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CRT Clock, Part I | Kevin Rye.net - Main

Kevin Rye

Geek Extraordinaire. Yeh, I said it.

CRT Clock, Part I

I've always wanted to make an oscilloscope clock or something similar using a really small CRT. Perhaps input some video with the use of something like the Uzebox ATmega game console.

I found this cool little 5" black and white TV in the garbage the other day.


I though it was tossed because the 12V power supply had gone missing. I plugged one in, but nothing. Thinking that maybe it was due to a broken connector or a bad solder joint, I hot-wired the battery compartment with 12 volts. Still nothing. Seems as though it's dead.


I couldn't open it up since all the screws were totally chewed up. I guess someone else had tried to get into it. Whatever I do with this TV, it's going to end up in a custom enclosure, so the case is not important. I basically just took a pair of cutters and cut the top of the case off.

I'll probably end up stripping most of the non-essential components out; the AM/FM tuner and speaker for example.


I took a peek around and immediately noticed that some of the caps had popped.


Maybe the caps had degraded from age? Unlikely. Even though the date of manufacture on the back says it's from 2004, it's not totally ancient. I have vintage Macs that are 30 years old and the caps are fine. It's more likely that theses caps have suffered from "capacitor plague"; very common in the early 2000s. Hopefully it'll spring back to life after I replace them.

I then liberated the TV from the rest of the enclosure so that I could get to the bottom of the mainboard.


Using some solder wick, I removed the caps.


Dang, those things are in bad shape. Must have made a pretty loud pop when they went. I remember I had a 650W power supply in my Dual Xeon rig pop back in 2004. Those caps went off like a shotgun.


I hopped online and ordered some replacement caps, but they'll take a week to get here.

Since this TV does not have any kind of video input jack, it might be a little tricky trying to "inject" a video signal into the circuitry. If it had a composite video in, I could just hack a Raspberry Pi into it. Just as a test to see if I could do something with an Arduino, I downloaded the Arduino TVout library and got to work. While I wait for the new caps to arrive I'll get to work on some code.

As far as hardware, all I had to do was connect a 1K and 470 ohm resistor to pin 9 and 7, tie them together, and connected them to the center pin on an RCA cable. Ground on the video cable then goes to ground on the Arduino.

So, using the following code….

#include <TVVout.h>

TVout TV;

void setup () {
  TV.start_render( _NTSC );

void loop () {
  TV.clear_screen ();
  TV.print_str (0, 0, "All your TV");
  TV.print_str (0, 10, "are belong");
  TV.print_str (0, 20, "to us!!!");

  TV.delay (60);
…I uploaded it to my Arduino and connected the video cable to my TV.


Boom! TV hacked!


Since I nailed the proof of concept, it was time to start throwing some code together to make some kind of a clock display. I connected my DS3231 breakout to the Arduino and got to work.


About an hour later, I had the time, date, and day of the week onscreen. This just might work!


It still needs some work. I have to adjust the time for 12 hour mode, center the text, and play with the fonts. So far, so good.

About a week later, my new caps arrived.


I soldered them in and applied power to the TV.


Nothing. Nada. Zip. It's totally caput.

I measured a few points on the board where there should be voltage, and it's totally dead. The more I looked, the more it was apparent that I think someone else had their hands in here. First, the screws were all chewed up as if someone opened and closed the unit with the wrong screwdriver. There were three JST connectors on the board that were missing whatever was connected to them. In one case, it was totally removed from the board. It's not as it it's just an unpopulated pad, because there's solder on the trace side of the board. Whatever was there was torn off.

So I guess I'm in the market for a new CRT. I'm going to cut my losses with this one and scour eBay for some goodies.

See this project from start to finish:
CRT Clock, Part I
CRT Clock, Part II
CRT Clock, Part III
CRT Clock, Part IV
CRT Clock Case