Can one "overclock" a CRT monitor's video input bandwidth? Need slightly higher refresh rate than my existng CRT allows...

Ken, good quality CRTs are going for next to nothing on eBay and just about everywhere else. With a little searching (e.g. company moving/going out of business/etc sales are great for this) you should be able to knock that $250 down to under $100. Trying to increase the bandwidth on your existing CRT will cost MUCH more in component cost and soldering time.

I'm assuming that you have a modern CRT with microprocessor controls that displays "signal out of range" or words to that effect when it gets a signal that is beyond its rated capabilities and your intent is to alter the limit beyond which that signal appears.

To do that you'd have to reprogram the control processor, which means identifying it, finding the firmware ROM, pulling the program off of it, disassembling it, analyzing it, and then figuring out how to tweak it to make the change you want.

This would be weeks or months of work for a professional programmer familiar with that particular processor's assembly language--coming in cold you're going to have to learn that before you can do anything, and if you have no programming experience assembler is generally not the best place to start learning. You'll also need equipment that costs about the same as a new monitor to be able to read and reprogram the ROM.

And once you've done that the analog components that actually do the work are not going to be up to the task of handling that bandwidth--you'll get any of several kinds of image degradation.

If you are _paying_ somebody to do this then the cost is going to be enormous. By the time you're done you'll likely have paid enough to get a containerload of new CRTs.

If you've got a hundred thousand machines out in the field all with the same monitor and you want to try working up a mod for the monitor rather than replacing them all then this _might_ be worth trying with the understanding that there is no guarantee of a successful outcome, but even if the mod itself is completely successful there opening each monitor and replacing the ROM is likely to come perilously close to the cost of a new monitor.

For just one monitor, the only justifications I can think of for doing it are that you want to learn something for your own satisfaction, you just plain enjoy dinking around with such things, and neither of these is a sound business reason.

--
--John
to email, dial "usenet" and validate
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No, there is no practical way to do this without extremely extensive reworking of the circuit design and components. This is NOT practical even for people who work on high- voltage CRT circuits all the time, much less for people like us who only dabble.

The major limiting factor is the horizontal sweep frequency, and then the frequency response of the video path. The second of those factors COULD be modified to get higher frequency- response, but boosting the horizontal sweep frequency is just not practical for most people. It very likely would involve modification or replacement of the two most critical components in the whole circuit (the deflection yoke and the flyback transformer).

Richard Crowley in rec.video.desktop Note that this is not really on-topic for r.v.d which is chartered for discussion of television editing, which appears to have nothing to do with your question. Hopefully, you will get more expert advice from one of the more on-topic newsgroups.

There are literally tons of free, good used monitors out there for the asking. I picked up seven of them last Thursday at one place. They were the last items from this year's upgrades. That office maintains a little over 1000 PCs all over the county, and replaces 200 older working systems every year, along with some upgrades. I requested 100 complete computer systems from next years upgrades and was told they would call me when they started again in the fall.

One of the monitors I picked up is a HP 1130 Professional Monitor which is a 21" monitor:

Featuring cutting-edge FD Trinitron® technology, the HP p1130 CRT monitor delivers the ultimate in image quality and user comfort. With resolutions up to 2048 x 1536 and no image flicker, this monitor is ideal for graphics-intensive applications including desktop publishing, design, engineering, software development, image processing, and digital content creation as well as general office applications such as spreadsheets and presentations.

(The above excerpt from the HP website file: hpP1130DataSheet.pdf)

BTW: It also has a second video input and front panel switch to use it with two computers or video cards. I will be using it to write code on so I can display more information at once.

--
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prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

On 4/19/2006, Ken Moiarty posted this:

Another thought: is there a video card that would be able to create the desired signal?

One might have to hack the video card's firmware as well as the monitor's.

Sounds like fun to me...well, maybe not.

