CurtPalme.com Home Theater Forum

[incova]

I have been having some issues with getting my optical focusing correct and I was wondering whats going on. I have a a AMpro 4600HD with the dark green c element and red c element and G 90- Lenses. This is a stupid time to ask! but is this combination compatable?

I have the PJ as far back as I can, its now 127 inches from the front of the lenses to the screen. Using the Ampro calculations which are conservative I have read and checking the distance from the screen to where the ceiling mount pole would be if I had one instead of unistrut its 147.5 inches away from the screen. I should according to the manual have a screen width of 94.43 inches, in reality after doing all the geometry and leaving a 1cm gap between raster and tube edge I get about 99 inches width which is almost exactly what I wanted. I still however have a adjustement problem on all 3 lenses and I dont know why, I have moved the pj back 6 inches, the inside lens knob is still at the extreme of adjustment on all three tubes. I have redone the astig I think I am doing something wrong or my lens throw is not what I thought it is.

Any advice appreciated.

[stefuel]

You are using lenses that are not listed in the installation instructions so the lens throw calculations are not going to work so you are going to have to wing it.
Set the lens adjustment to the middle of it's travel. Project a cross hatch test pattern turn off the red and blue guns so only the green is on. Take a piece of white paper and hold it up against the screen. Now slowly move the paper closer to the green lens and see when it comes into focus. That's your sweet spot for throw distance.

[Curt Palme]

It is a bit strange, as the C element curvature hasn't changed with the Sony lenses. My guess is that the gap between the C element and the lenses is too far apart compared to the G90, Marquee and Barcos. THat's really the only difference with the Ampro. I'd carefully tighten the lens adjustment bolts up as tight as you can get them. You shouldn't be able to touch the C element with the back of the lens even if the springs are as tight as they go, although one Ampro 3600 owner managed to tighten the crap out of the springs and crack the front of his green tube with the back of the HD8 lens.... then wanted warranty...

[Curt Palme]

It is a bit strange, as the C element curvature hasn't changed with the Sony lenses. My guess is that the gap between the C element and the lenses is too far apart compared to the G90, Marquee and Barcos. THat's really the only difference with the Ampro. I'd carefully tighten the lens adjustment bolts up as tight as you can get them. You shouldn't be able to touch the C element with the back of the lens even if the springs are as tight as they go, although one Ampro 3600 owner managed to tighten the crap out of the springs and crack the front of his green tube with the back of the HD8 lens.... then wanted warranty...

[incova]

Thanks Chip, Curt, really useful stuff I will have a go at this on Monday and get back to it not at home at the moment, I didnt think of the gap between the lenses or using a card to find the sweet spot much appreciated.

[cmjohnson]

I am pretty certain that the "prescription" for the AmPro C elements was different than the prescription for every other version of the C element. I base this on my own observations when I took a green AmPro C element out of a scrapper LC assembly and put it into a Marquee LC assembly. It WOULD NOT FOCUS. I could have edge focus, or center focus, but not both at once. This was definitely an optical issue as the image on the CRT face was sharp all across the raster.

When I swapped back to a standard C element, the problem went away.


I also noted, by just looking at the two types of C elements, that they were visibly different. The flat flange section of the AmPro spec C element was wider, about 1/2 inch vs. about 5/16" for a regular C element.



These are just my own experiences, and I can't say with any certainty if the same holds true for ALL AmPro LC systems.
It's not impossible that AmPro used more than one type of C element, since they ran through several generations of
LC 9" projectors and some had Sony CRTs and some had Panasonic CRTs.



CJ

[incova]

Thanks, I remember that post but I had thought people agreed that this was not the case, I really hope it is not the case as that adds another layer of difficulty to this job. At present I have two coloured c elements, 1 dark green and 1 sony 1292 red, these combined with the g90 lenses should be ok compatability wise shouldnt they? I will start experimenting this weekend, see if I can get some answers.

[papalek]

I have your same combination on my 4600 and have no issues but I do have the lenses adjusted in about 3/4 turn more on the springs to put the lens closer to the C element.