CurtPalme.com Home Theater Forum

zGman · Joined: 22 May 2006 Posts: 599

Hi,

Lots of nice work guys! here's something you may find interesting as well.....

The BG808S with KF-3205 and 1208S/2 with KF-3203 both use a "reversed"
coil on green (KF-3205G and KF-3203G). This is easily verified by repulsion/attraction.

I installed an extra "G" coil onto the red tube just for experiment's sake a year ago,
there was no improvement in focus, but the geometry&convergence for the Green and Blue
were seriously affected by the reversed "G" coil placed on Red.

My conclusion was that Barco had reversed the green magnetic field in order to balance
the overall field in the chassis, possibly helping with geometry/convergence/linearity issues.

Cheers,
Galen

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

I was wondering about that possibility but wasn't ready to risk pulling the beam right off the phosphor face and burning a hole in the neck of the tube. If Barco was willing to take that chance, then I'm glad for it.

Reversing the middle coil's magnetic polarity seems like it would be good for balancing the overall magnetic field.

This might result in simpler alignment, too, as I have noticed a SLIGHT bit of interactivity...I think. Move the red focus coil
and the green image moves just a little bit. Or so that's what I THOUGHT I saw.

CJ

garyfritz · Joined: 08 Apr 2006 Posts: 12088 Location: Fort Collins, CO

Joust · Posted: Wed Sep 05, 2007 5:35 pm Post subject:

garyfritz · Joined: 08 Apr 2006 Posts: 12088 Location: Fort Collins, CO

No you don't have to move them to a Thompson shell, but yes you DO have to change the wiring?

When you say you "turn" them -- do you mean you flip the unopened shell front-to-back, or you open the shell and flip the coil inside front-to-back, or you rotate the shell on the tube, or...?

I just looked at my KF22-11's. I don't see any mechanism to move the coil on the tube neck for raster centering. I haven't tried slipping it onto a tube but it looks like it just fits snugly and has no centering movement. Am I missing something?

Joust · Posted: Wed Sep 05, 2007 6:16 pm Post subject:

you can flip the entire thing but you can get it much closer to the front by rotating it inside the shell.
Yes you do have to make a new harness. I simply replaced the ends on the stock Sony harness I'll take some pictures of Gino's new harness tonight.

You are correct, there is no centering mechanism as found on the thompson but it is not needed. the DK yokes are made much better and do not require it. my old thompsons could not move enough to center the beam on my red tube. I put on the DK yoke and the beam was smack dab in the middle.

BTW, I just got a reply from Sony Canada. the Good news is the yokes are available new from them. the bad news is that they are $415 each. so for a mere $1245.00 plus 14% tax, you can have a set.

antorsae · Joined: 16 Jul 2006 Posts: 297

IMPORTANT UPDATE: You DO NEED to reverse the polarity inside the shell. Once I installed the 3 focus coils in their original polarity the image on all 3 rasters was rotated around 30 degrees. I took the precaution of turning contrast down to 10 before turning on the PJ, so it did not make any damage.

Maybe the magnetic field is different and it affects the deflection coils, I don't know, but I took everything apart again, reversed the polarities (to match the original stock Thompson polarity) and voila... rasters are horizontal again.

In addition, I have also found that once installed; I needed to rotated the focus coil 180 degrees around the neck to get the raster centered on the tube face (that is, the cables would come out from the bottom of the tube). That got me some mechanical rastering centering so hopefully I can avoid static convergence (specially concerning on green).

BR - Andres

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

Frankenyokes do require about a 30 degree raster rotation via the deflection yokes. This is normal. Nothing to worry about.

What's important is that the beam stays on the phosphor face or at least doesn't get past the silvering. That's a troublesome
condition if it happens.

CJ

Joust · Posted: Thu Sep 06, 2007 2:16 pm Post subject:

I did NOT have to turn my raster.
CJ,
perhaps you were running into the problem that Antorsae described as a result of not turning the yokes inside the shell?
IIRC Chris Nuttal did have to rotate his deflection coil a bit but no where near 30deg. He said 10 or so. Mine were about 2-5 deg and i adjusted it out without issue.

antorsae · Joined: 16 Jul 2006 Posts: 297

Same over here, with the reversed polarity (vs. the stock 22-22/G90 yokes) there is no need to tilt the deflection yokes.

I was able to do mechanical raster centering by turning the focus coil around the tube neck. Just finished with one projector. I have NEVER seen my projector this sharp. I am running contrast 80. Amazing.

garyfritz · Joined: 08 Apr 2006 Posts: 12088 Location: Fort Collins, CO

OK. So with my KF22-11's, I should be able to:

* Use the current shells, and not transfer into Thompson shells.
* Open them up and reverse the coil.
* Wire up a connector as described in the FYoke I writeups.
* Slip them onto the necks (as far forward as possible?) and hope they center the rasters properly.
* If they don't, I can move the coils into Thompson shells to regain centering adjustments.
* Level rasters if necessary.
* Adjust my CPC tabs to shape blobs in the center as round as possible, because I won't have any electronic astig adjustment; with luck I won't miss it.

Am I missing anything?
Gary

Joust · Posted: Thu Sep 06, 2007 7:20 pm Post subject:

garyfritz · Joined: 08 Apr 2006 Posts: 12088 Location: Fort Collins, CO

Ah -- OK, thanks for that clarification. So either they work without centering, or they don't work very well at all. (Because you'd have to use too much electronic centering and your stability would probably suffer.)

This project gets simpler all the time! Smile

I guess the only thing I need to worry about is to make sure I wire it up right.

Joust · Posted: Thu Sep 06, 2007 7:31 pm Post subject:

antorsae · Joined: 16 Jul 2006 Posts: 297

Try to rotate the focus coil around the neck to see if you can move the raster. It has worked for me. I've been able to center the raster that way.

Best - Andres.

garyfritz · Joined: 08 Apr 2006 Posts: 12088 Location: Fort Collins, CO

Just to make sure I'm not making some dumb assumption: by focus coil, you mean the 22-11 itself, right? I remove the Thompson focus coil (the one with centering abilities), replace it with the reversed and rewired 22-11, and possibly rotate the 22-11 around the neck to tweak centering? I want to make sure I'm not getting confused by the apparently equivalent "focus coil," "focus yoke," etc terminology.

antorsae · Joined: 16 Jul 2006 Posts: 297

Yes.

I use focus coil and focus yokes interchangeably. I don't know which one is the correct term.

Joust · Posted: Thu Sep 06, 2007 7:51 pm Post subject:

Joust · Posted: Fri Sep 07, 2007 12:41 am Post subject:

here is one of Gino's new yoke harnesses.

CZ Eddie · Joined: 23 Mar 2006 Posts: 1601 Location: Austin, TX