CurtPalme.com Home Theater Forum

[nuttall_chris]

Hey CJ, any updates. Have you tried this with the 34.9KV HVPS?

[cmjohnson]

Yes, I tried it, and really I think they're good to go with 34.9 KV HVPS units with no problem.

I have a focusing problem with my testbed unit and I haven't quite figured it out yet, but in other units, the test yokes do a good job.


I have noted something important, though, and if you want to try these yokes you MUST pay attention to this:


It looks like these yokes rotate the beam somewhat. You may have to rotate the
deflection yokes in order to re-level the image. And in my test unit, the rotation
was not trivial. The image was rotated a good 20 degrees clockwise, looking at the screen.

CJ

[nuttall_chris]

Hi CJ,

I have acquired everything I need to do your Frankenyoke Mark 2 upgrade but I have one question. The picture you posted of the wiring hookup is not quite clear, there are 2 black wires and I can't tell from the picture which one goes on which pin? I don't want to hook them up backwards and fry something.

[cmjohnson]

The black wire that is beside the red wire in the harness in the top of my hand is the leftmost black wire in the board.


Also look at the markings on the board. The black wire is paired up with the red wire in the yoke, so wherever the red wire in the yoke goes to in the board, look at the
markings to find the matching wire.


There are two issues that may need work: Overall magnetic strength may be a bit
low, resulting in the magnets operating at unusual focus values.

And the available static winding field strength MAY be insufficient, which will require
the static winding to be rewound. The new wind formula for the static winding is
about 250 turns per section on the static bobbin, which gives a total of 750 turns.
The rewound coil should read 30 mH or close to it.

I haven't said much about these yokes lately because I have not completed my
tests yet and decided that they're really ready. Proceed at your own discretion.

Oh....you will almost certainly have to rotate your deflection yokes. They do twist
the image considerably.



CJ

[Joust]

CJ,
How many turns are on the stock bobin? I thought you only were adding turns to the Astig winding?
I'll wait for your Final recomendations before proceeding. My 1292 yokes are in transit from Australia.

[cmjohnson]

I unwound the bobbin and rewound it completely with new wire. (Ga. 32 enamelled magnet wire)

I had to, in order to find out how many turns were on it.

I counted 175 turns per section and calculated that 250 turns per section is about optimal.

That's all just one wind...you just move the wire to the next section after you reach
your turns count.

Pay attention to phasing and direction of wind. Mark the bobbin with wind direction,
start and end points, and wire colors.

CJ

[Joust]

Hey Chris,
Whats the progress with this project? Is it worth while?
I still have not found useable yokes. Should i still be looking?

[cmjohnson]

I don't think it's necessary to rewind the static coil as the static coil isn't part of the dynamic focusing system which is resonance dependent.

I think it's worth doing, yes. So long as you don't pay a great deal for the yokes.


CJ

[nuttall_chris]

I have done the upgrade (Frankenyoke Mark 2) on my M8500 and on the tube face there is a noticable increase in focus. 1080p test patterns are well defined and very sharp. The big limiting factor here are the lenses. I have tried HD8 and HD144 lenses. The HD144 lenses are sharper, especially in the corners but they are still not able to do justice to the super sharp image on the tube face.

I am still tweaking my setup and will post some screen shots and more info in the next couple of weeks.

Chris.

[cmjohnson]

Good deal.

Did you have to rotate your deflection yokes?

Do you have the ability to both over-and underfocus the image using these yokes?


I'm getting variable results. They vary from one PJ to the next. I'm really not sure why.


CJ

[nuttall_chris]

I only had to make a very small rotation of the deflection yokes to correct for the new coils with my final setup.

1) Initially I used the coils as is in their stock form and casings with the "tightening clamp" placed toward the neck card. This caused a sevear rotation of the raster, some odd geometric distortions and I found that I was only able to just focus. I could not underfocus (lower focus #s) but I could extreamly overfocus (higher focus #s). More focus range appeared to be possible if the focus coil could have been moved closer to the tube face, but was not possible do to the convergence and deflections yokes being in the way.

2) I decided to try rotating the coil 180 degrees, putting the "tightening clamp" toward the tube face. This didn't work as the focus coil was now to far from the tube face to allow proper focus.

