CurtPalme.com Home Theater Forum

[cmjohnson]

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I'll look into that. Thanks.

But, first things first. Get the static focus in the right ballpark.

Please check me on this: With the stock yokes, what is the focus value at which the central focus should be the same as if you
unplug the focus yoke? I can't remember if it's supposed to be above or below 50, only that it should not be right at 50.

With the yoke unplugged, static focus should be slightly soft. That much I remember. But by how much?

I figure that the best possible way to optimize these things is to start by calibrating the coil magnets first, then calibrating the dynamic coil,
then the static coil.

Apparently the astig windings in the 1292 yokes are compatible with the Marquee astig circuitry. This seems to be adequately effective.

Probably due to the longer 1292 yoke housing, the CPC rings seem to be slightly less effective than with the Thomson yokes.

I'm almost tempted to install a flare ring set in front of the new focus yoke to help with centering. Being way forward on the neck,
it should be pretty effective. Maybe too much so.


CJ

[Nashou66]

I found every Stock Focus yolk is different. Some were under focused some almost perfect and some over focused. This was confined later by connecting them and having to increase focus, or lower it or hardly touch it. This is why they have Individual RGB focus in the service menus. Almost impossible to keep the strength of the magnets the same on all three focus packs.

The Astig windings in the KD coils have almost the same inductance as the marquee's Thompson coils.

I actually found the magnets in the Barco packs better than the ones in the sony packs.

Athanasios

[cmjohnson]

So what did you end up with as your final static and dynamic coil inductance values, after adjustments?


CJ

[Nashou66]

I just used the stack marquee values. But never tested further.

[barclay66]

Hi,

Just a little question to CJ: Is it possible to restore the now missing pictures at the beginning of the thread?
I wanted to go through all of it in order to understand what You guys are doing here...

Thank You!

Regards,
barclay66

[cmjohnson]

Since I'm now working with these again, for the short term, anyway, yes, I can make some new pics and put them up.
BUT, I would recommend that anyone who wants them for reference should save copies of them.


More information on my current status with the experimental yoke on the green tube:


Setting user focus to 50, I checked the static focus value that gives best focus and it was only about 60, which I think is quite good. I'm running 27 uH on
the static focus coil.

I inverted the polarity of the dynamic coil and the results did not change: The edges are well out of focus with a value of zero and from there as you ramp up the value it only gets MORE out of focus.

Unplugging the focus coil at this point brings the edges into commendably sharp focus and takes the center out of focus by about 10 points.


So, then I tried disconnecting the dynamic coil by pulling the green and purple leads out of the connector and leaving only the static coil in operation,
hoping that I could then get good focus everywhere.

I do have that right, don't I? The center two leads in the focus coil are the static focus coil leads?

Well, that wasn't helpful. I couldn't get good focus ANYWHERE with the dynamic coil disconnected.


I'm satisfied that the static coil is about right. I'll take the dynamic coil down some turns next and see what happens.
It seems to be overpowering, for its job.

What I AM seeing here is that the range of focus available is much larger than with the stock yokes, and once focused, it is
stable and holds sharpness at high contrast levels. This alone makes the mod worth the effort even if it will not yield better
focus than the stock yokes.

Of course there is no centering ability with these yokes. But it appears that they put the image well in the center to begin with
so that shouldn't be much of a problem.

The reduced effectiveness of the CPC rings (as they're now farther back and less effective) makes me think about modding the yoke
housings after I've got the coil values sorted out. I might even use Thomson yoke housings, modified as need be in order to work
with these. If they'll fit at all, that is.



What we're doing is simply swapping the mediocre stock Thomson yokes out of a Marquee and putting in superior Kanto-Denshi designed yokes,
which poses certain problems but also holds the promise of better, sharper, and more stable focus than the Thomson yokes can deliver.

There are a number of K-D yoke variants and not all of them are suitable for the upgrade but some are. The ones out of a Sony VPH-1292 are
sought after for this purpose, as are the yokes found in some higher end Barco projectors.

For a Marquee 8000 or 8110, you'd want yokes that only have focus coils. For the 8500 and 9500, you'd want yokes that have static and dynamic
focus coils and astig windings as well.


The potential for picture improvement is considerable. Long ago, my initial experiements using a lowly 8000 yielded focused images on the CRT face
that were sharper than the resolution ability of the HD-8B lenses to resolve. Speaking purely of what I could get on the CRT face, I was getting respectable
contrast between black and white bars (high MTF values, but how high I can't say) with the test pattern running at 2048x1536 and anamorphically squeezed,
which would equate to 2048x2048 in 4x3 full frame. The refresh rate wasn't really high and it couldn't be, because of limitations in the video amplifier
chain's bandwidth, but it did work.

I've been lazy about actually completing this project even for myself. But I'm working on it now and intend to see it through until I either achieve success or
give uo and go back to the stock yokes.

CJ

[tse]

The gauss of the permanent magnet is very important. If the static current is at 0 (disconnect one of the wires of the static winding) the image should focus about 1/4 of the way from the sides. If it is not pretty near that the magnet gauss is off. The dynamic focus current is parabolic in shape and is cap coupled to the dynamic winding so there is equal charge both negative and positive. Connection of the static winding shifts the gauss down (decreases the gauss) to the point where the center is in focus. If you have a variable current power supply you can connect to the different windings and find the current that is needed for focus in the different areas. Remember, the horizontal dynamic focus is for the center of the left and right sides and the vertical dynamic focus is for the center of the top and bottom edges not the corners.

