CurtPalme.com Home Theater Forum

[jbltecnicspro]

All of those G90's! So are you going to stack a couple of them for your viewing area?

[cmjohnson]

If I can figure out a way to make it happen, probably!

More likely I want to do a blend. I'd like a 10 to 12 foot wide picture.

[jbltecnicspro]

Hell yeah - I would love to see a blend/stacked system in my lifetime.

[cmjohnson]

I'm SERIOUSLY considering hanging two of them in my HT. But I'd want to do a blend and get a 10 to 12 foot wide picture.

But that would require me to radically change the rest of the system. My equipment rack is in the back left corner next to the screen, and I'd have to move it out. I need to simplify anyway. Clean out the dead wood equipment that really doesn't do anything
for me in the system anymore.

Installing two G90s on the ceiling is rather a daunting prospect. I do have two mounting bracket systems, though, which certainly helps.

[cmjohnson]

I'm going to have to make a choice. Marquee Ultras or G90s? I seem to have plenty of each....

That's for my own HT room. WHich is a bit small but it's what I have to work with.

It's nice to have choices.

[greg9518lc]

After having the opportunity to see Overclockers stack before he passed away in would go with the Marquee setup. For sure a much better image.
But do agree nice to have options.

[jbltecnicspro]

Marquee because they're more reliable... right? At least that's what I get off reading other forums.

Edit - and you also have people like Mike Parker developing mods for them still. So you could continue to scratch that upgrade itch.

[gjaky]

[cmjohnson]

I don't have enough experience with G90s yet to be absolutely certain but the overall opinion I've picked up over the years is that the Marquee CAN have the BEST video chain and deliver the best overall image if you want to put the time and money into it to get it to that point. But for that focus issue which will always plague the Marquee, that being that while its focus system does qualify as functional it is not optimal, the underlying reason being that the stock magnetics were made for 40KV Thomson tubes, not for 34.9 KV Panasonic tubes which are different in several important parameters, some of which affect focus requirements.

From a mechanical construction point of view, the G90 is (mostly) a much better engineered projector than a Marquee. There's really no doubt about that. The G90 is intensively engineered. The Marquee represents the minimum mechanical engineering necessary to get the job done.

[greg9518lc]

[quote="cmjohnson"]I don't have enough experience with G90s yet to be absolutely certain but the overall opinion I've picked up over the years is that the Marquee CAN have the BEST video chain and deliver the best overall image if you want to put the time and money into it to get it to that point. But for that focus issue which will always plague the Marquee, that being that while its focus system does qualify as functional it is not optimal, the underlying reason being that the stock magnetics were made for 40KV Thomson tubes, not for 34.9 KV Panasonic tubes which are different in several important parameters, some of which affect focus requirements.

From a mechanical construction point of view, the G90 is (mostly) a much better engineered projector than a Marquee. There's really no doubt about that. The G90 is intensively engineered. The Marquee represents the minimum mechanical engineering necessary to get the job done.[/quote]

After seeing what properly implemented mods and setup by the Guru the yokes and magnetics are not a problem with the Marquee. Also no way a G90 with all faults can you ever bypass the reality creation crap in them. The Marquee is as close to a straight gain device as you could ever have.

[cmjohnson]

DRC doesn't even operate if your input signal is higher than plain old NTSC. It's OFF when you're running HD. It's not an issue.

DRC is basically a line doubler which works in both the X and Y axes. It's a nice trick for watching analog NTSC TV but if you're
feeding HD into the projector it's not an issue. When it's turned off it's not affecting the picture at all.

The focus yokes in a Marquee ARE problematic. They NEVER deliver the performance that ANY other Panasonic tubed equipped CRT front projection system delivers because of the fundamental mismatch in the magnetic focus characteristics of a Thomson tube
vs. those of a Panasonic tube, and the Marquee uses Thomson magnetics made for Thomson tube. Electrohome chose not to do
what every other Panasonic tube user did, which is to follow Panasonic's recommendation and use Kanto-Denshi yokes which were
always specifically engineered for Panasonic tubes and for the projector that they went into.

I have found through experience that the stock Marquee yokes behave very badly if your LVPS is weak or unstable, having a reasonably fresh LVPS in your unit helps a LOT. But even then, run them at high contrast levels and they still lose beam control
at levels where a 909 or G90's focus system is maintaining sharpness.

I have confirmed this by actually running G90 focus magnetics in a Marquee test chassis. Due to several issues that have to be
overcome that's not a "ready for prime time" modification but I've been able to run one full G90 magnetics stack side by side
with a standard Thomson stack in the same machine. (Deflection, convergence, and focus) The G90 stack of magnetics clearly outperformed the Thomson focus yoke. But this configuration requires moddiing the HDM to get the image width into the right range, and it will soon overheat the HDM and eventually blow the deflection outputs. So until I work out the required interstage transformer between the G90 deflection yoke and the HDM, this isn't a viable retrofit.

Simply running the G90 focus yoke in a Marquee with the Thomson deflection yoke is functional, but it's far from optimal. You
can't even mechanically place the focus yoke where it needs to be on the tube. It needs to be used in conjunction with the
deflection yoke or it's never going to perform. And making the deflection yoke work correctly is where the holdup has been.

