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Astigmatism Adjustment

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Tip from Stephen Smith"OK, here goes. Ignore the service manual instructions (Toshiba). And the set's internal test patterns don't help much because they're such low quality. Do this:

  1. Put the set in Normal mode (for max 100% contrast) and Full TW mode
  2. set STC1-STC6 to 80 in designer menu.
  3. display the AVIA 100 IRE Dots pattern.
  4. use the TEST param to enable only one gun at a time (values 85, 86, 87) and for each:
  5. adjust the centering magnets to center the raster on the screen. I do use the internal white cross test pattern for this.
  6. rotate the focus VR to the right and adjust the 2-pole magnet to make the dots as circular as possible. Use the dots in the center of the screen, because the edges will always more oval due to the angle of the CRT
  7. rotate the focus VR to the left about 3/4 all the way. With AVIA's dot at max contrast you can actually see a darker blob inside a halo. Adjust the 4-pole magnet to make as much equal halo around the center. That's the coarse adjustment, but now you want to adjust the 4-pole so that there is *minimal movement* in the dots as you rotate the focus VR from one extreme to the other. This is a little tedious since you're trying to adjust and evaluate with both hands at the same time.
  8. again adjust the centering magnets to center the raster on the screen.
  9. Repeat for each CRT.
  10. Set TEST back to 84 to enable all guns and fine tune the centering magnets to get the center of the screen as converged as possible.
  11. hot glue the tabs so they stay in place.
  12. (optionally) correct geometry using TW overlay grids.
  13. Service converge all modes.
  14. Double-check image center using AVIA and adjust VPOS/HPOS if necessary.


  • Ignore the 6-pole magnet rings. They have no purpose or affect (confirmed by Toshiba).
  • Make sure to be in Full mode and use the Dots in the Widescreen Enhanced menu (so that no TW stretching is altering the shape of the dots).
  • if you only have VE, then use TW2 for it's Dots pattern

If things still don't look right, your can try these designer params and repeat the above. It probably won't help unless your STH's are not 7B (mine was left at the EEPROM default of 77):

    STRH, 1STH, 2STH, 3STH: 7B
    STRP, 1STP, 2STP, 3STP: 95
    VLD, 1VLD, 2VLD, 3VLD: 44, 44, 4B, 4C

To see exactly what these params do:

  1. display the Full mode service grid with green lines only
  2. exit back to service menu but leave the grid displayed (ie. press 7 just once)
  3. enter designer menu and adjust STRP (horizontal), VLD (vertical), and finally STRH (lateral?). STRH is where you can probably fix uneven line widths on the sides.
  4. repeat for TW1, TW2, and TW3. You can see the pattern in the param names


PS. Here is a blurb from the Toshiba product brochure (and web site):

A picture tube (or CRT) has an electron gun that sends the electron beam to the faceplate of the tube to make a picture. The distance from the gun to the center of the tube is different from the distance to the edges and corners of the tube. In addition, the angle of the beam is different, causing an elliptical instead of round beam spot. Because of this, edge and corner focusing usually suffers. Dynamic Quadruple Focus adjusts the speed and angle of the electron beam so that it produces a fine round beam spot everywhere on the tube. This ensures a sharp clear picture from corner to corner.

Well I can't find any evidence of truth to that on my set. Spot size is grows more oval as the distance from the CRT to the screen increases. But I'm not losing any sleep over it, though.

Tip from Mr Bob:

Here is Mr Bob's comments to Stephen's input.

"And y'all now have a very specific and erudite description of how to do the astigmatism realignment on a CRT. The only change I would make would be to point out that sometimes turning both the magnets in a pair TOGETHER causes the change you want to make, as opposed to turning them opposed to each other, which always makes a much more drastic change.

And that turning the focus VR for a particular color takes it OUT of focus in that direction, and then OUT of focus in the other direction, going the other way, skipping the midpoint, where it IS in focus. The astigmatism realignment is done exclusively with the CRT OUT OF FOCUS electrostatically, both CW and CCW at the focus knob. Then it gets brought back into focus to check out and see that the horizontal and vertical lines in the crosshair stay identically thin when you're in absolute crispest focus.

When the vertical is still out of focus while the horizontal is in, or vice versa, you know you still have work to do.

AND I wouldn't try towing these magnets off of their factory settings by too much at first--just a quarter-inch of turn at a time until you know what you're doing.

AND I would mark them very carefully, with as thin a line as possible from your Sharpie, before breaking the factory seal at all, to make the adjustments. You may need those settings back, if you totally destroy the astigmatism alignment.

AND don't ever get the centering magnets mixed up with the astig. magnets. The centering mags are always closest to the CRT face, and the astig. magnets are always closest to the ECB socket.

The only exception to this is with the old Kloss reverse, curved mirror refraction-type CRTs, where it is the opposite.


There are one or two exceptions to that rule, such as the 64 point convergence and the focus VRs, but it is a VERY good general rule to follow.


Or your next call will be to an ISF grade tech, possibly necessary to import, to straighten out and realign your grayscale.

Be advised that you are taking your life in your hands--or at least the life of your TV--every time you embark on this grade of calibration, at this level. Just last week I had to charge a guy on the other side of the country a $75 consultation fee to straighten out what had happened when he simply got the focus and screen VRs mixed up. And yes, it took the entire hour, in 2 separate sessions, to get it all back on track.

He was overjoyed that I could save his bacon for only $75, but if he had actually looked at his instrument--the focus block--instead of ONLY at the manual, that expense would never have been necessary.

You can turn your focus VRs a lot, and the final optimum point is obvious on red and green, with the blue being more demanding but still fairly simple to do if you know what you're doing around how it affects the blue outlining vs. the grayscale.

The screen VRs, on the other hand, are a completely different story. They're intensely interactive, sometimes servo-controlled in other parts of the circuitry and menus, and very finicky, as just a TINY amount of turning can be WAY too effective on the screen controls."

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