Scott

[cmjohnson]

Scott, the yokes I'm working with are the ones that we ran through your gaussing rig about a year ago, at a guess. They magnetized to the right gauss range to be useful. That part, I think is fine.

With the focus plug disconnected, the point of best focus is right about where you say it should be.

I have not yet had a chance to adjust the dynamic winding. I think it's just way too hot and I need to take some turns off it.


As long as I have your attention, is VDC ready to dispose of any of the specialized items associated with Marquee manufacture yet, including parts
inventory of parts that are rarely if ever ordered as replacements?


CJ

[km987654]

I have just tried a static 1292 focus yoke with the PJ I am building to see if it does any better than the focus yokes from the BG808s. I have Sony 9" tubes in a BG808s.

I tried the red and green tubes only as I am not too concerned about blue.

The red tube showed a definite improvement in the centre of the image (where you would expect) but the green was no better.
The 1292 yokes seem to operate in the reverse to the barco units. The 1292 focus better the closer to the deflection yoke and the barco units focus better further away. That was the trouble with green as the focus got better the closer to the deflection yoke and you hit the deflection yoke before its as sharp as the red with the 1292 yoke.

I have read through this thread a couple of times but it doesn't quite go where I need it to.
I was thinking of removing the coils from the barco focus yoke and putting them into the 1292 yoke. The units are physically almost the the same from the outside but would this work does anyone have any advice?

[Nashou66]

They wont work electronically. Also Barco reverses the magnet structure on the green so the North and south are 180 degrees from the red and blue coils.

This mod is basically only for a marquee as their focus coils are totally different in design than all other yokes which mostly use the Kanto Denshi design.

Athanasios

[km987654]

[bpdski]

I recently acquired a set of Frankenyokes and was interested in putting Molex connectors on them without sacrificing my original Thompsons. I figure if I run into trouble or they don't work right I can put the originals back in my 9500. This also allows me to hopefully minimize the time my projector is out of service by having the new yokes ready to go. I was able to find the correct parts after doing some searching and wanted to post the links here in case anyone else would this useful.

Here are the 4 and 6 pin housings
http://www.mouser.com/Search/ProductDetail.aspx?R=09-50-8040virtualkey53810000virtualkey538-09-50-8040
http://www.mouser.com/Search/ProductDetail.aspx?R=09-50-8060virtualkey53810000virtualkey538-09-50-8060

Here are the crimp pins that go in the housings, I would buy a few extra
http://www.mouser.com/Search/ProductDetail.aspx?R=08-52-0125virtualkey53810000virtualkey538-08-52-0125

I've attached a picture of my yokes as well, I got fancy and put color coded wire braid over each harness. The other wires in my projector have these too. They look nice and keep wires from getting pinched

[htguy1]

Hi,

Is there a thread somewhere which has the most update assembly and setup instructions for this mod? Saw a 4k JVC and decieded its STILL not worth the money cause our PQ is still right there with them in many aspects.

Thanks

God bless...
Mark

[redfox001]

I think this page has the Frankenyoke Wiring.doc

http://www.curtpalme.com/forum/viewtopic.php?t=2498&postdays=0&postorder=asc&&start=420

From what I read this version should be ok for the 1292 yokes in a 9500?

I understand that these yokes with the correct wiring should not be modified or changed in direction on the tube? I attached the doc.

[htguy1]

Hi,

I just realized that i have ksd26 yokes for my frankenyoke project anyone have info for using these?

Thanks

God bless...
mark

[cmjohnson]

Hi again, guys. I'm back, at least for a little while.

I've decided it's time to once again take a shot at trying to still further optimize my yokes. I've actually been running the stock yokes for some time but decided that since I have to do some bellows and glycol replacement (got murky in two tubes, plus a slow leak in one) that I would go ahead and finish out this long-dormant project while I'm at it.

My goal is to optimize one set of yokes specifically for best performance at 1080p-60Hz.

I recall that when I wound my test yokes, I had used the calculated values for it and the yokes ended up being TOO powerful for the job. So I started to take turns off the windings. I abandoned the project before I'd found the ideal values.

I intend to take another shot at it and this time at least complete the experiment with one yoke to start, and if I can get it to deliver optimal results, measure its parameters and then publish them here. And adapt two more to the same specs.

At that time I'll then offer out my stock of spare candidate yokes and parts to someone who's interested in them.

I only want and need one good set of them. Pass the rest on to somebody else for playing.

[htguy1]

[redfox001]

[cmjohnson]

I have no experience with any Barco yokes that had astig windings.

I've been focusing only (pardon the pun) on 1292 type yokes in fairly recent times. I think they have the best chance
of becoming truly optimal (and available) of any I've tried yet.

If it's a big fat yoke with the 9 pin modular connector on it, it's probably worth trying. Check static focus first.
It should give close to good focus with it just sitting there on the neck and connected to nothing. As TSE said.
Refer to his notes for the raw truth about where static focus SHOULD be.

[redfox001]

Ok I have here Sony 1292 yokes and I have Barco 809 yokes that are for 9 inch tubes but only 4 pole astig. I am thinking about trying these Barco first.