CurtPalme.com Home Theater Forum

Gerbrand · Joined: 13 May 2008 Posts: 199

All,

I recently bought a set of new P19LUGs from Terry and today I finally found time to start installing them in my 1996 BG1209s. This model does not have adjustable Scheimpflug. Instead it is fixed for a screen width of about 2.40 m.

When I removed the tube cover, I found a sticker on my original tubes saying "Special Scheimpflug corrected CRTs". So I suppose this means that something special has been done to these tubes to enable the Scheimpflug correction.

Now I have the following question: if I mount my new LUGs in this set, will I loose the Scheimpflug correction?

I have included a picture of the red tube + LC chamber below.

Thanks for your help,

Gerbrand

zGman · Joined: 22 May 2006 Posts: 599

Before you remove the tubes from the housings - measure with c-element removed
the distance from the front of the housing to each tube corner. this offset will be the
flapping adjustment which will be optimized for a particular throw distance, possibly
listed on the PJ somewhere. Possibly you could make a jig using the old tube/housing
so that you can glue the new ones in at the same orientation.
G

Mark_A_W · Posted: Tue May 25, 2010 2:20 am Post subject:

It's just added spacers isn't it?

zGman · Joined: 22 May 2006 Posts: 599

I don't know Mark - I have a similar housing here and there is no internal support for the tube -
just dug it out and had a look again today - really odd. I know some one in europe ( Ile? ) did
a 8" tube in 9" similar housing conversion and used the Barco program to calculate the flapping
corrections and made spacers (i think - it was a while back)

My concern for this setup is that he won't know if there are internal spacers until it's too late....
Seems best to take measurements and/or make a jig before cutting out the tubes.
And of course they will all be different.

G

Gerbrand · Joined: 13 May 2008 Posts: 199

Thanks for your help so far. Hopefully Ile (?) chimes in, if he was the one who did this.

I am also concerned about the required accuracy here. I did some rough calculations at it seems as the required accuracy is of the order of 0.05 - 0.1 mm (1 or 2 mil for the Americans). This is not something you can do easily with a simple jig, but requires a machine shop.

I may be wrong, so I will spend some more time looking into this.

Gerbrand

Ile · Posted: Tue May 25, 2010 7:31 am Post subject:

Gerbrand · Joined: 13 May 2008 Posts: 199

That is encouraging! I will have a look at your thread.

On the sticker on the tube it mentions alpha=10.5 degrees, which of course is the vertical Scheimpflug. It also mentions TCL=408 cm. Any idea what the TCL stands for?

Cheers,

Gerbrand

Ile · Posted: Tue May 25, 2010 11:15 am Post subject:

Gerbrand · Joined: 13 May 2008 Posts: 199

This is the the output of LENS for my set-up. As you can see the Scheimpflug for my tubes is actually not quite correct for the screen width I use.

After reading your thread about "poor man's lens flapping" I had one question: what reference do you use for the plastic distance holders. One side it is the tube face, but on the other side ? Is it something that holds the C-element or the C-element itself?

Thanks,

Gerbrand

zGman · Joined: 22 May 2006 Posts: 599

The housing I have here is just a cast aluminum chamber with no provision
for spacers....I am not going to post pics, but Ile may have some. I have no idea how
Barco put the things together but there must have been a production jig to set the
spacing from c-element to tube face. Whatever you do, I would recomend getting some precision
calipers and measuring the distance to the tube face before cutting out the old tubes,
so that you have some reference. If you were local I would volunteer to help with
measuring and machinework just for fun...maybe you can find a knowledgeable
local enthusiast and /or machinist? Best of luck with the project.
G

Mark_A_W · Posted: Wed May 26, 2010 4:40 am Post subject:

zGman · Joined: 22 May 2006 Posts: 599

Hi Mark - From what I have here, the tube is just glued on the sides to the housing - no spacers
of any sort - "willy-nilly" you might say. Hence my conclusion there must be a production jig.

Later model 1209S housings use plastic buttons to set the spacing, but that is not the case for
these early models - in engineering speak the early models are a "Kluge" - similar in concept
to the oil spill technology ruining our gulf coast - skip some steps and hope for the best...

just not so funny anymore.....sigh....!

G

Mark_A_W · Posted: Wed May 26, 2010 5:37 am Post subject:

LOL I think you mean "kludge" Galen Wink

But I understand what you mean.

Ile · Posted: Wed May 26, 2010 12:09 pm Post subject:

Ile · Posted: Wed May 26, 2010 12:27 pm Post subject:

Here's shims for 235cm projection distance and projector not tilted. Used straight mm values from lens program.

Added 0,5mm to all corners, so now also zero corners have 0,5mm blade gap. It's easier to cut tubes out when needed to replace.

Gerbrand · Joined: 13 May 2008 Posts: 199

Thanks Ile for all the helpful tips and images. It really seems "doable" to me now. One more question, though: how did you manage to cut the plastic shims to the required precision?

And why not use metal shims? I know you can buy metal strips with well defined thicknesses (e.g. 0.1 mm). You could use a stack of those.

Gerbrand

Ile · Posted: Thu May 27, 2010 7:03 am Post subject:

Gerbrand · Joined: 13 May 2008 Posts: 199

Hello,

Yesterday I had a chance to take the blue tube out of the projector. When I posted a photograph of it (below) on the Dutch htforum, it was pointed out to me that I actually have LC chambers of a newer type than Ile. Mine are made out of cast aluminium and apparently do not have a flat surface at the back, that can be used to glue the tubes against.

Basically it looks like that trick with plastic spacers might not work.

The only reference plane I can really trust, it seems, is the surface that the C-elements are bolted onto. So I think I should go for the following option:

First make an Al plate that can be bolted onto the chamber instead of the C-element. In this plate make four threaded holes, that can be used for reference bolts. Basically I screw those bolts in until they hit the surface of the tube. I can then use the bolts as a reference for glueing.

Does this sound like a good idea to you or are there better options?

Regards,

Gerbrand

Ile · Posted: Tue Jun 08, 2010 9:02 am Post subject:

I guess there is machined plane against tube face plate, that is now under rtv.

Gerbrand · Joined: 13 May 2008 Posts: 199

I would really like to be sure about that before I cut the tube out of its housing. Does anybody happen to have pictures of exactly this kind of housing without the tube? Or would I be able to see this when I take off the C-element?

Gerbrand