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Marquee focus improvement project
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cmjohnson




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


PostLink    Posted: Wed Jun 29, 2016 1:24 pm    Post subject: Reply with quote


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I've done my first round of tests with a KF-3212 focus yoke and after sorting out some issues with the wiring and also with traces breaking away from the interconnect PC board in the focus yoke assembly, I was able to get one running in the test Marquee.

There is not a lot of focus range available. You simply can't dramatically over or under focus the image. All you can do is fine tune it. From slight soft to razor sharp, not from fuzzy overfocused blob to fuzzy underfocused blob like you can with the Thomson magnetics.

But there's enough. If you position the coil correctly, there's enough range to get the job done, and one beneficial consequence of having a smaller range of focus adjustment is that within that range, focus adjustment steps are very small and precise.

So, I'm going to call THAT a success, or well enough, for the moment, and move on to something else.

That'd be another look at the KF-3203 yokes. I had made up some for a Marquee a few years ago but had problems with the one I chose to use for testing.

So I checked the wiring. Sure enough, broken trace. Rewired it, fixed it, ran it.

It's effective. It has more focus range than the 3212 type. But I haven't even looked at what can be done to optimize a Marquee for it yet.

VERY interestingly, the 3212 and 3203 coils are magnetically out of phase with each other.

So my findings at this moment are that either the 3212 or 3203 coil types can be run in an otherwise unmodified Marquee,
but you will have to physically move the coil up and down on the tube neck for best focus. I recommend setting the user focus to 60, the service focus to 50, and adjusting the yoke position for sharpest focus under those conditions. That seems to work well
for either type of focus yoke.

Still deciphering the G90 focus yoke. No tests have been done on those yet, as a result.


Also looking at ways to tame the mighty G90 deflection yoke. Need to reduce drive levels in the HDM.
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cmjohnson




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


PostLink    Posted: Thu Jun 30, 2016 1:46 am    Post subject: Reply with quote

I just want to reiterate, the objective of this project is to achieve improved focus STABILITY over a wider range of contrast levels.

I do not really expect that any focus yokes I'm trialing will actually take sharpness to another level. The Thomson yokes focus to pretty close to the electron beam size limitation already. They're just not very good at retaining that level of sharpness as you push the contrast levels up past 60.

I've found that the general health of the LVPS plays a role in focus stability with the Thomson focus yokes, as I had serious blooming issues at higher contrast levels, blooming issues that went away when I put in a newer, healthier LVPS after my original onne died.

But even then, the KD focus yoke designs are superior, at least when correctly implemented with appropriately adapted driving electronics.


I found some mistakes in the assumed wiring for the 3203 yokes, and once I corrected them, I've found that the 3203s work much better and give a very reasonable and sensible range of focus. I'm VERY close to giving the thumbs up.

They want to be right up against the Thomson deflection yoke assembly, but want to be spaced slightly away from a G90 deflection yoke. I think it's pure luck that they can reach the point of sharpest focus with the Thomson deflection yokes.
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cmjohnson




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


PostLink    Posted: Thu Jun 30, 2016 3:38 am    Post subject: Reply with quote

This experiment has shown me some very interesting things, including some insights into the minds of the designers of various projectors.

I find it endlessly interesting that between the Marquee, G90, and Cine 9, such things as simple as the deflection yokes are radically different and represent three different schools of thought.

While all three deflection yoke assemblies are pretty similar, in the respect that they all have the same equivalent coils doing the same equivalent jobs, and are used in projectors that all are designed for the same general level of performance, they're very different in many functional respects.

The Barco deflection yoke's two horizontal windings are permanently connected together in series. (Soldered at the midpoint.)

The G90's deflection yoke's two horizontal windings are brought out in parallel, each with its own pair of connections. In the projector, they are always run in paralle.

The Marquee's deflection yoke is wired similar to the G90 yoke, but the projector chooses series or parallel wiring by connecting them together one way or another by relays on the HDM, determined by scan rate. Which is the most versatile way of doing it,
and, I think, the most efficient as well.

The G90 deflection yoke is a power hog. But the G90 is a power hog. I've got a set of G90 circuit boards and frankly they're stunning, awesome pieces of engineering. I wish I had a full G90 chassis to do a full comparison against, but based on the circuit boards alone, it looks to me like Sony's engineers were pretty much told to build the best projector they could, without any cost, weight, or size constraints.

