Samsung ML-1640 printer
For our business we need to print quite a lot of black text on a white background, and this is why after owning inkjet printers in the past, I bought a laser printer. The Samsung ML-1640 was very low cost, and seemed ideal a couple of years back when we bought it.
So far as print quality and speed for the price are concerned, I think the printer is very good.
Sadly, like many products, this one is flawed. Samsung used some horrible techniques to stop you from refilling toner cartridges or using third party cartridges. I find this quite inexcuseable. Luckily, because we use Linux we never had the opportunity to let the printer upgrade its firmware which have resulted in refills no longer working - so for us they do.
Inside the printer
Removing the back cover of the printer reveals the yellow switched mode power supply board on the left and the green processor board on the right.
Note that you should never remove the cover unless you know how to protect yourself from shocks. Never remove the cover when the printer is plugged in as the power supply board is live and note that capacitors on the board can store very high voltages even when the printer is switched off and disconnected from the mains supply.
Do not do this work yourself unless you are confident of your ability to protect yourself from shock. This website provides information but I am not responsible for your actions.
Red light stuck on
After a couple of years of reliable usage, on one day in August 2012, the printer simply stopped working at the end of a print job. It was stuck with the red light on and nothing happened when we opened up the front door, the top door inserted or removed paper. The printer appeared to have turned itself into a paperweight.
I decided to investigate and found that the cause was simply that the top opening door had deformed with heat. The result of this was that a switch on the power supply board which disconnects the high voltage the heater when the door open, was never closing so the printer simply didn't work at all.
A little pressure on the top of the printer in the right place would make the red light go out and allow printing. However, obviously I don't want to have to lean on the printer each time I want to use it.
A permanent fix is easy to do - just bend the metal part of the microswitch a little so that the switch is closed when the door is closed.
Note that this is a safety critical switch. It removes a high voltage supply to the heater when the top is opened. Do not bend the switch so far that it is always on - it must switch off when the top is opened.
Thus far no other problems have arisen with my Samsung printer. If I do have any problems I shall document them here, including a fix if I have one.
I sell bicycle components and lead cycle tours for a living.