CurtPalme.com Home Theater Forum

jbltecnicspro · Joined: 23 Apr 2016 Posts: 512

Alright, thanks to a generous member here, I am now the happy owner of two Sony G70's. One I'm going to use, and the other I'm most likely just going to keep around for parts (and tubes - which are in very good condition).

So I have to admit, I'm a little overwhelmed right now. I would like to get a screen, but I'm not sure which I want to get. I previously had my mind set on getting a 72-inch 4:3 screen, but the tubes in the functional G70 have 16:9 wear, so that's out of the question. I'm thinking of keeping the same width going - 57-inches, but reducing the total diagonal size to 65 inches so that I can basically have the 16:9 version of my original 4:3 size.

My wife is pretty handy with the sewing machine and fabric, so I was thinking about making my own screen for the projector. Problem is, I don't know what fabric to use, and what I should get. My basement, which is the primary viewing area, can be light-controlled. So I'm probably looking at a white 1.1 gain matte fabric.

Next up, I'm not sure if I want to ceiling mount the projector or not. I mean... I want to - so that we can sit close to the screen and enjoy its full glory, but the thought of aligning a projector hanging down just seems daunting to me. Any thoughts on this?

Since I have some other house projects that must be taken care of, I probably won't start this project until late into the summer. But any and all advice is welcome. Thanks! And I'm very excited to finally join the club of CRT projector owners. Smile

draganm · Joined: 08 Mar 2006 Posts: 8990 Location: Colorado

congrats

read this
http://www.curtpalme.com/CRTSetupGuide.shtm
then this
http://www.curtpalme.com/SonyG70_Layout1.shtm

then download , print, and follow the install manual
http://www.curtpalme.com/SonyG70_Downloads.shtm

If it has the older DVI card, you'll need the small DVI/HDMI form factor converter plug

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

I strongly recommend sticking with the 16:9 pattern because as long as you are not an old movie buff, the 16:9 pattern will fit
your movie watching habits better than 4:3 will. And for many reasons you DO want to try to use as much phosphor area as
you can, but without crossing outside of the wear pattern, which will be instantly annoying.

I myself am running a 2:1 aspect ratio screen which is nothing but a sheet of masonite painted with Behr ultra flat ultra white paint, applied via sprayer. This is a dirt cheap way to make a screen (add a few 2x2s for bracing, screw them through the masonite, use drywall putty to fill the screw heads and sunken spots around the screws) and it'll give you a great, cheap, low cost starting point
for the screen. After you use it for a while then you will have a better idea of what else you may want from a screen.

I have personally never bothered to switch to a different screen. This cheap DIY screen really does a very good job. It's big enough, cheap enough, and suits me just fine. I can't complain.

jbltecnicspro · Joined: 23 Apr 2016 Posts: 512

So now I have to admit that I'm a little confused about screens. I see the gain numbers tossed around 1.1, 1.3. I also see brightness values tossed around too. 12 foot/lamberts. How bright/dim are CRT projectors anyways? Do I have to completely pitch black my room? I would like to have a screen that's bright enough to not have to turn down the lights all the way to watch it, and I would like to not have to crank up the contrast to see it either.

I'm used to calibrating my monitors at around 85 cd/m2 for all white (no window - full screen). My monitor right now is hanging at around 90 cd/m2. I'm guessing that this kind of brightness isn't really possible with a CRT projector?

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

CRT projectors use generally not more than three 8.6 inch diagonal CRTs, (we call that size a nominal 9 inch) so you can
not expect amazing brightness out of them.

You WILL want to run the projector in a well darkened room. The darker, the better.

It's not that the projector can't deliver adequate light output, it CAN, if the screen is not too large, but it is a
matter of black level.

With ANY front projection system, the ambient light on the screen with the projector in standby determines the absolute
lowest black level that will be seen. Obviously if the room has a light on, the blackest black you can see will be a shade of
grey. In a well lit room, your black level will be bright grey/dim white.

Front projection requires a fully dark room for best results.

As for screen gain, the tradeoff of screen gain is that the higher the gain, the narrower the "good" viewing area in front of the screen will be.

In a well darkened room, you don't NEED a gain screen, but you might LIKE one. But a unity gain screen (1.0, basically equal to a flat white painted surface) will give you an unlimited viewing angle.

the dude · Joined: 11 Sep 2013 Posts: 179

One more tip:

Be carefull with contrast. The G70 is only a 8 inch set, but is very bright (for 8 inch). That means it eats tubes when setup bright because it can drive them very hard. You can create a visible wear pattern within a few days when cranking up the contrast. Really! NEVER EVER go higher than 80 for a longer time. The actual birghtness will depend on the sets gain settings of course, so thats a approximate value.

jbltecnicspro · Joined: 23 Apr 2016 Posts: 512

the dude · Joined: 11 Sep 2013 Posts: 179

This is a very small screen that will give you a bright picture for sure, thats 1,524 meters right? (i live in the metric part of the world). I would choose a bigger screen, at least 2 meters (6,56 ft). High gain will help for sure. But too high gain is also problematic, because it causes color shift. The color shifts to blue on one side and to right on the other because the amount of reflected lights depends on the angle, wich is slightly different for the individul tubes depending on the viewing position.

jbltecnicspro · Joined: 23 Apr 2016 Posts: 512

Alright, so I have the projector on the floor, aimed at the wall that our screen will be fixed on. I'm just running some internal test patterns (1600x1200 at 85hz I believe), and it's obvious that the image is using some unused phosphor area outside of the 16:9 wear pattern (it's a little brighter than the rest of the image). First off, even with the wear on the tubes this projector is a lot brighter than I was expecting! Whew! I'm projecting onto a light-brown colored wall, so I'm very hopeful that our projector screen will look great.

