Thread: Idiot box problems

Originally Posted by patty

I was interested to see if anyone out there hasany ideas on repairs of CRT Televisions we have not even had the current television for 2 years yet and the colour has been intermittently coming in then drops out first we lost red,now the screen has a green tinge to it,and lost all colour altogether we still have a picture and everything else seem to be ok I have heard of a degaussing wand that is used to de-magnetise the picture tubes in televisions and monitors that have been to close to other magnetic fields like large speakers, we use to sit our video recorder on top of the TV and I am thinking this may have caused it but am not too sure any ideas would be appreciated.......

First off, sitting the VCR on the Telly didn't cause it. Secondly, and sadly, your TV is properly stuffed and in this day and age it will likely cost more to repair it than a new set. Not much help, but an unfortunate reality.

What Bob said. If it needs degaussing it tends to be a blob of weird colours, often in the corner(s). If you have a small magnet you can see the effect if you move it close to the screen. In a domestic situation a requirement for degaussing is often caused by people switching a vacuum cleaner on/off close to the TV. The set itself has a built in degaussing coil, but sometimes it's not enough.

Don't be tempted to take the back off "for a bit of a look", there are very high voltages in there that will remain even with the set unplugged, also the chassis is live.

Before trashing it just be sure it's not something obvious like the tuning being ever so slightly off, as that will affect the colours.

Thanks guys for your replys television faults and diagnosis repairs are certainly not my strong points and have never had anything to with them I will "play around with the tuner" to see if i can get it going but i seriously doubt it! well it loks like I'm up for a new tv as much as i have been lusting after a nice plasma ever since they hit the market it really is not something i want to be blowing cash on at the moment well it was the Hot water service 2 months ago now the tv is gone i wonder what is next? they say things come in threes dont they!

Thanks again

If the set can display a viable B/W picture when it looses colour, the tube itself and most of the circuitry would be ok.

Standard analogue signal is transmitted as a B/W high res signal, (combination of red, green, blue signals) and two low res colour difference signals (B/W- one of the colours and B/W - another colour signal). This makes the signal compatible with B/W tvs which ignore the colour difference signals, while still allowing the colour sets to recover the individual colour signals.

In a colour TV, white is created by mixing the three colours in appropriate proportions. If you started loosing one colour then another, then dropping to B/W, the problem would most likely be the colour decoder circuit.

If the set is an established brandname product, it should be repairable for much less than replacement cost. However if it was a store brand unit, getting parts, circuit diagrams etc could be difficult, and make repairs impractical.

As has been said above it is probably cactus, but it could be the tuner.
To check if it is a tuner issue use an AV input. Normally this would be via RCA plugs from a DVD, VCR etc.
If you get good pictures here it is the tuner that is faulty. Don't bother to get it fixed just buy a cheap digital receiver and plug it in to the AV socket.

On the other hand if the pictures are still no good, bin it.

Hope that helps.

Be aware that the voltages inside the TV are VERY high. You'll get a much bigger shock than your worst nightmares if you come in contact with that.

Mains 240V is nothing compared to what's on the back of a tube. And that voltage will stay there for a long time even with the TV unplugged.

Keep well away if you don't know how to properly ground the tube or at least avoid contact with the high voltages. I learnt the hard way about this one years ago and it sure does give you a jolt.

Years ago, I had a large German made Sony telly...excellent quality. It started to display symptoms as yours is displaying. The first thing that came to my mind was "dry solder joints".

I took it to the local TV guy who fixed the problem, which was "dry solder joints". It only cost me an hours labour & worth every cent.