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Herman-TLV Maneuver Version 1
(Original Procedure)

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Below is the original procedure for Herman–TLV Maneuver from, Michael TLV, one of the authors who devised this procedure.

Michael, however, has discovered a better way to do this.  You can now further flatten the grayscale response curve to closely follow the D6500K standard. 

>>>  Click here to learn more about H-TLV Version 2.   <<<

A Step By Step Walk Through
(Original Procedure)

Warnings: You can do major damage to your TV’s existing grayscale if you try this. You may even damage your TV if you are careless in the implementation. The moment you touch the screen trimpots, there is no going back, you cannot undo the changes that you make. I take no responsibility for your actions or stupidity. The procedure is presented for entertainment purposes only.

Additional Warnings: This procedure has only been tested on Toshiba HD RPTV’s. Theory says that it will work on other types of TV’s, but this has never been confirmed. It may not work on the Sony sets … as per a note from Robert Jones about this. It may work on the Pioneer sets, but only to a more limited degree. I don’t know about Mitsubishi sets, but I suspect it will work there too to a limited degree. If you find that the screen controls are glued down … stop immediately.

Advantages as a result of performing this tweak include significantly improved focus and sharpness. Increases the ability of the TV to display fine details by 20% to 50% depending on how one does the math.

Before I begin, I have to say that I assume a certain competency on the part of the user as well as a willingness to sacrifice. And remember, I may not have included everything, but most of it is here.

  1. Get access to the screen control / focus control block on the TV. Note which controls do what. Read the label.
  2. Using either AVIA or Video Essentials, bring up the Pluge frame. (The one with the 4 or 5 gray boxes of varying intensities used for adjusting the brightness a.k.a. black level of the TV.) Keep this in the background.
  3. Enter the service menu and bring up the service convergence grid.
  4. Measure the vertical width of the center line on the grid. These are the lines running from top to bottom, not left to right. You should measure in the range of 10 to 11 mm, but this will depend on the TV. Larger sets will have thicker lines and smaller sets will have narrower lines. We will use the 10 mm measure as a guide and a reference point. Do the red grid first, then the green, then the blue.
  5. The procedure begins now. (You need a metric ruler)
  6. Do the Red CRT first. Shut off the blue and green CRTs. Turn the screen control to reduce the intensity of the red CRT. If you turn it too far, the grid vanishes. Turn it too high and you see the raster lines. From the 10 mm point, reduce the intensity until the grid line measures 7 to 8 mm. Shoot for 8 mm. It’s a guessing game so you will have to eyeball it.
  7. Do the Green CRT next. Shut off the red and turn on the green CRT. Reduce line thickness to 8 mm.
  8. Do the Blue CRT last. Shut off the green and turn on the blue CRT. Reduce the thickness to 8 mm. You will note that this may not work well and you may only be able to take it to 9 mm and not much more, but try for 8 mm for now.
  9. Turn on the other two CRTs. Turn red and green CRTs on now. Image is too dark, which is as it should be.
  10. Get out of the convergence mode by saving and clearing the grid from the screen. You can see the pluge frame again although very dark.
  11. Go to the BRTC parameter in the service menu. Increase the brightness until the pluge looks correct in terms of black level. The colours appear all screwed up … don’t worry about that yet.
  12. Now is the first check point. If the BRTC cannot restore sufficient brightness to the image, then you have turned down the CRT’s too far. Go back and bring up grid again and look only at the blue CRT. Shut off the red and green CRTs. Now Increase the width of the blue line marginally. Take it up to 9 mm. Turn on the red and green and save the change and return to the pluge pattern.
  13. The BRTC should now be too high so you can turn it down a bit. The image will also likely appear too blue.
  14. Now go to the RGB CUTS and RGB DRV controls in the service menu. Look at the bottom of the 4 or 5 gray bars and adjust the CUTS until the bars look gray to you. Not red gray or green gray or blue gray, but Gray Gray. Devoid of colour. Obviously a blue gray means to reduce the blue cut or increase the green and red cuts.
  15. When you get the dark end okay, then try the bright end with the white box at the top. Adjust the RGB DRV controls to get a white white and not a red white or blue white or green white.
  16. This eyeballing of the grayscale takes the longest time. When you think you have it right … to your "eye," change the material and bring up a fleshtone image from … say … Pleasantville or Fifth Element. Make final adjustments in either the CUTS or the DRVS.
  17. This is it. You are done. Procedure completed.
  18. Now you need to bring in an ISF certified person to calibrate the grayscale properly using a colour analyzer.

Read the background info on this procedure.

Excerpts from a thread on this technique (Dec 00)

Words of Caution from Guy Kuo

(Original Post)
I've chosen this forum with its advanced RPTV community to air concerns I have regarding this technique. I will not post this elsewhere, and once done here, I shall consider my obligation to the online community fulfilled. What happens to this is up to you in the community.

Lately, I've found multiple threads with DIY tweakers deciding to undertake this maneuver. I think it can be done in a responsible manner like Michael performs, but in threads on multiple forums there is never any good discussion of they underlying mechanism nor of the inherent risk of overdoing this. The cathode wear risk is insidious and problems would not be immediately noticable. An uninformed tweaker could potentially be losing years of the set's life without realizing what he has done. This may not actually shorten cathode life, but there has to be some form of informed consent and disclosure. I don't see that happening in the multiple enthusiastic threads on various forums.