3) I then opened the focus coil casing and rotated the coil inside the casing. With the rotated coil I then put the coil in the projector with the "tightening clamp" towards the neck card. This give me the magnetic orientation of attempt 2 but allows the focus coil to be as close to the tube face as in attempt 1. This produced the best results. Much less raster rotation, more focus range (over and under focus) and no geometric distortions. This setup has the coils in the same magnetic polarity as the original marquee coils. On the tube face 1080p is clearly resolved.

I hope to have my projector back on the ceiling within the week and I will post some testpattern screenshots.

Chris.

[cmjohnson]

That pretty much mirrors my results. I was hoping at first that you could just leave them in their original casings but that creates problems. I ended up putting them in Thomson yoke casings with plastic spacers holding them together, and splitting the
cover plate in half. (It's two identical pieces glued together and you don't need the inner one at all.)


CJ

[Atom]

Hi CJ and Chris
Do you have any update on the Frankenyokes.
Thanks
Andrew

[cmjohnson]

I think I've pretty much explored this as far as anyone needs to go. Transfer the 22-22 yokes into Thomson yoke housings, make the necessary cable connections, and run 'em.


Or do the same for 22-11s if you don't need astig windings.



I've sold my last PJ and it was my test bed unit. I'm done, for the time being.




CJ

[cmjohnson]

Hey, listen, guys.... I do NOT sell Frankenyokes. Please do not ask me for them. The entire purpose of this tutorial is to give YOU the information you need in order
to brew up your OWN.


Find 22-22s. Barco used them a lot. Look for the 9 pin connector. Salvage wiring harnesses as described earlier. Follow the directions. That's how you do it.


Same thing goes for those who don't need astig windings, just find 22-11 yokes as your modification candidates.


CJ

[Lyckman]

Spent last night in Frankenland, tring to adapt barco 808-yokes for the marquee. The barco yokes looks the same as the sony-22-22-yokes. So it was worth a try.

I built a nice wire harness that would plug in to the 9-pin connector at the yoke one side and to the focus board and stigmator board on the other.

It did not work.

I tried to move the yoke up and down the neck to find the correct focus spot. I even removed the convergence yoke to extend the adjustable range. No matter what I tried, it was impossible to get proper focus with the barco yokes. Surprisingly the "best" spot was far down the neck? The opposite of what I was expecting! The behauvior was somewhat the same even if the yoke was turned 180 degrees.

I did some measurements and realised the obvious reason.. the barco yokes has 1/100 of the inductance to the marquee yokes.. 0.28mH vs 28mH.

I pulled the magnetics from one of the yokes to examine its contents. It's the same concept as the sony-yokes, but the windings indeed seems smaller.

Is it possible to modify the circuit on the focus board to adapt to the lower inductance?

// Lyckman

[cmjohnson]

Please be more specific about the exact type of yokes you used, as identified by any markings or decals that are found on them.

Beyond a doubt, the 22-22 type is used on SOME Barcos and they are suitable for the
adaptation. Other types like yours are physically similar but clearly aren't suitable
for electrical reasons.

Your static focus coils could be rewound to achieve the inductance value that is needed.

IIRC, 750 turns of 34 ga. magnet wire will yield the correct value range for the static
focus winding.

CJ

[tse]

The magnet should focus the center of the picture when positioned forward, near the deflection yoke, with no current in any winding. If it doesn't it is not the correct strength (gauss). The high inductance winding is used for fine adjustment of the center focus. The other winding is low inductance. It is used for dynamic focus of the left and right side of the picture.

Scott

[Lyckman]

Specifics:





// Lyckman

[tse]

The Marquee focus board is designed to drive one high inductance winding (>1mH) for static and top/bottom focus and another low inductance winding (<100uH) for left/right focus.

You might be able to rewind your coils but if it will not focus the center with no current through the windings then it will have to be re-gaussed to do so. The static winding can only do a small "trim" of the magnetic strength.

If you take the permanent magnet core apart be very careful to reassemble exactly as original. If put together wrong the magnet can deflect the electron beam 90 degrees and it can burn a hole in the neck of the CRT. Be careful and use old tubes for experimenting.

Scott