With not less than 34 individual circuit boards (including daughter boards) in a G90, vs. about 18 in a Marquee, the G90 makes
the Marquee look cheap (and very simple!) by comparison. But I can lift and move a 9500LC from one bench to another by myself. (Not recommended, though!) No way I can do that with a G90.

When you look at a piece of electronics, you are looking at the physical manifestation of the thought processes of the designer(s).

The G90 tells me that Sony's designers are MAD. In a very good way. Totally into making the highest quality machine they know how to make, and to heck with convenience, saving weight and size, or budgetary constraints. The Marquee is clearly an expression of competent, innovative engineering done by people who are cost conscious and like to make things that are simple, serviceable, and reliable.
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cmjohnson




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


PostLink    Posted: Thu Jun 30, 2016 4:36 pm    Post subject: Reply with quote

So at some point, someone here is going to decide they want to try something like I'm doing for themselves.

I am going to help you with that. With the understanding that what I show you is a work in progress, and perfection has not yet been achieved.

I'm going to start with the focus yoke system because that's the primary reason for this whole project.

The Marquee focus connector has six pins. We really are most concerned with just four of them.

Using the stock focus yoke as our reference for wiring color codes, pins 1 and 2 are the dynamic winding, pins 3 and 4 are the static winding, and pins 5 and 6 are the thermistor sensor wires.

1 is orange
2 is yellow
3 is black
4 is red
5 is brown
6 is green


I have always pretty much ignored the thermistor sense wires, the brown/green pair, but if you were to actually install a suitable
thermistor on the yoke you want to use, it could be beneficial and help focus to remain stable as the projector warms up. But
that's for you to decide. I shall not mention the thermistor system again.


You're going to need cables for your yoke project and since I have an abundance of stock focus yokes, I just clip the cables off
the yoke, right next to where it enters the casing. I also take the brass screws and wing nuts, they'll be used to secure the casing
of the yoke you want to use.


You can either sacrifice a stock yoke for the connectors and cables, or you're on your own to find suitable cables and connectors. I'm not going to tell you how to make a cable.

I'm also not giving soldering instruction classes. I presume you know your way around a soldering iron and know not to pick it up by the hot and/or pointy end. If you don't, I recommend you don't attempt this project.


First, I remove the shells from the KD focus yoke. It's secured with three copper rivets. Get them out by any means that suits you,
I may drill, I may use diagonal cutters to nip the flared end off, I may push them out with a hot soldering iron. Whatever works.

The holes will need to be slightly enlarged anyway to accept the brass hardware taken from the stock focus yoke. Or get other hardware, but do NOT use magnetic hardware. Stainless steel or brass. Check the stainless steel with a magnet to be sure it's not magnetic. Some grades of stainless steel are magnetic.

With the shells off, carefully remove the core assembly and the small connector PC board along with it. Be careful not to damage
any wires.


Now, you want to REMOVE THE WHITE CONNECTOR. Use desoldering braid or a solder sucker, and get the solder off, and carefully remove the white connector.

Why? Because this is MUCH easier and more reliable than any other method. Even if you have a cable with the mating connector on it, and it's long enough, it's still labor intensive to adapt the other end of the cable to plug into the focus board. But you can do that if you want to. I just don't bother with that.


Refer to the first photo. It shows two of these little connector boards, one with the connector still on it, one with the connector removed.

These boards were taken off yokes that were extensively modified, years ago. I do NOT recommend that you completely remove your boards from the yoke assemblies. It isn't necessary.

Let me back up for a moment. Before touching anything, document everything. Take photos or make drawings of every wire connecting to that board so if one does break, you know where to reattach it.


OK, great, we've got a cleaned, desoldered board with no connector on it. Now what?

Now is a good time to look at the board carefully and make note of the markings on the brown side. They are very informative and will guide you in attaching wires where they need to go.

Refer to the photo of the connector board all by itself, clearly showing the markings.


From RIGHT to LEFT, that's pins 1 to 9 in that order, you have:

Ground (we will not use this wire)
4X- (4 pole astig winding, X axis, - wire)
S- (Static focus winding, - wire)
4X+ (4 pole astig winding, X axis, + wire)
S+ (Static focus winding, + wire)
4Y- (4 pole astig winding, Y axis, - wire)
D- (Dynamic focus winding, - wire)
4Y+ (4 pole astig winding, Y axis, + wire)
D+ (Dynamic focus winding, + wire)

We'll worry about the astig windings later.

So, by looking at this, we can see that the focus windings will attach to connections 3, 5, 7, and 9.

