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Discussion Starter · #1 ·
So I sold a brand new (we all think) ECP 4500 recently after having run it for 24 hours. This set did not have mark on it, tubes, screws, case, etc, so for all I know it was NOS gov't stock.


The first minor problem that developed after it was shiped to Quebec was the convergence board had a bad connection on it, causing lines in the raster. No biggie, we found that one right away.


Now, after a tech that knows E'homes quite well it seems set the unit up, there is a distinct change in brightness exactly 1/2 way across the screen. 1/2 of the screen is glowing green, the other is black, and when a signal is applied you see a change in brightness.


The tech that adjusted and installed this set apparently installed several of these back in 1996/1997, and seemed to know his stuff. He only speaks French, so I did not talk to him directly, but got translations through the customer that bought this.


I've never seen a symptom where 1/2 of the pix (I can't remember if it's the right or left hand side) is significantly brighter than the other 1/2. The internal test grid does not seem to show this issue.


Any ideas?


Curt
 

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That sounds an awful lot like what happens when you push the raster to far to one side with the move button. I can make the picture go to a weird high contrast black streaky image... other than this, I've never seen anything like you describe...
 

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Discussion Starter · #3 ·
Yes, that's what I thought, but the customer confirms that the raster is centered.


Curt
 

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Is it the actual image that's brighter on one half? This problem goes away with the internal crosshatch displayed?


Cary
 

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Discussion Starter · #5 ·
Yes, Cary, that's apparently it. Even with no source connected, one 1/2 of the raster glows, the other 1/2 is black. Apparently before the tech aligned the set, the red was doing it too, but now it's only the green. I'm wondering if the tech misadjusted something, this sounds more like an adjustment issue than a part failure..


Curt
 

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I've got four 4500's right now and they all do that (on all tubes) with no source applied. I believe it's the clamping circuit on the neck boards that increases the brightness during the "clamp time". Wierd that it's only green. When I apply a source to these 4500's, they're ok. The only thing I can think of without spending time with a scope on it is to adjust R8 for maximum brightness (B at 10, C at 0) and then adjust R5 for 140V cathode voltage (B at 5, C at 0).


I'm a few days away from messing with these 4500's again (want to set them up for sale) but I'll keep this in mind in case I stumble across a solution.


Cary
 

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I had a simular problem, probably not as bad as you describe. I fixed it by doing the Color balance and video alignment procs in the service manual.
 
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