Just curious - Gino

--
Gene E. Bloch (Gino)
letters617blochg3251
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'Ken Moiarty' wrote, in part: | My 19" Viewsonic A90's vertical refresh rate peaks out@ 100 Hz for a | resolution of 1024 x 728. For stereo 3-D video viewing purposes, I need it | to display at this resolution at a bare minimum vertical refresh rate of | approximately 120 Hz (though preferabley when I get another monitor, at | about 170 Hz). . | Is there any way to over-ride the monitor's built in refresh rate limitations | (e.g. by tweaking some knobs at the back, or even inside, or by making | simple modifications to a component(s) -only of course with the guidance | andasistance of a licensed monitor technician due to obvious safety | reasons)? _____

Your question posted is 'Can one "overclock a CRT monitor's video input bandwidth?' with the qualification of 'Need slightly higher refresh rate than by existing CRT allows...'.

First, changing the VERTICAL refresh rate changes the HORIZONTAL rate. The horizontal rate for 1024 X 728 at 100 Hz vertical refresh is just a bit more than 728 X 100 = 72,800 Hz; the horizontal rate for 1024 X 728 at 120 Hz vertical refresh is just a bit more than 728 X 120 = 87,360. The real limiting factor is the horizontal rate, it is a high power circuit that drives magnetic coils to sweep the electron beam from side to side. The same circuit also develops the high voltage (15,000 to 20,000 volts) power to accelerate the electrons toward the screen.

So it is not just the frequency response of the video amplifiers, which, except for the final driver stages, run on milliwatts. It is a question of the horizontal sweep circuits that account for 90% of the power used by a CRT monitor. It is not a question of cooling, it is not like overclocking a CPU or display adapter - it is more like trying to drive a Trabant at autobahn speeds.

You might try 1280 X 720 at 120 Hz; 720 X 120 = 86,400 Hz horizontal sweep rate, a bit lower than 1024 X 120 Hz. I tried this setting on my Viewsonic A95f 19" monitor (I had to uncheck the 'Hide modes this monitor cannot display' box on the 'Monitor' Tab reached clicking on the 'Advanced' button on the display properties sheet. It works at 1280 X 720 at 120 Hz, though the screen needs quite a bit of adjustment and the images are not as good as on the same monitor at 1600 X 1200 at 85 Hz.

You can also run the display card/monitor at a lower vertical resolution say

960 X 600 at 120 Hz; 600 X 120 Hz = 72,000 or 1088 X 612 at 120 Hz; 612 X 120 = 73,440. Both of these resolutions have lower horizontal refresh rates at 120 Hz than 1024 X 768 at 100 Hz. (Uncheck the box 'Hide modes this monitor cannot display.

My Viewsonic is protected from unreasonable horizontal rates - at a setting of 1024 X 768 at 120 Hz no image displays until after the 15 second time out and the display adapter reverts to the previous good resolution and vertical refresh rate. I assume your model is also, so give it a try, and let us know the results.

Phil Weldon

I can dial up pretty much any sync rate I could desire from mine

I'm not sure if S3 was the first to come out with programmable clock chips, (in the early 90s) but now pretty-much all video cards allow the pixel clock to be varied in reasonably small increments (smaller than 1%), and the horizontal and vertical clocks are derived from the pixel clock and provide a further opportunity to fine-tune the sync rates.

SVGATextMode (a neat linux app to tweak video clocks for text mode displays) can be compiled for dos (with a little work). nothing much else uses the card's firmware...

Bye. Jasen

Well I think I get the gist of the answer to my query: "There's no point". Based on all (which I didn't know until now) that would be involved, I can of course only agree.

Thanks all, Ken

'Ken Moiarty' wrote: | Well I think I get the gist of the answer to my query: "There's no point". | Based on all (which I didn't know until now) that would be involved, I can | of course only agree. _____

Thanks for replying. Do try one of the modes I suggested and let us know your results with the Viewsonic A90.

