that’s unnecessary. The flat-flex is directly connected to the line camera unit in the scanner. The one behind the flex is scanner motor drive (bipolar stepper) and the red-blue one is the front panel data/power. The front panel communicates via UART at 9600 bps so it is very hacker friendly. It’s not necessarily needed but I connected it anyway.

Toner spillage

As I was rotating the device and unscrewing things the toner was spilling from every nook and cranny. The pirate cartridge had really spewed a lot of toner inside the printer. In case you’ve never encountered laser toner, it is really fine. Like flour but even finer. It stains textiles so be careful.

Main drive assy

As I was disassembling the unit I uncovered a lot of interesting things that can be definitely used again somewhere else. Notice the toner which has covered the gears.

Finally separated

Finally after half an hour or so I managed to separate the scanner unit from the rest of the device.

Inside the printer

Inside the printer is a lot more toner and more salvageable parts. The black flat box on top, that is secured to the piece of steel is the Laser scanner unit as Samsung calls it. This is the thing that actually “draws” the image in the process. It has a polygon mirror inside it and a 0.22 milliwatt laser emitter. (What to do with this thing? Any hack ideas?)

Power supply and logic

Engine assy, sounds fancy eh? That’s what Samsung Service Manual calls the green PCB. Anyway, here’s the other needed bit in addition to the scanner unit. Half of the power supply is redundant since we no longer need -400 V or 1.25 kV but I’ll use it just like this.

Test run

I decided to test the units separately before proceeding. It worked right off the bat. Windows 7 installed all necessary drivers automatically (from Windows Update), which is nice.

The operating panel LCD complains about the door being open and paper tray being empty but the scanner works fine nonetheless. I haven’t had it on for more than 15 minutes at one go so I don’t know if the CPU gets upset about the fuser unit not warming up to temperature. From reading the Service Manual I know that there are error conditions for too low a temperature, overtemperature and something called “open temperature”. These haven’t triggered yet, though. If they do, I might have to fool the unit by adding a resistor over the thermistor connector or something similar. I could get around the door open -error by figuring out which harness has the door limit switch but it’s just a waste of time for no gain.

Finished prototype

We’re nearly there. I took the power supply/logic thing and glued it to the bottom of the scanner unit. Some felt pads were adhered to the bottom. I have no materials/tools to do any better job so this will have to do for now.

This is a perfect opportunity to hone my 3D modeling skills though. Design a housing for the bottom part and have it 3D printed at Shapeways maybe… I’ll see if I ever get to that.

Scanning some PCBs

The scanner works just like before, only now it’s much smaller than before. Yay!

The loot

Here’s all the goodies that were salvaged. A beefy stepper motor with gears, the laser scanner unit (LSU, not pictured here), two solenoids, a round fan, a limit switch and an acrylic “sword”. I’m not quite sure what this sword does, it has grooves that rotate and get closer together. Either it’s an illumination device or it contains a photodiode in the end to capture light. Maybe it’s used in calibration of the LSU?

I call this project a success!

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11 Responses to The Transformation of Samsung SCX-4200

  1. Pingback: Separating a working scanner from its broken printer - Hack a Day

  2. simplifyIT says:

    the sword is used in conjuncion with the OPC on the toner cart in the whole charge discharge process. it is a fairly ordinary LED. dont forget the thermistor and halogen lamp from the fuser unit. or the fuser unit as a whole. perhaps you could make a hardcore laminator….

  3. Pingback: Separating a working scanner from its broken printer « Hackaday « Cool Internet Projects

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  5. Joe Nobody says:

    Is the stepper motor beefy enough to power a compact aluminum can crusher? Perhaps with the proper gearing? As for the laser, sharks in a moat come to mind.

    • Mikko says:

      Crushing cans sounds interesting but there’s not much use for it here in Finland. We get money back from each returned can that is in good condition so I wouldn’t want to crush them. :-P

      Sharks with friggin’ lazerz!

  6. The Axe says:

    Sorry? You get paid for good condition cans which take up a lot of space and you don’t get paid as much for a crushed can that takes up minimal space. In terms of recyclying a crushed can is better as there is less air to transport and more can be packed into the garbage truck.

    Back on topic, I’ve repaired a number of printers by taking the apart and finding the broken bit. Never thought to leave them dismantle though! :-)

    • Mikko says:

      Funny, isn’t it? They only pay you if the can is completely intact, and not crushed. If you bring crushed cans to recycling machines, they reject them. All cans, that are in the recycling program, you pay 0,20 EUR when you buy them. The recycling machine reads the barcode and reimburses you. If they can’t read the EAN code, they can’t reimburse you.

      • The Axe says:

        Ahh, a deposit scheme to encourage you to return cans. Now I understand.

        The UK used to have a similar scheme for bottles in the 70s.

        We put our crushed cans into the weekly garbage collection along with paper/cardboard and glass etc. We have to seperate them all out into different bins before they get collected. Some councils seperate everything, our council only keeps paper/cardboard seperate from metal/glass.

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