[cmjohnson]

For the first time in a long time I've actually been able to watch movies on my own personal Ultra in my own theater. It's been a long time, because I have been busy working on OTHER projectors so much and plus I have to do other things to make money to support this habit.

I'm still dialling this beast in and there's a way to go before it's running at peak performance but it's an Ultra with brand new LUG tubes, the best and freshest of that big lot I got a while back, running behind VDC edition HD-10L glass, which looks to me like
it's the sharpest kind of lens I've yet seen.

It has older (2006, I think) MP modded VIM and neck cards, and for now that's about it for mods. It does have an HDMI input card.


Nothing's calibrated, nothing's fully adjusted, and it's already delivering a beautiful sharp picture.

I'm going to put my best G90 on a cart and wheel it in and set it up right under the Ultra and be able to do an A/B shootout
some time very soon. First I've got to tweak the Marquee to peak performance.

I should even be able to stack the two and that should be fun.

THEN I can decide for myself which PJ is worthy of the ceiling mount. I don't think there's a bad choice, fortunately.


I've come up with a new way to set up Marquee magnetics which I think makes it easier.

Put the deflection/convergence and focus yokes on the tube neck. Don't put the CPC rings on yet.
Connect ONLY the convergence yoke cables to the HDM and VDM. For now don't connect the focus or astig yokes.

Of course, attach and connect the anode lead and neck card.

Power up the machine and now you can do basic mechanical alignment (yoke tilt and mechanical focus centering) with nothing
else interfering with them.

Now connect the convergence yoke and check that convergence movements don't have any off-axis components in them. Move to the top center of the raster and move the (green) convergence zone straight up or down. If the vertical lines bend to the side at all, you need to rotate the convergence yoke relative to the focus yoke. When it's correctly aligned and there is no horizontal movement of the line when you adjust vertical convergence, secure the convergence yoke in place on the back of the defleciton yoke with hot melt glue. This was done at the factory years ago but the glue often fails after some years on the projector.

With the deflection and convergence yokes delivering a true horizontal line and they're working together on the same axis,
now is the time to connect the focus yoke plug and do your basic focus.

Now do electronic astig. (Don't forget to plug the cable in!)

Now power down the unit, remove the neck card, and install your CPC ring set after first setting its rings all to the neutral zero position. (Tabs together and all the way around the back of the assembly relative to the adjustment knobs.)
Reinstall the neck card, power it up, and set the CPC centering/flare, astig, and 6-pole if you have it.

I am assuming you already know how to adjust all the individual magnetics. This process I outline just makes it easier
to get optimal results as you're not having to fight competing magnetic signals.


Since I've started setting up my magnetics following this procedure, I'm getting a sharper image to start with, and I don't even expect to have to touch the magnetics again. They should be RIGHT by doing it this way.

[jbltecnicspro]

Since you have both the G90 and G70 - how do they compare in terms of build quality, and mechanical engineering?

Edit: Also, glad that you're able to relax and enjoy your setup. Wonder how much Curt gets to enjoy his stack?

[cmjohnson]

I've only tested the G70 to ensure that it works. I can't speak as to comparative image quality as I have not made that comparison.

It's available but I'm not really supposed to offer a working projector for sale.
But if any body is interested, let me know. I'll give Curt a cut if I sell it.

Its tube condition is really excellent. I would not suggest replacing even the green tube, because it has so little wear on it that
you might not even notice it.

Build quality is very good. Mechanically it's laid out more like a Marquee but the construction of it is classic Sony. Well engineered.

[jbltecnicspro]

[cmjohnson]

Stunning improvements have been made in my garage/workshop. With continued improvements I will be able to set up the garage, temporarily, as a home theater featuring two side by side 8 foot wide screens.

This will allow me to do side by side matching and evaluation of projectors to be sure that when they are ready to send to their
next homes they will be rather well matched and calibrated. If I had any blending equipment I'd play with that idea, too.

I need to think about that. Assuming running both PJs in 4x3 mode and I want to blend them to a 16x9 screen profile, how much overlap is that per PJ?

Answer: 128 inches screen width for a screen height of 72 inches. Two 8 foot wide screens are 192 inches so the blend zone
width is 64 inches or 32 inches per projector. That makes a good sized blend area and maximizes CRT phosphor area in use.

[thewolfman]

Ok, now that you have 2 pj:s next to one another, why not take some pictures? I for one are interested in close ups of the grid pattern with your different units and your inventions. Like, is it really necessary with moving around the focus coil - for the sweet spot - over having them all the way forward. I have only repositioned the coils once before but felt right away that all the way forward was the way for me, but only spent a minute or so doing it. Your other tips and trix of setting things up I have never done either, but rest assure they are locked away for a rainy day too.

[cmjohnson]

Can't do it yet. Have not YET even bought the screen materials and there's still much to be cleaned up and disposed of in said garage before I can do it.

[thewolfman]

Ah, yes. Fast read and got excited.

[jbltecnicspro]

So to make sure I have this right. Stacking is overlaying one projectors image onto another. Blending is having one projector cover one half of the screen and another covering the other half?