CPD1604S Vertical Collapse

[vol.2]

Originally Posted by Alex KL-1

Interesting. In my 29" TV, even having a AKB circuit feedback, I prefer the image with somewhat low g2 setting. Also with one of my low-end monitor.

At least in this particular monitor, when I change the bias controls or the brightness, it shifts the DC offset of the whole video signal up and down.

The G2 doesn't demonstrably effect the DC offset, it just makes everything brighter on the screen, including the black becoming grey.


In other TVs and monitors, it has been my experience that I get the clearest, brightest picture by turning the color bias controls and brightness control all the way down and cranking up the G2 to compensate. My understanding is that this pulls the video signal way up away from G1 and shrinks the spot size, resulting in a sharper image. But in this monitor, if I try to do this, I get blooming and smearing at a much lower total luminance than if I do it the other way around.

I think maybe the Automatic Contrast Limiter is having some effect in the circuit that prefers it to be set that way.

BTW: If the pin #1 of the CXA not bring the desired range, or maxed out, perhaps adjusting the divider at the pin #2? Well suggestively labelled (BRIGHT)... If you already not played with this yet

I haven't messed with the Bright pin yet, but it did seem simple enough to alter the divider there.

Honestly, I'm thinking my best gains might be to pull the G1 down to about -100V and see if I can shrink the spot size that way. That will also allow me to raise G2 and get more brightness without increasing the swing on the video amp

I'm working on a circuit I can use to convert the +180V B+ to -100V for the G1. It should be high enough impedance that the load won't be an issue I think.