Static windings will attach to 3 and 5.
Dynamic windings will attach to 7 and 9.

Static windings are red and black.
Dynamic windings are yellow and orange.



So, how to attach these wires? Strip them back, stuff the wire through the hole, and solder them?

Actually, no, I don't recommend doing it exactly like that because these little circuit boards have fragile traces,
easily lifted and easily broken. I've had WAY too many of them break traces just from the stress of light handling
after trying to attach the wires in that method.

So what I do now is I use a small drill and DRILL OUT THE HOLES, to a size that allows the wire WITH its insulation
to pass through. The wire takes a 90 degree turn and then is soldered directly to the solder connections on the
other side of the board. Refer to the photo showing the colored wires attached.


There's a fourth photo showing the back and front of the boards. This is there to show you that the wires run straight across without crossing each other. They're one for one, ground is ground at 1, 4X- is the second wire, S- is the third wire, etc.


For the astig windings, blue and grey is one pair, purple and white is the other pair.

Attach them as per the photo.


A note on phasing: I'm not guaranteeing that ANY given pair of wires is correctly phased. I know the dynamic winding wires need to be the orange and yellow ones leading to the focus board. I know the static windings need to be the red and black wires leading to the focus board.

I do not guarantee that you shouldn't exchange red for black, or orange for yellow, or purple for white, or blue for grey.

You can experiment. But I have already done those experiments and I have found that, yes, phasing does make a difference. Especially on the static winding. (red and black wires) Phasing also makes a difference on the dynamic winding but not as much.

I have found that when using the 3203 yokes, after you've wired them up correctly, the procedure for adjusting for best focus is NOT THE ONE IN THE MANUAL.

I state that again, for clarity's sake:

WHEN USING THE KD 3203 FOCUS YOKE, THE PROCEDURE FOR ADJUSTING FOR BEST FOCUS IS NOT THE ONE IN THE MARQUEE MANUAL.


Here is the procedure that I have developed:


For the initial tests, I removed the lenses. This is so you can reach into the projector without stretching
and maybe getting shocked. I reattached them after getting yokes running well enough that I want a closer, more detailed look at the CRT face to really chase the focus.

While it IS safe to touch GOOD condition anode leads, they still can build up a static charge on their outer skin which can give you a shocking surprise. It's not directly harmful but if you jerk in surprise, who knows what you might hit as a result? That being said, I've never once been jolted by an anode lead, not even from static buildup on its skin. I've been hit by static charges in other parts of the projector.
------------------------------------------------------------------------------------------------------------------------------
I'm going to take a break and address that issue right now: GROUNDING STRAPS.

They're EVERYWHERE in the Marquee chassis and they're all there because they HAVE to be there!

The CRT, you see, is a big freaking capacitor. One of the characteristics of a capacitor is that if you apply a voltage
to one side of it, an equal but opposite voltage will develop on the other side of it.

The anode lead delivers a murderous (literally!) minus 34,900 volts into the inside of the CRT. Thus, the CRT, being
a capacitor, will TRY to develop a positive charge of 34,900 volts on the outside glass. But that would be very bad,
for that to happen. Arcing would occur, electronics would fry, technicians would die.

So there's a conductive paint called "dag" (short for "aquadag)" which is applied to the back of the bell of the CRT,
and to it are attached some conductive copper strips with ground leads on them. In a Marquee, those two ground leads
attach to that central grounding plate on the back of the neck card. From there, grounding is achieved via the white ground
leads that attach to the neck card shield cages. AND from there, via those roughly 5" long braided straps, they attach to the rear heat sink, thus making a path to chassis ground.

This whole system has to be intact for the safety ground system to work!

IF you fail to connect this whole system, after the projector has been running for some period of time, maybe a minute, maybe five, maybe half an hour, eventually at some point a static charge builds up that reaches the point where it jumps over to something that is grounded. You will hear a sharp SNAP and the picture instantly goes out due to the arc detect circuit.

The picture will come slowly back up as the anode lead recharges that capacitor we call the CRT. If you're watching the tube face while this occurs, it's very interesting as you will directly see the effect of how varying the anode voltage affects the picture. As anode voltage increases, the picture becomes smaller, brighter, and comes into focus. It's a neat little electronics and physics experiment all by itself!

It's HARD to replace magnetics without the whole ground system connected.