Phil Weldon

For resolution 1280 x 1024 my CRT monitor maxes out @ 85 Hz vertical refresh rate. Any higher refresh rate for this resolution and my monitor gives me a basically blank screen containing the message "signal out of range". I wait 15 seconds after that and the setting then returns to what it was previously. 1280 x 1024 @ 85 Hz used to work just fine for me, until I had to move out of my rented living accomodations, and into a house that I actually co-own together with my sister since several years back. Now, to answer your questions regarding trying the different settings, first a preamble: In case you hadn't followed the other thread I posted in this group, I need to explain: This house is located as close as any house can be legally built to a major (three tower wide) high-voltage powerline easement. In fact part of the easement spills right into my property. The

60 Hz AC current in these powerlines generates a weak, but significant oscillating magnetic field which is just strong enough to distort and disrupt CRT image performance that is not running at the same frequently of 60 Hz. That's is okay for viewing TV video (especially since one obviously cannot typically change one's TV refresh rate from its factory preset of 60 Hz, even if one wanted to), but is kind of bothersome for the up close viewing as when using a computer monitor. Thus I actually bought an LCD monitor to side step this PL interference problem entirely for my daily computer tasks. Anyway, back to the subject... In an effort to counter the PL interference, I've experimented by temporarily setting my monitor to (unacceptably) low resolution settings (e.g. 640 x 480) so as to be able to achieve and test much higher refresh rates. What I've discovered is that at refresh rates of around approx. 120 Hz and above, the interference on the screen diminishes to a level that is barely perceptible. While there is no CRT interference experienced at the 60 Hz setting, 60 Hz refresh rate is not acceptable for my main purpose here, in which, I'm aiming be able to view high-quality, high-resolution, stereo 3-D video --i.e. employing LCD shutter-glasses, etc. (My other purpose is to use this CRT along side my LCD as a second monitor providing for an extended Windows desktop.) High-quality, high-resolution, Stereo 3-D video will actually require refresh rates of something above 120 Hz (e.g. 130 to 144 Hz) at resolutions ranging from 1024 x 768 up to 1280 x 1024. However, the highest refresh rate I can achieve at a resolution that is the bare minimum acceptable for my purposes here (i.e. 1024 x 768) is only 100 Hz. (BTW, further to the above paragraph, 100 Hz provides some, although inadequate, improvement in noticeable interference compared to the 85 Hz setting.) Of course 100 Hz is far short of the > 120 Hz refresh rates I'm going to need here.

Now just to be clear here, I have in fact accepted the fact that in order to get the kind of "high refresh rate to high resolution" performance I'm after here I'm simply going to have to buy a good monitor that offers this capability. In other words, I'm no longer entertaining the "overclocking of my existing CRT monitor" idea. One monitor model I'm thinking at the moment of possibly getting is a "22" (20" viewable) iiyama HM204DT. It's video input bandwidth is 390 MHz. Displays 1280 x 1024 at 133 Hz... MSP: $699 USD. Hoping to find _equivalent_ (of at least as good, if not better, value) alternative CRT products/models so that I can at least do some comparison shopping here before taking the plunge. I'm open to product suggestions from anyone here in this vein...

Ken

PS: Someone, I forget who, suggested that my monitor "resolution to refresh rate" options were limited perhaps not by the monitor itself, but by, either, my adapter card or its default settings (which supposedly, I guess, might not occur to some people to change). This is not the case. I have explored all the valid settings that my adapter provides. And while it's hardly a very expensive adapter, according to its specs it is capable of displaying, for example 1024 x 768 @ 150 Hz. If the monitor could only keep up, such a setting would basically suffice. Of course, to find an adapter card capable of displaying the higher resolution of 1280 x 1024 at such a desired high refresh rate poses no concern to me in any way, as such high performance adapter cards are, both, quite affordable, as well as easy to shop for. Still, no use in buying one of these until I get a CRT monitor that is capable of taking advantage of the performance parameters which my choice of new adapter card will be intended to support.

TIA, Ken

"Phil Weldon" wrote in message news:rZM1g.6353$ snipped-for-privacy@newsread3.news.atl.earthlink.net...

