Ever wondered for what you can use the I/O port on your TI-84+?

Well, you could of course use the silver link cable to transmit files to it other than USB, but that port also happens to be a 2.5mm audio jack!

So, you could indeed connect some sound system to it, but wouldn't it be more awesome if that sound system was inside the calculator? This is exactly what this 'ible is for!

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Step 1: Preperation

To be able to build a speaker into your calculator there are a few things you need and that you need:

Speaker (mine was 8 ohm)
Resistor (I used 10k ohm)
Transistor
Switch (advantage if it is a double-switch)
hot-glue
dremel
solder
some wire

Step 2: The Theory

Here you can see the schematic.

For R1 I used 10k ohm but maybe another value works better for you.

The thing is that the signal needs to be amplified because else you wouldn't be able to hear anything at all.

Step 3: Open the Calculator

To open the calculator you need a phillips screwdriver and a very small torx screwdriver.

First you unscrew the backup battery with the phillips screwdriver, then you unscrew the six torx screws at the back.

Next you push a card, like a credit card or something, into the small gap at where the batteries are and pull it towards the front. Repeat on both sides. Now your calculator should open.

Now just work yourself forward unscrewing the six more screws until the PCB is completely separate from the case.

Step 4: Time to Start Soldering

Before you can test well, you'll need to solder your wires to the I/O port. As I only used one speaker I used only the left audio channel.

Step 5: Testing

Unfortunately I forgot to take a picture of this.

You should test the setup with a breadboard first, before you actually grind away any plastic of your calculator.

The switch goes between the signal and the 'input' in the schematic, if your switch switches two wires at the same time you can, in addition, also switch the 6V input.

Step 6: Grind Away Excess Plastic

Now you need to grind away some excess plastic, to make space for the speaker.

Make sure to test if the case still closes or if you have to grind away some more.

After some testing I noticed that I had to cut a hole in there to be able to fit the speaker in.

After you made sure that the speaker fits and that the calculator still closes, hot-glue the the speaker into the case.

Step 7: Add the Switch

Next drill some holes at the side of the case for the switch. Be sure to test if the switch can actually switch, so if the hole is big enough. Next hot-glue the switch in.