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You are here: Experts > Home/Garden > Home Appliances > TV/VCR/Stereo Troubleshooting > kv-2780R
Expert: cleggsan
Date: 9/26/2008
Subject: kv-2780R
Question
my sony 27" has no color..picture very well..
Answer
Many possible causes. Requires a test by a good tech to be sure.
However, most common cause would be color killer circuitry.
Here is small section from Samuel Goldwassar book on tv repair:
http://www.repairfaq.org/sam/tvfaq.htm
"No color - black and white picture
This means absolutely no color - equivalent to a black and white picture. Not even a hint of color.
First, confirm that the source is actually in color - try another channel or input device.
Next, check the settings of the color control - it may have accidentally been turned down. If your TV has some kind of automatic picture mode, try turning if off and adjusting the color control. Try adjusting fine tuning if you have such a control and the problem is with a broadcast or cable transmission.
At this point with a confirmed color signal source, there is a problem with the chroma circuitry.
Note that to the average person, the obvious question becomes: is my color picture tube bad? The answer is a definitive NO. It is virtually impossible for a defective CRT to cause a total loss of color. A defective CRT can cause a lack of a primary color - R, G, or, B or a short between two colors which will mess up the color but is not likely to result in a black and white picture.
Some possibilities in no particular order:
1. Weak signal or defect in tuner/IF causing loss of signal strength.
2. Color killer set too high (internal control) if it has one.
3. Defective part around the chroma chip/circuit. Faulty color oscillator.
4. Bad connections in area of chroma chip/circuit.
5. Defective chroma chip (don't suspect this first just because it is probably very expensive).
A service manual or Sams', DMM, and scope will help greatly in attempting to troubleshoot this unless it is an obvious bad connection. Try prodding the main board around the chroma chip with an insulated tool to see if you can make the color come and go.
I had one set where a $.02 resistor decided to open up causing just this problem - perfect BW picture, no color. Another had a coil with a broken wire."
Maybe these ideas will help you with some of your own troubleshooting procedure. They may be too technical; just let me know your further questions.
Hope this helps. Let me know if you need more help after you have explored above suggestions.
C
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