More Laser=More Printer

So on my previous posts about PCB making and toner transfer, I mentioned that some printers simply do not work well with this method. My Laserjet P2015 is one of those printers. It’s been a workhorse for over a decade but it simply won’t dump enough toner onto the page no matter what the settings in the printer are set to.

Figuring I had nothing to lose, I took matters into my own hands. Just a disclaimer: I don’t know shit about laser printing. What I do understand is that the laser is scanned across the image drum in a raster pattern, varying the intensity to create an image.(Much like a CRT I suppose)

Dale Mahalko, CC BY 3.0, via Wikimedia Commons

So, starting with our hypothesis of Moar Lazer=Moar Printer, let’s see what we can do. The laser module is usually a big black box with a warning label on it.

Inside we see a set of optics that look surprisingly similar to the ones on the diagram.

Here is the bit we’re interested in. The laser driver.

Don’t bother looking up that RH4-5444 there’s no datasheet. What we do have is 4 potentiometers hooked up to the lower left pins on that chip. Each pin is hooked up to 2 of those pots in series, one low resistance and one high resistance. These set the laser diode current. The lower the resistance, the higher the current.

How the pots are wired with default values.

Anyway, I turned the pots 1/8 at a time until the image became a little bit darker. Here’s the results:

On the right is the default value of the pots, followed by the laser pots being turned an eighth of a turn, then another eighth. There was a minor improvement with each adjustment, but I didn’t want to break anything. The darkest print came from a new cartridge. As you can see, no amount of modification to the printer will solve an empty toner cartridge!

Here is the twitter thread where I did the experimentation:

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