Featured image of post Televideo 925 Keyboard Conversion

Televideo 925 Keyboard Conversion

I bought a bunch of Televideo keyboards and converted them to USB

Introduction

A lot has happened since I last posted here several months ago.

Keyboard-wise, I’ve gotten very much into learning more about designing and building converters. This prompted me to order about 40 Televideo 925-style keyboards from elecplus with the goal of converting and reselling them.

Televideo Keyboards Organized

Fixing these up turned out to be a TON of work but quite a bit of fun as well. I wanted to share a bit about the process I’ve been taking each board through. Usually I’m doing a few at a time, grouping like boards together.

Before:

Keyboard Before Photo

Keyboard PCB

Keyboard PCB Top

Step 1: Map out PCB

Using a multimeter set to continuity check mode to check which pins correspond to the rows and columns. I mark the pins with a permanent marker.

Sharpie Markers

Step 2: Remove keycaps

Space invaders can be a little bit tricky to remove the caps. I use a sideways prying motion to pop them off.

Step 3: Remove unnecessary components

Removed all of the unnecessary passive components like resistors which can pull the signal down and give weird key presses.

Step 4: Desolder ICs

Since we’re replacing the controller, these aren’t needed any longer

Step 5: Dust the life out of it

This thing is awesome. So much better than canned air and it’s paid for itself several times over

Step 6: Clean the keycaps

Keycap Cleaning

First I soak them with dish soap then run them through an ultrasonic jewelry cleaner a few times.

Step 7: Clean the case

Big Plastic Container

Dirty Keyboard Case

I use a mr clean magic eraser which gets off all of the marks with minimal elbow grease

Step 8: Solder pins onto teensy

I use a breadboard to keep things in place while I solder the pins.

Teensy Microcontroller

Step 9: Solder teensy to board

Thought about socketing it but my pins were a bit too fat to fit.

Step 10: Replace keycaps

Luckily I have lots of boards to use as a reference.

Step 11: Test matrix

Just making sure everything was traced out correctly.

Step 12: Map matrix

I have a little arduino sketch I wrote which prints the row and column for each key. Makes this job a lot easier

Step 13: Program TMK

I love TMK! Looks tricky but it’s fairly straight forward once you’ve done it a couple times.

Step 14: LED

Forgot about the LED so I had to do it after the fact.

Step 15: Compile and flash

Fingers crossed…. IT COMPILES!!!!!

After:

Keyboard After Photo

Update 1/28/2022

I recently did a photogrammetry scan of this keyboard.

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