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Crumbtrail TV Forums: TV Equipment: TV Repair Forum:
No Picture

 
 


Wiz
User


Sep 16, 2005, 3:37 PM

Post #1 of 9 (1779 views)
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No Picture Can't Post
Hey, I have a phillips 28" widescreen, that was shorting heater to blue cathode. I was luckily able to stop it shorting by giving it a 'tap' while the heater was on. New problem though. The blue screen has now gone, however, no picture is there. There is voltage on the anode, as temporarilly shorting heater to cathode makes bright blue again. After doing this, a picture came up, but with only the red colours and blank for where everything else should be. There was no sound. However this quickly went, and now there is a blank screen again. Could the problem be the shadow mask (it makes an echo sound when tapping the tube), or could there be any other problem(s).

Oliver



mel
Veteran

Sep 16, 2005, 9:55 PM

Post #2 of 9 (1767 views)
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Re: [TheOW] No Picture [In reply to] Can't Post
A slipped shadow mask will only cause color putity problems (usually a "rainbow" affect). Check the screen and cathode voltages. Screen should be around 300 and cathodes should be around 150.


Wiz
User


Sep 18, 2005, 2:10 PM

Post #3 of 9 (1756 views)
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Re: [mel] No Picture [In reply to] Can't Post
Fixed.
The screen Voltage was at 64, so i turned the control back and forth a few times, and now it at 294, with a great picture.


Wiz
User


Sep 19, 2005, 8:01 PM

Post #4 of 9 (1737 views)
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Re: [TheOW] No Picture [In reply to] Can't Post
Why does the screen show a small (7cm) rectangle of different colours, after the TV is unplugged, This rectangle gets smaller and is gone after 15 seconds?????


mel
Veteran

Sep 19, 2005, 10:02 PM

Post #5 of 9 (1732 views)
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Re: [TheOW] No Picture [In reply to] Can't Post
The cathodes are still emitting and you have residual high voltage after you have lost vertical and horizontal sweep. As the heaters cool, the cathodes stop emitting. Depending upon the intensity of the residual beam, it could eventually cause a burn spot in the phosphor.


Wiz
User


Sep 19, 2005, 11:03 PM

Post #6 of 9 (1729 views)
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Re: [mel] No Picture [In reply to] Can't Post
So is this not normal. right? Is there anyway of stopping this happening? / How do I stop the resisual high voltage?

Thanks


Wiz
User


Oct 6, 2005, 10:54 PM

Post #7 of 9 (1663 views)
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Re: [Wiz] No Picture [In reply to] Can't Post
I am thinking of selling this TV to a friend, for a nominal fee because of this rainbow like effect when turned off. Is their anyway of fixing this problem/what could be causing the residual high voltage?


mel
Veteran

Oct 7, 2005, 9:48 PM

Post #8 of 9 (1647 views)
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Re: [Wiz] No Picture [In reply to] Can't Post
You will always have residual high voltage. I suspect that the problem is more associated with the original internal short in the CRT. I don't have a schematic for that model so I can't be more specific.


rrobor
Veteran

Oct 7, 2005, 10:56 PM

Post #9 of 9 (1646 views)
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Re: [mel] No Picture [In reply to] Can't Post
Agree with Mel, you have a fault in your tube still, and its not repairable, if turning up the screen voltage cleared something and tapping cured another something is on the move in there. One thing you could try is laying the TV on its face and then tap the tube, the odd time this lets the rubbish fall clear of the guns. Dont sell this to a friend, its not worth losing mates for a couple of dollars.

 
 
 


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