I have an alternative method. I directly connect the CRT ground straps to the chasis, using some small cables I made up
with a ring lug on one end and a spade lug that fits the ground strap spade terminals. I screw these short cables to
the chassis using existing screws (back one out, stick it thru the ring lug, screw it back in) and by doing this I have
directly grounded the CRT shells and don't really need the rest of the ground system as much. It allows me to work
with fewer obstructions.

---------------------------------------------------------------------------------------------------------------------------------

And now back to the focus procedure. AFTER you have ensured that grounding straps are in place and working properly.


Set ALL focus settings to 50. User focus to 50, service focus to 50 in the center and in every zone.

DISCONNECT the focus coil from the focus board. Yes, you can safely plug in, and unplug, the focus plugs from the focus board, but be careful not to miss when you put the plug back in. If you're off by one pin, the plug will still go on but it can damage the focus circuit.

Now, with the focus grid pattern displayed, move the focus yoke back and forth on the neck until the OUTER EDGE of the pattern is in perfect focus.

Plug the focus yoke in.

Expect the whole picture to go slightly out of focus.

Adjust center focus for sharpest possible focus. It should be at 50, give or take 20 points at most. If it won't focus between 30 to 70, something may be wrong. I've never had one be that far out yet. Not when you use this procedure as I've described it so far.

Do understand, though, that the strength of the permanent magnets in the focus yoke are a very big part of the overall picture. If you have one that has been knocked around, thus causing it to lose magnetic strength, (yes, some magnets will lose strength if you drop them.) then you might have a focus yoke that's too weak to ever work. Getting it remagnetized to the proper level is possible and I may be able to arrange to get your focus magnets adjusted to the proper strength. PM me about this. (The service is not free.)

If the center focus is not more than 60 and not less than 40, (gently) tighten down the clamping screw on the focus yoke, because you're probably right where you want it to be.

Now perform the dynamic (outer zones) focus. Don't worry if you achieve sharpest focus at zero or 100 or don't see much happening. I have found that with these yokes, dynamic focus is pretty subtle. But who cares as long as you can reach sharpest focus?

IF you can't reach sharpest focus on the outer zones, get them as sharp as you can and then loosen up the focus clamp and move the yoke until they DO sharpen up to best focus. Then restart the focus procedure and see where center focus ends up. If it's not more than 80 or less than 20, and you've got a good sharp image from corner to corner, call it a success and don't worry about it. Results matter, more so than how you get them.

Still having trouble? Try out that focus yoke on a different tube, complete with using its proper focus channel. You MIGHT have a weak channel on the focus board. See if a stock yoke works properly on the same channel. If the stock yoke works properly, both static and dynamic focus, then the focus board is probably fine.


There is no denying it, there is some degree of educated guesswork to getting best focus from these yokes. AND I have found that they respond differently depending on what deflection yoke is being used. Yes, you read that correctly.

My attempts to use a Barco deflection yoke have not yet been successful. Their impedance is very low and the Marquee
HDM doesn't like them. I can fix that but I'm still figuring out how to mod the HDM to do it.

The G90 deflection yoke seems to play very nicely with the 3203 yoke. But the G90 yoke isn't ready yet, either, since
it draws too much current and can't be run in the green CRT channel because the HDM will complain. (Only the green
channel of the HDM has a current sense circuit. So I can run G90 deflection yokes in red or blue, though even then, the raster is still too wide and the HDM needs a mod for that, too.)

Focus retention with varying contrast levels has so far been excellent using the 3203 yokes.

So far I'm not so happy with the 3212 yokes. They work but they're "subtle", not giving me the range of focus that I expected. Those are a work in progress, while I consider the 3203 yoke to be mostly a success. I'm not going to say that there isn't more room for improvement and optimization, but I find that they work well IF they're wired up correctly and all the phasing of the wires is correct.


That's enough for one post!



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cmjohnson




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


PostLink    Posted: Fri Jul 01, 2016 3:46 am    Post subject: Reply with quote

For the first time that I am personally aware of, a Marquee is now running G90 magnetics, including both the deflection yoke and the focus yoke.

It's not "ready for prime time", so to speak, but it's running.

The picture is sharp from corner to corner. No modifications to any Marquee electronics have YET been performed.

Range of focus is good. Focus retention at higher contrast levels is excellent as predicted.

Dynamic range of adjustment (the outer zones) when using ANY focus yoke other than the Thomson yokes has not been observed to EVER be as broad as the adjustment range available when using the stock focus yokes. I can't explain that yet!


