I’m back again from the thrift store with another calculator! This is the last calculator guide I will be making:) Anyways, this weird thing is called the “Qualitron 24K”. It’s some sort of mid 70’s calculator made by “Qualitron”. I have not found much of anything on the internet about this hunk of old metal, but it looks cool.

As you can tell, it is currently broken, due to the incredibly annoying non-replaceable 6V lithium cell batteries.

To begin destruction of this already broken calculator, use a Philips head screwdriver to remove the two Philips screws securing the metal backplate in place.

Note that there are two different screw sizes! The large one goes where the label is on the bottom, and the small goes on the top!

After the screws are removed lift the metal backplate off. The green PCB is now visible.

If you noticed the missing batteries, I already opened up this calculator to remove them. (There was lots of battery corrosion everywhere.)

I even cut off the wires connecting to the batteries, since it was so gross and disgusting.

Now, use a flathead screwdriver to unfasten the clips holding the PCB in place. Once two of the four clips are unfastened, pull out the PCB from the calculator.

Be careful with the keyboard wires connecting to the PCB!

Now you can see the VFD (Vacuum Fluorescent Display) in all of its glory:)

The chip powering this calculator appears to be a National Semiconductor MM57134ENW/N microprocessor. Based on the internet, it was also featured in the Sinclair President calculator, made around the same time.