Second... I'm a little confused as to how I should setup the raster... The G70 manual, from what I can see, doesn't mention setting the raster. I'm guessing that I need to just use the RGB size and center controls? Is there such thing as a "raster" adjustment on the Sony G70? It appears that there may not be. I'll continue messing with it and reading the manual and see what I can derive from it.

**Curt Palme** · Posted: Mon May 30, 2016 2:21 pm Post subject:

Shrink the raster so that it fits within the wear area, then move the projector back to fill the screen back up. use the 'size' control to do that as well as the middle 'zone' command to shift the raster so that it's within the wear area.

the RGB size and shift functions are used to make sure the RGB image doesn't overshoot (or undershoot) the raster.

jbltecnicspro · Joined: 23 Apr 2016 Posts: 512

Thanks Curt! I did some more finagling and I found that turning on ABG (I think I got that right - it's the equivalent to the AKB of the 1292) and turning up the brightness helped me to see the raster more easily. One thing I noticed though is that both blue and green were displaying retrace lines on the face of the tubes when I did that. Red did not. I checked the timer, and it looks like the set has almost 8200 hours on it. Is this a weird ABG issue? Or are my tubes pretty old at this point and need replacing?

Also, when I tried to do some adjusting of the projector, I couldn't save to all memory blocks, which was kind of annoying. Even when I did it like the manual said (hold Memory down for five seconds and then confirm), the projector never prompted me to save all registrations. Instead, it just kept saving and re-saving. What could be going on here?

**Curt Palme** · Posted: Mon May 30, 2016 6:57 pm Post subject:

Old tubes >5000 hours can do strange things either with ABG on or off. Use the setting where you get the best b/w balance.

If it said 'save' in the menu, then it is indeed saving the settings. the manual may be a slightly different firmware than the set, but almost all Sonys will simply save the settings automatically when you press 'memory'.

teh tubes will have a reduced emission at 8200 hours, but they are discontinued now, although I think VDC may have tubes at $500-600 each. Not worth retubing at this point.

jbltecnicspro · Joined: 23 Apr 2016 Posts: 512

the dude · Joined: 11 Sep 2013 Posts: 179

jbltecnicspro · Joined: 23 Apr 2016 Posts: 512

the dude · Joined: 11 Sep 2013 Posts: 179

You can swap the neckboards and tubes without problems.

jbltecnicspro · Joined: 23 Apr 2016 Posts: 512

Okay, so I have been watching Graham Johnson's setup DVD and have been reading everything on CRT setup but I'm still a little confused of what's going on. So here are my questions.

Essentially, to setup a projector, I have to do the following:

0. Physically align the projector with the screen.
1. Center and maximize the size of the rasters on all three tubes, starting with green.
2. Make sure the rasters are all centered properly (as properly as can be with the wear pattern of used tubes). Perfectly centered rasters mean that all tubes' rasters are in the same positions and sizes as one another.
3. Mechanically center the red and blue tubes with green using the adjustment screws on the back of the projector
4. Shape the geometry and get it as perfect as possible with Green, then rinse and repeat with Red and Blue
5. Do zone convergence if necessary
6. Adjust white balance and grayscale
7. Enjoy the damn picture

So I'm a little stumped at the moment regarding the test patterns and raster adjustment of the CRT. Please bear with me, as I'm probably asking some dumb questions here. So there is no explicit "Raster Center" mode on the G70. Not like Curt's NEC on his guide. When I set up the alignment in service mode, am I to assume that the test pattern I'm viewing on the screen is the actual raster adjust mode? I suspect it is not, as when I view Graham's video, the test pattern doesn't go out all the way. But what looks like the raster, does (the "not so black" part of the picture - which is the raster).

Am I to ignore the test pattern? Or am I to make it so that the test pattern stretches all the way out to the edges of the tube face (or wear pattern, in this case)? I can take some pictures if it would help clear up what I mean. Are the internal test patterns useless? I have an external pattern generator that I can use if it's better.

the dude · Joined: 11 Sep 2013 Posts: 179

Aligning the tubes is easy.

First, set ALL Convergence settings to midpoint, especialy the raster shift sittings. Then invoke the RGB Centering menu (there is a button on the Remote), this will give you a cross pattern. Now loosen the screws on the red and blue tube, then try to convergence the cross horizontally. Thats all.

You may check the center line also at this point using a laser level or measure if it is the same hight on both sides. Maybe you want to turn the defelction coils a few degree to correct. Be aware of high voltages, the horizontal deflection can cause nasty HF burns.

Also note that the G70 has a scheimpflug correction (lens flapping), when the angle of the CRT changes this setting may need readjustment. If sharpness is uneven (lets say the left is softer than the right) and this is not seen on the CRT frontplate, then you need to play with scheimpflug.

**AnalogRocks** · Posted: Sat Jun 04, 2016 9:15 pm Post subject:

I'll add: When adjusting the deflection coils, keep one hand in your pocket.
NEVER lean on the chassis with the other hand. If you get a shock the voltage will travel across your heart, if your hand is in your pocket you just do a little dance. Ask me how I know that. Laughing

jbltecnicspro · Joined: 23 Apr 2016 Posts: 512

Thanks for the help guys. One more thing is that I was thinking about going ahead and moving the tubes from the non working projector into the working projector. I plan on leaving all of the electronics on the tubes as I swap them. Will I have to perform any special service adjustment on them? I read something about a four-hour process when installing new naked tubes. But I should just be able to plug and play, assuming I swap all hardware?