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Nashou66
Joined: 12 Jan 2007
Posts: 16171
Location: West Seneca NY
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| Posted: Thu Feb 28, 2008 2:10 am Post subject: Red out of focus |
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I was changing the op amp on A Marquee vim the first one on the red channel . Put it in tested it. all fine. then i did all the other colors only the first ones in the chain. went to test and the red is out of focus. when i lower the contrast it gets in focus. the other channels seem to be fine. No blooming. I looked at the schematics and the contrast goes through the AD834 chip. think that could be the cuplprit? My other VIM is fine so its not anyhting else in the projector. I tried another op amp back on the red and its the same thing out of focus.
I should mention that its only when its an external source, the internal red grid is as sharp as the rest.
Athanasios
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tse
Joined: 03 May 2006
Posts: 1014
Location: Sweatbucket, Fl.
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| Posted: Thu Feb 28, 2008 3:41 am Post subject: |
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All video goes through the multiplier chip (AD834) so you would think if it was bad all your signals would be bad. The out of focus condition might be because there is oscillation in the video signal? If it is definately the VIM causing it, that would be my guess. Here's where you need to break out the scope...
Scott
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Nashou66
Joined: 12 Jan 2007
Posts: 16171
Location: West Seneca NY
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| Posted: Thu Feb 28, 2008 7:24 am Post subject: |
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Thanks Scott, The weird thing is I thought it might be the oscillation but the other channels are fine with the same op Amp. I might have to switch an ad834 from a different channel. Looked up the price for them 27 bucks !!!!!!I wonder if it could also be the output op amp , last one in the chain? that is the same original one.
Athanasios
_________________
Don't blame your underwear for your crooked ass~ unknown Greek philosopher
"Republicans believe every day is the Fourth of July, but the Democrats believe every day is April 15." --- President Reagan
One Smart Dog!!!
Marquee High Performance Bellows now shipping!!
Marquee Modifications and Performance Enhancement
Marquee C-element and Bellow removal
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