Television screen is blue?


  #1  
Old 04-22-01, 02:41 PM
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My parents bought a 19 inch color television from a motel who was selling them for 25 dollars.It appears to be around 8-10 years old and says Sentry 2 on the front. When they gave it to us 4 weeks ago the entire screen turned blue but changed to perfect color after being on for a few hours. The television worked great up until about 3 days ago when I moved it into a diferent room. Now the screen is the same blue but will not change back to perfect color no matter how long it is on. What could this be and can it be fixed for under $50.
 
  #2  
Old 04-22-01, 04:10 PM
Smokey
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Good Afternoon, cea:
The Sentry 2 is a Zenith as I recall and at $25, it could well be a boat anchor.

With the screen turning blue (assuming no other color is present), it could be a bad kinescope (picture tube) or it could be a problem in the color amplifiers on the circuit board. In this case, it would most likely be in and around the B-Y (blue minus yellow) amplifier. Another possibility is that a blue screen adjustment control may be the cause. It could just be dirty from dust over the years.

What I would recommend is leaving the set off for 24 hours, unplug it, and take off the back. If there is a large accumulation of dust on the interior, cleaning may help.
Use a soft bristled paint brush to GENTLY loosen the dust while holding a vacuum cleaner hose close to the cleaning area. As the dust loosens, the cleaner will remove it for you. CAUTION: WHEN YOU TURN OFF THE VACUUM CLEANER, MOVE IT AWAY FROM THE SET AS FAR AS YOU CAN. Also note that at the end of 24 hours there should be no dangerous voltages lurking inside the set. If there is a LOT of dust, it is possible the dust is causing circuit board shorting.

On the circuit boards and near the rear of the set, you will find one board that has three small thumbwheel controls. One is red, another green, and another is blue.
These are the adjustments for your color levels on your picture tube. A drop or two of WD-40 on each control, a gentle movement of the control, and PUTTING THE CONTROL BACK EXACTLY WHERE IT WAS IN THE BEGINNING may correct the problem.

If none of this works, the next step is to plug in the set and turn it one WITH THE BACK REMOVED. CAUTION: DANGEROUS VOLTAGES EXIST WHEN THE SET IS ON AND I HAVE THE SCARS TO PROVE IT.
Use a wooden or plastic "wand" and gently tap the glass neck on the picture tube. AGAIN, CAUTION: THE NECK OF THE PICTURE TUBE IS FRAGILE SO ONLY GENTLE TAPS ARE TO BE USED.
If the blue jumps in and out, the tube is shorted.

The last check is to tap around the board with the three controls. It may be just a bad solder connection on the board that can be fixed with a low heat soldering iron and some good 60-40 electronic solder. If you find a sensitive spot on the board that causes the blue to come and go, that is good place to check for a bad connection. A component may have come loose over time.

Good luck. BE CAREFUL!

Smokey
 
  #3  
Old 04-22-01, 05:09 PM
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Thanks, Smokey! I appreciate the advice. I'll let you know what happens.

CEA
 
  #4  
Old 04-24-01, 04:01 PM
Smokey
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Thanks, cea. I love to hear how these things turn out. If we can cough a few extra miles into these old sets, it makes my day.

Smokey
 
 

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