The electrical values of the G90 yokes are sufficiently different that I believe there will be some benefit to optimizing the capacitor values on the focus module. Though they're not BIG differences, going from 31 to 39 µH is a significant change that warrants some cap value adjustments.


The difference between cap values would be, for example, to change the unswitched capacitor from a .033 µF capacitor to a .039 µF capacitor, and to change that big 2.2 µF capacitor to 2.5 µF.

Changes that small would be implemented by just strapping smaller capacitors across the existing ones.
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barclay66




Joined: 27 Jun 2011
Posts: 1291
Location: Germany

TV/Projector: Marquee 9500 Ultra


PostLink    Posted: Fri Jul 01, 2016 8:12 am    Post subject: Reply with quote

Hi,

You might find interesting stuff in this thread: http://www.curtpalme.com/forum/viewtopic.php?p=437318&highlight=#437318

Regards,
barclay66
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cmjohnson




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


PostLink    Posted: Fri Jul 01, 2016 1:55 pm    Post subject: Reply with quote

Cool, thanks for digging that one up. More information dug up to add to the files.


Now that I have the G90 focus coil operating in a Marquee, I have a serious desire to get on with the HDM modifications
that will allow me to run the G90 deflection coils. I believe my answer lies on the HDM's daughter board.
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cmjohnson




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


PostLink    Posted: Wed Jul 06, 2016 7:29 pm    Post subject: Reply with quote

I found the resistor that conitrols overall H. width and by suitable value changes have managed to put the raster width range right where I want it.


It's R175, it's on the HDM underneath the daughter card. Normally 357 ohms, increasing its value decreases the overall scan width.

I found that changing it to about 800 ohms (809 to be exact, because that's what I had available in this range) was just about perfect.


But it's still drawing too much current and can't be used in the green channel.

So I'm experimenting with putting series inductors into the yoke circuit to try to bring the sensed inductance into the range where the HDM should be happy.

The G90 deflection yoke only measures 80 microHenries per coil. (X2) The Thomson yoke, 280 microHenries per coil.

So that's a total shortage of 400 µH (very closely) that we need to keep the HDM happy.

As luck would have it, I have some 120 µH medium current inductors in my parts bins. So I tried tagging one onto each of the four leads,
thus adding about 240 µH to each coil which is a bit too high but it's OK for test purposes.

And the projector powers up and displays an image with the G90 yoke connected to the (modified) green circuit.

Wonderful.

BUT...raster width is way down. Yeah, sure, it would be. We're throwing away so much power in four inductors plus the deflection yoke,
who would be surprised that this would shrink the raster width?

So I reverted the H. width setting resistor R175 to its original value. (357 ohms.)

The raster width opened up slightly but not enough.

I can see now that if this is going to work at all, I'm going to have to find a happy medium, where the yoke plus added inductors
provides just enough inductance to keep the current sense circuit happy, and adjust the width resistor to get the required width
without overdriving the amplifiers.

I concede the possibility that it may not be possible to satisfy both conditions at once. Consequences would be an unusably small raster
or a roasted HDM.

I knew this was a possibility. I'm hoping that the values can be juggled to achieve success.

Another possibility is to improve cooling in the HDM (add a fan or two at the ends of the HDM cage) and modify the current sense circuit
to be more permissive. There are obvious hazards to this approach if it's handled too aggressively.
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cmjohnson




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


PostLink    Posted: Wed Jul 06, 2016 7:53 pm    Post subject: Reply with quote

Update to the above: I've found thatI can get the unit to run with at little as 120 µF of added inductance on the coil if it's added at the right spot on the HDM.
Which is within reason.

I need to get a few more inductors in various values so I can fine tune the needed mods. The goal is simply to use as little added inductance as is necessary in order to make the current sense circuit happy.

Knowing that the answer is maybe under 100 µH of added inductance is happy news. I am more convinced that running G90 deflection yokes is feasible without
extensive mods to the projector.
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cmjohnson




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


PostLink    Posted: Thu Jul 07, 2016 1:01 am    Post subject: Reply with quote

I think I need to document this here:


I found in my inductor experiments that if I don't balance both coils in a deflection yoke with the same values of inductors, then raster ringing is present and it is dramatic.

This suggests to me that one of the possible causes of raster ringing is likely to be an imbalance in inductance between the two coils.

This suggests that it should be possible to balance a deflection yoke and eliminate raster ringing entirely (IF it is caused by coil imbalances) by adding a small variable inductor, better yet a pair of them one of them connected in series, one per deflection coil. Tune the variable inductors until the raster ringing goes away.

