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.
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 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.
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.
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 after half an hour or so I managed to separate the scanner unit from the rest of the device.
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?)
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.
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.
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.
The scanner works just like before, only now it’s much smaller than before. Yay!
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!