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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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Sharp 28JW-73H - Intermittent Flicker
Hi,
I'm trying to research a fault a friend's TV has. A picture paints a thousand words, so two shots follow this brief description. Sharp 28JW-73H / 29JW73H (GA200 Chassis) After the TV has been turned on for a few minutes a strong green and yellow flicker appears on all inputs. I will have the opportunity to preform a visual fault finding investigation in the next couple of days, but in the meantime does this fault ring any bells with the engineers in this forum? The photo shows a bar, but in real-time, the bar is not visible, just a stomach churning flicker at high freq. There is no vertical rolling visible either. I will be able to open up the TV in the next couple of days and check for obvious faults, and am capable of replacing them, however if anyone recognises the type of fault straight away I would be glad to glean some of your wisdom. best, Alasdair Photos: http://www.alasdaircampbell.com/flicker.jpg http://www.alasdaircampbell.com/flicker2.jpg |
#2
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Sharp 28JW-73H - Intermittent Flicker
Alasdair Campbell wrote:
Hi, I'm trying to research a fault a friend's TV has. A picture paints a thousand words, so two shots follow this brief description. Sharp 28JW-73H / 29JW73H (GA200 Chassis) After the TV has been turned on for a few minutes a strong green and yellow flicker appears on all inputs. I will have the opportunity to preform a visual fault finding investigation in the next couple of days, but in the meantime does this fault ring any bells with the engineers in this forum? The photo shows a bar, but in real-time, the bar is not visible, just a stomach churning flicker at high freq. There is no vertical rolling visible either. best, Alasdair Photos: http://www.alasdaircampbell.com/flicker.jpg http://www.alasdaircampbell.com/flicker2.jpg I assume we are talking about CRT Display ! A problem with the Degaussing Circuit ?? affecting the Electron Beam,only. Not the Power Supply and the Sync , and Video circuits After a few seconds the Degaussing circuits should shut down. In this case , it does not ! and would apparently affect all inputs. It looks like my CRT Monitor, a few seconds into Warm-up when the Degaussing Circuit is still Active ! The Flicker is due to the fact that your scan rate isn't the same or close to the Power Line Frequency ??? Yukio YANO |
#3
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Sharp 28JW-73H - Intermittent Flicker
On Sat, 16 Feb 2008 01:58:02 +0000, Yukio YANO wrote:
I assume we are talking about CRT Display ! Yes, sorry for not making that clearer. A problem with the Degaussing Circuit ?? affecting the Electron Beam,only. Not the Power Supply and the Sync , and Video circuits After a few seconds the Degaussing circuits should shut down. In this case , it does not ! and would apparently affect all inputs. It could be degaussing related, as when power is applied from cold, the problem takes a few minutes to appear. After successive power cycles, the problem is immediate. Perhaps that's a red herring though. It looks like my CRT Monitor, a few seconds into Warm-up when the Degaussing Circuit is still Active ! The Flicker is due to the fact that your scan rate isn't the same or close to the Power Line Frequency ??? Yukio YANO Which board in a modern CRT controls the scan rate? Alasdair |
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