'Ken Moiarty' wrote, in part: | For resolution 1280 x 1024 my CRT monitor maxes out @ 85 Hz vertical | refresh rate.

My Viewsonic A95f ALSO maxes out at 85 Hz for 1280 X1024. BUT, it will do

1280 X 720 @ 120 Hz. I suggested you try that resolution and vertical refresh rate with your Viewsonic A95 as a temporary workaround for 3D.

As for the effect of the high tension lines, without knowing what you see on your screen, if what you see is a faint rolling bar, I'd have to guess that it is not the magnetic field of the lines, but the interference induced in your house AC feed, or even in the house wiring.

Phil Weldon

Now that you mention stereo...

I have seen reference recently to a new LCD panel design allowing for viewing stereo directly by what seems to be an analog of the stereo photos that use a grid of cylindrical lenses in front of a still photo, where the left and right pictures are successive vertical stripes, and the grid of lenses directs the appropriate stripe's data to the 'right' eye.

I forget where I saw it or who was working on it; maybe Samsung.

The bottom line is that maybe this kind of display would have milder refresh requirements for stereo viewing.

The bad thing is I have no idea if this is already happening or still being developed.

Gino

PS. The LCD I mention doesn't use lenses, but physical barriers that prevent one eye from seeing the pixels intended for the other eye.

PPS. I was one of those who mentioned possible limits on the video card's capabilities. I admit that it was speculation on my pert - sort of trying to be a messenger of doom and gloom, I guess :-)

On 4/21/2006, Ken Moiarty posted this:

--
Gene E. Bloch (Gino)
letters617blochg3251
(replace the numbers by "at" and "dotcom")

Okay, I'm trying the 1280 x 720 @ 120 Hz as we speak. It works. I wasn't motivated to try it at first as 1280 x 720 resolution is video wide screen (16:9 aspect ratio) format and as far as I'm aware (at least at this stage in my pursuit of stereo 3-D video), most (if not all) high-resolution stereo

3-D video content available is from IMAX film productions which match the video standard (4:3 aspect ratio) screen format.

No, no... Nothing like that.

Well I've explained this to once skeptical others before you, times too numerous to recount. Let's just say here that if it can't be the oscillating magnetic field from the power lines -which, by the way, produces other interesting effects around the house, like bright blue 'star-like' arcing between the aluminum soffit panels which can be seen any evening after dark (a soffit grounding * issue I have yet to have repaired)- then the local city engineers who've seen to it that it be required by law that the aluminum gutters, the aluminum window frames, the sheet-steel central-heating ducts, and all other significant metallic surfaces of houses such as mine (i.e. those being right next to such major powerlines), * must have special grounding, don't know what they're doing. (Of course, I mean this remark tongue-in-cheek.)

• {Being that it is oscillating, not unlike that created mechanically by the rotating permanent-magnet containing armature of a generator, this magnetic field from the PL is capable of inducing currents in these close proximity metallic forms. These in turn can pose a fire hazard due to inevitable charge buildup and the arcing that results in the absence of effective special-purpose grounding to drain off this charge buildup. Now, while having described why how this is so, the induction of electrical current in metal surfaces is _not_ the same process that is responsible for the oscillating magnetic field's interference with my CRT monitor (which is actually due to its having a _direct_ influence on the CRT's electron-beam trajectory, which thereby adds to, or 'contaminates', the otherwise delicately synchronized and cleanly precise internal control of said beam's scanning of the phosphor screen), it illustrates just how actually significant the oscillating magnetic field originating from these powerlines in fact is, at this close range.}

Ken

Yes, I've read about this technology. Apparently it has been developed well enough (as of a while ago already) to produce LCD monitors capable of displaying full stereo 3-D video without requiring the wearing of shutter-glasses by the viewer(s). This is done with with the use of these cylindrical lenses as you describe, which are called if I recall, "lenticular lenses". Lenticular lenses, if I understand correctly, have been used with still images for many years now, for example, producing 3-D or "holographic" images as are common on credit cards, driver's licenses, Microsoft software security logos, etc...etc... You can actually buy software that will enable you to print images in such a way that when you accurately affix the associated special plastic lenticular lens sheet over top of the printed image, it will then appear in 3-D.) In the case of the

