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Convergence, Geometry, and Mechanical Alignment

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Tip from Tom Herman:

1. Mechanically Aligning the TP61H95

Sunday, I did a full mechanical alignment, geometry setup, and service mode reconvergence of my TP61.

My original motivation was an irksome slight tilt of the image, noticeable to a critical viewer on letterboxed programs (right side about 3/16" lower).

I've corrected the overall tilt, and also have the added bonus of geometry errors, distortions, and curvatures reduced to an extremely low level (probably as low as you can get on a large analog display), as well as reduced overscan to preserve more of the original image.

I suspect the TP61 procedure here would be applicable to most other RPTV sets in the Toshiba line, but I make no guarantees.

Total time : about 2.5 - 3 hrs. Allow more time if you are unfamiliar with the basics of navigating around Service Mode.

Six months ago, I wouldn't have imagined undertaking a task like this. But after months of "osmosis", of all the collective wisdom & knowledge of the DT Forum membership - I felt ready to take it on!

The preferred start from scratch setup sequence described in the Toshiba manual, as you might do when replacing a CRT, is :

  1. RGB cutoff (using 'Screen VR' trimpots & Service Mode Settings) RGB focus (mechanical lens focus & 'Focus VR' trimpot). Opportunity to reverse lenses 180 degrees & remove the 'mirror' (aka Screen Protector)
  2. Picture centering, tilt, geometry, etc
  3. Service Mode Convergence
  4. White balance / color temperature (RGB, final setup of cut & drive)
  5. Finally (not in manual), setup Design Mode parameters with AVIA disc to set color decoder, contrast, etc perfect with all inputs

Touching #1 & #5 will mess up a lot of stuff related to Gray Scale & Color Temperature.

Setting focus (item #2) may subtly affect gray scale (see some Dean Roddey threads), so you might have to do a bit of gray scale adjusting anyway.

IMHO, instrument assisted is probably the best & most objective way to set gray scale/ color temperatrure, although good results have been reported by "eyeball" setup when done by experienced people.

What I describe below, is ONLY items #3 & #4. In the near future I plan to attempt Focus (#2). With better focus, flaws in convergence may be more apparent, so a convergence touchup may be needed.

Let's begin !

1.1. CAUTIONS

  • Not for the faint of heart. Your first reaction may be "Oh, no! What have I done to my $3000 set!". But the procedure is straightforward, if you have basic mechanical skills you will be fine.
  • NEVER change any Service Mode settings without first writing down your original settings.
  • You will be working near high voltages. Know where your hands are, don't grope. I bumped against one of the circuit boards & got quite a jolt. Don't drop any metallic objects or tools against circuitry.
  • Don't leave the opened up set unattended for even a moment, if there are children around. Children & exposed electric wiring do not mix.

1.2. MATERIALS NEEDED

  • Toshiba Service Manual
  • #2 phillips screwdriver (not mangetized)
  • 7mm socket, " drive universal joint, and " drive screwdriver handle are VERY handy for loosening & tightening the screw holding the yokes on the CRTs.   I recommend against a ratchet style handle; you need a light touch, it's easier to control the screwdriver handle.   While you could use a phillips screwdriver, use extreme caution to not press down hard while gripping the screw, to avoid damage to the CRT.
  • Masking tape (3M blue painter's tape), string, & tape measure. A 3-4 foot level is also nice to have.

1.3. Establish Screen Center

  • Verify cabinet is plumb & level using the 4 foot level.
  • Apply short strips of masking tape to the screen bezel, at the 12, 3, 6, and 9 o'clock positions.
  • Measure & mark on masking tape, the exact center of the screen dimensions. 
  • Stretch a tight string across the vertical & horizontal centerlines marked on the masking tape. Tape string securely in position.
  • Verify string centerlines are plumb & level using the 4 foot level.

Note, the horizontal string will slowly droop. Pull it tight just before any critical setups.

1.4. Enter Service Mode

  • Unplug all cables in the Video1 input, otherwise the built-in test patterns don't display.
  • Remove the front speaker grille (held in by Velcro).
  • Remove the plastic cover behind the grille. The 3 CRTs and various circuit boards will be visible.
  • SVM Disable (with power off) - now is a convenient time to disable SVM, by unplugging the yellow/white pair of wires going to the small circuit board mounted on each CRT. While SVM can be disabled in Design Mode, I chose to positively, physically disable it. Tag each of the 3 pairs with tape, as a future reminder that the wires are intentionally unplugged.
  • Warm up set at least 30 minutes.

To enter Service Mode,

  • Press & release 'mute' on the remote
  • Press & hold down 'mute' on the remote
  • Behind the flip down door , press & release 'Menu' button. Release 'mute' button. An "S" will appear in upper right screen.
  • Press & release 'Menu' button again.
    You're now able to see & adjust Service Mode items. 'RCUT' and its value will be in upper left screen.
  • Pressing 'Channel Up/ Down' on Remote scrolls thru the various items.