I'm going to try it. Once I find some suitable tunable inductors to use.
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cmjohnson




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


PostLink    Posted: Wed Jul 13, 2016 5:37 pm    Post subject: Reply with quote

Currently I'm making up a test board to allow me to quickly swap around components under test and not have to unsolder and desolder parts from the HDM. Solder traces only last so long. Keep soldering and desoldering them and they'll break and fall off.

Once I've got some good values established I'll do those mods on all three channels and begin more serious testing.
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cmjohnson




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


PostLink    Posted: Mon Jul 18, 2016 9:10 pm    Post subject: Reply with quote

Still figuring this out. I'm thinking a more efficient way to run the G90 deflection yokes is to install a matching transformer
rather than throw away power with series inductors.

I'm looking into the transformer requirements and trying to find suitable types for experimentation.
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mp20748




Joined: 12 Sep 2006
Posts: 5681
Location: Maryland

TV/Projector: 9500LC Ultra / Super 02 and 03 VIM


PostLink    Posted: Tue Jul 19, 2016 1:55 pm    Post subject: Reply with quote

This is why I sold my Frankenyokes and gave up on working on the focus circuit to improve the focus on my Marquee.

I've been working on a special neck board (commercial project) that required changes be made to the Beam Limit Circuit and a few other other areas as well. The 02 VIM that's being used here does not have peaking (none). That is the only change on the VIM, with the neck boards being a five month work in process. I had to figure out the Beam Limit on my own, that is supposed to be done only to the Green CRT, but I will apply to the Blue and Red as well. I have some testing to do to make sure I have this Beam Limit right. Other than that I think I'm nearing getting these ready to ship to west coast next week, hopefully in time.

I have the cameras pointed directly into the lens and I'm using my pattern generator with a 3' RGBHV cable from the generator to the RGBHV Card in slot2. The Marquee has stock focus coils with no special focus mods or changes made to the focus circuit. The camera could be better though because it still looks better looking on the tube itself.

These special modified boards are NOT to be used in HT. Just posting to show focus


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cmjohnson




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


PostLink    Posted: Mon Oct 03, 2016 3:12 pm    Post subject: Reply with quote

Update on this:

I now have a G90 in the house which I'm retubing now. Blue was broken, green has too much wear for me to keep it, red isn't far behind and I have absolutely no shortage of new red tubes.

My experiments have identified a need for a transformer to be placed between the Marquee HDM and a G90 deflection yoke for everything to run right. I've submitted the design requirements for the transformer to a manufacturer not far from me that can complete the design and build me a few prototypes.

That will handle the impedance mismatch between the HDM and the G90 deflection yoke, allowing me to run that yoke in
a Marque. Which is important, because the benefit of the G90's focus yoke is only optimized if it's run with the deflection yoke it was designed to work alongside. They're designed as a system, and work better together than mixing and matching.

Reportedly, and I will soon be able to measure this for myself, the G90 focus yoke does yield a smaller spot size than other focus yokes. Particularly smaller than the Thomson yokes.

So, when my transformers are made, I'll be able to test run a G90 magnetics stack in a Marquee.


I was also looking into the idea of building a 12 channel variable current power supply system so as to be able to run the G90 electronic CPC rings in a Marquee but since I started thinking about that, I have learned that Sony's implementation of that
system is a dynamic system, allowing 9 zone controllability of the CPC adjustments, just like focus and astig.

I can not replicate the precision of an active system like that using only static DC power inputs. All that can do is replicate
the function of a good set of CPC magnets.

So I'm discontinuing that line of investigation as I can't see that spending the R&D money on a DC CPC drive system is
going to give better results than a low cost set of passive magnets and I have plenty of CPC magnet sets.


This will unfortunately pretty much guarantee that a Marquee with G90 magnetics including the deflection transformers will probably not be able to exactly match focus sharpness in the corners as I can't match the dynamic CPC system in a G90

But I do fully expect an improvement in focus with the G90 deflection and convergence yokes adapted and running in the Marquee.
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htguy1




Joined: 30 Jul 2008
Posts: 99



PostLink    Posted: Thu Oct 27, 2016 8:29 pm    Post subject: Reply with quote

Thanks for sharing all your work on this CM! I look forward to the final results!
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cmjohnson




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


PostLink    Posted: Fri Oct 28, 2016 2:57 am    Post subject: Reply with quote

So do I. But I have not heard a peep from the company I contacted regarding the matching transformers.
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