3-D LCD panels, as you describe, lenticular lenses are placed over corresponding alternating "left field" and "right field" LCD columns. If I recall the only major hurdle left to overcome has been figuring out how to market it to the masses so enough people will want to buy it in order that it can be manufactured on an economy of scale large enough such that it can be priced just right in order to generate the consumer demand for it to make it profitable... (A common catch-22 of marketing to consumers many a novel invention/technology, I would think.)

Ken

Lenticular screens produce a kind of 3d effect but it is different from a hologram. The images that are used as security features on credit cards are usually holograms--I'm not sure what Microsoft is using but the presence of shadows suggests lenticular.

Lenticular screens were around when I was a kid, before the laser had been invented. Holograms came along later--I made some as a senior physics project. In the art world the lines between them are not distinct, in the physics world they are very clear.

--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)

Think carefully before buying an Iiyama 22" CRT monitor. I've owned the A201HT and the HA202-DT and a colleague has a something-203-something. All three are somewhat blurry at

1600 x 1200 due to convergence problems. I was unable to correct this through the OSD.

Their 19" CRT monitors are OK. Their 22" CRT monitors look good on paper (good specs for the money) but your eyes might not like them.

hardware.fr recently tested three CRT monitors : the Philips

109B60 (19"), ViewSonic P227FB (21") and Iiyama MA203DT (22"). They found the same thing I did ; the Iiyama is blurry. They recommended the ViewSonic.

--
André Majorel 
"The best justice that money can buy."

No, not those 3d images those are real holograms produced using laser photography, and mass produced using a photographically etched stamp and a layer of metal, the images have a prismatic effect producing all the coulours of the rainbow dependant on viewing angle and lighting conditions..

the 3d images produced using the lenticular grating are fabricated using specially textured layer of plastic with a specially formatted image printed using ordinary ink on ordinary paper behind it. they are about 1mm thick. often the images are cartoon-like drawings and appear with real colours.

In the case of the

could a sheet be placed over the front of a regular LCD display. with 24-bit-per-pixel video each colour bar is individually addressible (in its own byte) which simplifies the software. it'd just be a matter of calibration, and apropriate drivers then.

I realise that if the lenticular sheet is integral it reduces those sort of hassles, but it seems to create a demand an entry level solution might work better.

Bye. Jasen

Thanks, John, for adding this clarification to the discussion.

I just looked at two MS installation CDs. Their top surfaces are quite clearly holograms. I don't seem to have any MS stickers on the boxes or anywhere else I can find them right now, so I can't comment about them. I recall that they are holograms, but can't verify that.

What I read about the stereo LCD monitors included diagrams showing that the videos for the two eyes were separated by opaque strip barriers, not controlled by cylindrical lenses.

BTW, Ken, "lenticular" just means "lens-shaped", although it could just as easily mean "bean shaped" :-), since "lens" comes directly from the Latin word for lentil. The term might have been "lenticular ridges" or some such... Someone said "lenticular grids" somewhere in this thread, I think. Sounds good to me.

Gino

Please forgive me if this is a second posting - the original (four hours ago) seems to have evaporated into cyberspace. -- Actually, my bad. I just learned something about Follow-up to :-)

alt.comp.hardware.overclocking,rec.video.desktop,sci.electronics.misc,sci.electronics.repair

--
Gene E. Bloch (Gino)
letters617blochg3251
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Gentlemen, This discussion was NEVER even remotely on-topic for the rec.video.desktop newsgroup (which is about television editing) And it has gone far afield from even the original inappropriate topic.

PLEASE remove rec.video.desktop from further postings. Keep Usenet usenet discussions in their appropriate newsgroups for everyone's benefit.

Thank you very much.