Weird Color TV problem -- colorless!

Factual Questions
1

We inherited a relatively old Mitsubishi color TV from my wife’s grandmother; it’s much bigger than our old one, and we were happy to have it – until the weirdness began. From time to time, and almost all the time lately, the color turns off, leaving us with a black-&-white picture.

I’m no expert on how televisions work, but I do have a biophysics degree, and I do know the basics – the electrons, the magnets, the phosphors, etc. I don’t know much about color TVs specifically, and I’m a little shocked that this problem is even possible. I thought that a TV could lose one color at a time, as an old monitor of mine did, but I didn’t think you could lose all the colors and be left with any picture whatsoever.

So, I have two questions: (1) How does this TV work? and (2) Can this be fixed?

2

Color TVs use a HLS (hue, lightness, saturation) color model.

The lightness information is usually called the luminance signal, and this was all that was transmitted before the advent of color TV.

The hue and saturation information is conveyed in a separate signal, called the chrominance. A monochrome TV will ignore this signal altogether.

If the circuitry in a color TV that decodes the chrominance information is disabled, the TV will function as a monochrome TV.

3

Also a TV will sometimes display a black and white image when not quite tuned properly.

4

Yes, check the tuning. You should just be able to change the channel on the TV up one and back down. This will cause the tuner to reseek the channel.

If that doesn’t fix it, the problem can probably be repaired inexpensively. As a repair shop to look into it. You could be getting a several hundred dollar TV for the cost of an easy repair.

5

I have an S-Video A/B switch (I guess C & D also…it has 4 inputs) to route various things to my TV. Sometimes I get the Black And White syndrome. Jiggling the switch on the input will make it come bac color. I don’t know if you have S Video, but it might be a loose S Video plug. Other than the tuner, I’ve never seen this with composite video. Just a thought…

6

If there is something wrong with an electronic component, then there is no way on earth it can be economically repaired by a pro. Doesn’t matter if it’s a 1 cent part, the tech will charge you Big Money for just taking the cover off. Any such repair will be well past the value of the set. You have to hope it is a mechnical problem. A loose/corroded connection/switch, etc. Just don’t take the cover off, even if it’s unplugged. Be There Dragons.

Here’s some info on such problems, but it is geared for very knowledgable techie people. The warning on DIY work on TVs should be followed.

7

Well, I tried the tuner trick, and no dice; the color flickers on and off as before. I should also mention that sometimes, the color comes on oversaturated (but never for long). It’s definitely looking like an electronics problem, and one that a competent electronics tech could fix, but I’m not a competent electronics tech, and I don’t know one who works cheap. I guess we’re buying a new TV.

Thanks very much for your input – it makes me feel that I’m making an informed decision, even if the TV isn’t getting fixed.

8

What’s the source of your TV signal… cable, set top box, or antenna?

I use an antenna, and the poorly-tuned stations often show up in B&W. (And there are always poorly-tuned stations. When I move the antenna to clear up channel 2, channel 28 gets worse. If I turn up the amplifier to help a weak channel, another becomes too strong.)

9

Digital cable w/ set-top box.