Nobody has done a thorough, objective measurement of cathode deterioration efects with and without this maneuver. By this, I mean a CONTROLLED trial taking several displays, with varying degrees of and one without this change, all adjusted for identical light output and exposed to identical video signals for 3,000 to 5,000 hours of operation. The light output and image sharpness of the sets would then need to be compared. Without such a controlled comparison, nobody can definitively state the long term effect of the maneuver. This hasn't been done and is unlikely to be performed by anyone so the tweaker undertaking this maneuver MUST be informed that there simply isn't complete data yet. We do have sets in the field with several thousand hour times and Toshiba is apparently starting to do this, but this is NOT the same as data from a good controlled trial. We still cannot definitively predict its effects on CRT lifespan.

Mind you. I am no saying that cathode wear will be worse. It is likely unchanged with Michael's judicious technique. Problem is we just don't definitively know and the possible increased cathode wear may occur at a rate slow enough to be apparent only years after excessive adjustment. This is troubling because that means evidence of trouble would not even be showing up yet. I strongly feel this needs to be disclosed and discussed in the forum threads. I don't care if people dismiss these concerns, but they must hear about them before deciding to go ahead with the maneuver on their own.

The mechanism by which this works needs to be disclosed, particularly in the absence of definitive data on its cathode lifespan effect. This gives the owner or tweaker at least a hope of understanding why there is risk and some ability to weigh for themselves the import of limiting the amount of adjustment and final light output. The maneuver sharpens the image by forcing the beam emission to come from a smaller area of the cathode tip. This means that active portion of the tip must bear the load of all the beam emission. The greater the beam density, the faster that portion of the cathode will wear. One may be able to control that wear rate by reducing total light output. However, the amount by which one must reduce light output to keep the tip wear constant is not yet known because it has not been measured. Without a measured wear rate, we don't know if even cutting the light output to 1/2 or 1/4 of the already reduced ISF setting is enough to keep the tip beam density constant. The fact that we don't really know means we are guessing. The owner MUST be told that this is only an educated guess in order to make an informed consent.

Personally, I think this technique has good usefulness and thank Tom and Michael for sharing it. However, my concern is not over its technical merit but whether online tweakers get all the facts and know the extent to which risks are indeterminant. I feel there should be a moral obligation to the online HT community when DIY tweakers are told about a new maneuver with potental display lifespan ramifications. I'm sure Michael tells his clients so they know and understand, but what about all those reading DIY threads on the forums?

Should these concerns be added to Keohi's site since that is where many people will be learning how to do this? I won't ask, as this is ultimately Tom and Michael's technique, but I feel obligated to bring up these issues.

(Follow up Post)
This is not about the phosphor at the front of the tube but is about the cathode at the neck end of the CRT. The cathode is an CRT element which is heated to generate the electron beam. That electron beam is accelerated under high voltage to strike the phosphor at the front of the CRT and produce light. The electron beam is focused and controlled by various grids and beam lenses within the tube neck. The balance of electrical forces in the grids control the beam and to some extent what portion of the cathode emits electrons. The very tip of the cathode is easiest to have emit electrons. As that area is worn the more peripheral areas come into play. Thus, we see CRT's naturally blurring as their cathode reaches the end of its life.

The electron beam spot which strikes the phosphor face is for our intents an image of the active tip of the cathode. The HTLV maneuver changes the charges at the screen grid (G2) and coaxes the cathode to emit more of the beam from just its tip. Since this is a smaller area, the beam spot size becomes smaller and the resulting picture gets sharper. This is not the same as adjusting the beam focus because the active cathode area is being altered, now how well it is focused by the beam lens.

The concern is that doing so excessively could accelerate the natural wear which occurs at the cathode tip. As the tip ages, we see more and more of the periphery being forced to emit electrons and the spot grows larger. If G2 is forced too low (darker), the cathode can wear out unevenly and prematurely lose its ability to emit electrons from the center of the tip. One would see an initially sharper image, but later be dismayed to find the tip completely inactivated and only the cathode periphery active. Once that happens, it would be impossible to achieve fine spot focus. All CRT's blur over time, but if misapplied this technique has the potential for making that happen more quickly.

Michael, as a professional, judiciously limits the amount that he applies this maneuver. I just don't want to see over enthusiastic DIY tweakers unwittingly overdo it in newfound excitement over making things sharper. A reasonable amount is probably good. Too much could be very bad but not immediately noticeable. From there comes my lunatic seeming caution.

Tom Herman's response

Excellent post, Guy. This should be a required reading for anyone contemplating the HTLV tweak.

In some of the forums I get the uneasy feeling that people haven't absorbed & understood the non-zero risks.

My educated guess is, that as long as the width of vertical grid lines is reduced from 10 mm to no less than 8mm, then we're within Toshiba's margin of uncertainty on CRT setup.

I say this because of my initial experience about a year ago on my TP61H95 set. I very literally followed Tosh's service manual on setting 'Screen VR', so that the CRT "raster" was just barely at the onset of visibility. After getting a professional gray scale, I ended up with about 8mm line width. Of course, I have no data re CRT longevity, so this is an "educated guess". Michael Chen has greatly refined and popularized the tweak during the last year.

Michael TLV's response


I estimate that my set has been in operation for atleast 2500 hours since implementing the technique. For now, I have not noticed any change in performance. Periodic checks with the VE disc indicate that everything continues to operate within acceptable parameters.

On an aside, I had a big Lens Striping challenge on the weekend and the final result was very different from the procedure previously discussed. There were strips of tape on both sides of the red crt and on the outside of the blue crt.

Michael @ The Laser Video Experience

Keohi HDTV responds

Hi Guy and Tom,

Actually Guy's concern applies not only to this technique but to most, if not all, of the info at my site and other tweaker sites.

Reading about it is one thing. Doing it with some experience and wisdom is another.

Will add your comments as a precaution to those who are thinking about implementing it.