CurtPalme.com Home Theater Forum

[Cube]

I got my 1272 set up at 1080i. (Tested both an HDFury 1 and a Moome DVI card (first generation), and honestly the picture looks identical between the two.) Now I've been testing the picture on various stuff and I'm having a problem with static contrast (bright and dark areas on the same screen).

First off, I find that setting the RGB Enhanced option on my Blu-ray player gives a much better black level but it kills some of the shadow detail and adds obvious stairstepping in a smooth gray gradient. Putting it to RGB Standard gives a better range of detail but the black level is poor, and no matter how I adjust the stuff on the remote (Contrast, Brightness, Bias, Gain) I can't get a good black level without making the whole picture too dark.

Putting black level aside and just looking at the static contrast, colorful mid-range stuff like Pixar, or vary dark scenes like the opening scene from Revenge of the Sith, look terrific. However, high-contrast scenes like the daytime Chicago scene at the beginning of The Dark Knight look absolutely terrible. There's no detail in the shadows and the bright parts are blown out.

I'm not sure what to adjust next to fix the problem. It seems like using the HDFury plus an external RGB gamma booster might help with the shadow detail but I don't want to crush the whites any more than they are. If it doesn't help I'll just be out about a hundred bucks I guess.

I've been seeing old threads about disabling AKB with a jumper somewhere and adjusting the G2 knobs that the manual warns you not to touch. I'm not sure where to begin there... I can't figure out how to lift up the top electronics board to get at the G2 voltage testing points or if you're supposed to adjust them with the projector unplugged or not. I also don't know which pins to short to disable AKB or whether to leave it off after I'm done. On my Mitsubishi CRT monitor I had to go into the factory menu and mess with G2 and Bias manually to get proper contrast and color balance, so I'm not afraid to do it again here, but I don't want to permanently damage anything or burn out the tubes (or electrocute myself).

Could anybody post a photo of where to short the AKB and how to hinge up the top board?

[rosenbush]

Once you remove the cover, you'll see the first set of boards, (Check the pic at http://www.curtpalme.com/Sony125x_Layout1.shtm ) you'll need to remove 8 screws, 4 at the bottom at the picture and 2 by each side. Pull up and you wll see a small board at the lower end in the first picture herehttp://www.curtpalme.com/Sony125x_Layout6.shtm just right next to the connector on that board there is the AKB 2 pines. You can use a jumper as the pc hard drives has to bridge them.
About you're blacks problem, what are you using as screen?

[Cube]

Thanks. I figured out how to lift the board last night. (I think I had to remove 12 screws though.) Once I got at the voltage testpoints I experimented with it for a long time and now I think I have a better idea of what's going on. Correct me if I'm wrong about any of this.

There's a pair of pins you can short to disable the AKB function, which seems to act like a dynamic contrast adjustment that overrides whatever you do with the G2 knobs. As long as AKB is turned off I can force a nice black level but then various other functions don't work correctly (Brightness, Bias, RGB cutoff). I saw one poster on AVS who suggested running with AKB off all the time but after comparing the black levels, the projector seems to work best with AKB left on and lowering the brightness. So now I'm doing as the service manual suggests and only disabling AKB long enough to adjust the G2 knobs visually.

I read in another thread that the first-generation 1272 should have the G2 voltage at 4.0v and the 2nd-gen should be 1.5v. My set seems to be a 1st-gen but I know it was retubed before I got it so I wasn't sure which setting to use. I started by setting the G2 to 1.5 but when I checked the tube face with AKB turned off, it was way, way too dark, so I'm guessing 4.0v is the right figure. Anyway, I decided on a compromise of 2.75v which is about what I arrived at using the visual G2 adjustment method.

After I got that far the color balance was already pretty good and even with AKB turned back on I could get a decent black level by lowering Brightness (~40%). I'm using a white matte screen in a totally dark room so it shouldn't be an issue. The only problem is the dark details get lost a bit. I think this is the usual CRT gamma issue so I'm going to go ahead and get a Gamma-X and see if it helps. Except for that aspect I'm feeling pretty good about the image quality now.

There's something else I've noticed and I'm not sure if it's a defect with the projector or a common thing. There's a bright line at the very top of the raster (above the AKB line) that never goes away, even with top blanking. I'm guessing it's some artifact from the gun finishing the raster scan and heading back to the start. Does this sound normal?

[rosenbush]

If you use light gray screen , will help you on your blacks. It worked for me. If you use white, it will "wash" your colors.

[ecrabb]

[rosenbush]

Yes, I read about that too. That's why I keept the white screen for I while, But I wasn't happy with the contrast, until I try a small part with screen paint (silver white), and I really liked the difference, then I painted the whole screen. Since then I'm happy with it. As I said, worked for me.

[ecrabb]

OK, so silver-white/gray... That's a little different than "light gray"... If it's silvery, then you may be getting some additional gain. What was the white surface before you painted it?

SC

[rosenbush]

It was flat white. You're right "light gray" 'per se' won't help, I was trying to make it simple, but also can be confuse.