'Volume 'Up/Down' changes the numeric value of the item. NEVER change any Service Mode values without first writing down the original setting.

Pressing 'TV/Video' on Remote scrolls thru several built-in test patterns. Patterns don't display unless all cables are unplugged from the Video1 input.

Advance to the 'White Cross on Black Background' test pattern.

1.5. Prepare for CRT Yoke Alignment

The general idea is that software settings in Service Mode will be set to a nominal value, then mechanical adjusting is done, and finally Service Mode software settings are used for fine tuning & touchup.

Green is the reference color, to which everything else will be adjusted relative to, probably because Green is the easiest to see accurately. 

Take your time to get the Green adjustments set especially accurate.

CAUTION: don't grope & accidentally touch a circuit board.

From left to right, are the Red, Green, & Blue CRTs.

Did I remember to say "NEVER change Service Mode values without writing down the original setting?"

  • Set Service Mode HPOS = 4B, VPOS = 0B.

On the CRTs yoke assembly, are 2 small, rotatable plates. There is a tab on each plate for grasping. Rotating the plates (each is separate) moves the Cross in X-Y (left/right , up/down).   It does not affect image tilt.

  • With 7mm socket, loosen the screws clamping the yoke on each of the CRTs.

Rotating the whole yoke, affects the tilt of the Cross, but not the X-Y position of the Cross.

For TW40x81 sets:  "The top clamp is the one that should be loosened for the tilt adjustment. Use a non-magnetized screwdriver so you don't accidentally "degrade basic function and result in no variable quantity" as the service
manual puts it." (Tip from Stephen Smith)

1.6. Set Image Tilt & Centering

  • Verify the stringlines are level, taut, and haven't shifted.
  • Rotate the plates/ tabs on yoke, to move the Red & Blue images well away from the Green. You want to be able to see the Green Cross without any overlap of the red & blue.
  • Start with the Green CRT.
    Rotate the Green yoke to get the Green Cross level to the stringline, without tilt.   Tighten screw on yoke. Do this as accurately as possible.   This is the ONLY adjustment for image tilt.    Tightening the screw maddingly shifts the image, so you may have to "overcompensate" Tilt and have the screw tightening bring it back to perfect.
  • Rotate the 2 plate/ tabs on Green yoke assembly to move the Green Cross in X-Y (left/right , up/down). Get the Green Cross centered on the stringline.
  • Unlike tilt, fine tuning of the Cross center is possible in Service Mode settings, so it's not necessary to go bonkers trying to get the XY position of the Green "perfect".
  • If necessary, touch up Green Cross Tilt again, then X-Y center again.
  • Adjust the yoke on the red CRT to match Red Cross Tilt & X-Y position to the Green Cross, as accurately as possible. Tighten the yoke screw.
  • Adjust & tighten yoke of Blue CRT to match the Blue Cross Tilt & X-Y position to the Red & Green Crosses, as accurately as possible.
  • Do a final check for overall Tilt & X-Y centering of the white Cross. It's more important to get the average Tilt right.
  • Convergence of the central part of the Cross should look pretty good.   Don't be too surprised if there are noticeable convergence errors on the ends of the cross, or if the Cross arms have a slight curvature. This will get adjusted later.
  • Now use HPOS & VPOS in Service Mode to do any final touchups of the White Cross center, to the taut stringlines. It shouldn't need much if the mechanical setup was done accurate.

1.7. Set Picture Height & Width

Basically fine tuning the amount of image overscan.

  • Service Mode HIT = height, WID = width.
    Reduce HIT until the white ends of Cross are visible and clearly "too short".   Advance HIT until white ends just touch edge of screen.
  • The Toshiba manual says to advance HIT another 8 steps. This sounds like way too much overscsan. I advanced HIT 3 steps, final HIT value 43.
  • Do the same for for WID. After the White Cross just touches the edge of the screen, Toshiba says to advance another 12 steps.   I advanced it only 3 steps, final WID value 26.
  • Press 'TV/Video' on Remote to scroll thru the other test patterns. Confirm the HIT & WID overscan is the least amount necessary to cover the screen, without static or junk in the extreme edges.
  • You may notice that red, green , and blue overscan may not be perfectly symmetrical. On my set , even though Cross Center was perfect, the ends of the red cross was further left than others, and end of the blue cross was furthest right. I'm not sure why. Maybe it's because the convergence was off in the extremities, and convergence is not done till later.

1.8. Set Overall Geometry

Service Mode parameters VLIN, PARA, CNR, & TRAP are used to set overall geometry for straightest possible, undistorted lines.

  • Press 'TV/Video' on Remote to scroll to a built-in Grid test pattern. Need full Grid, not just a Cross.
    • VLIN - adjusts the grid spacing in the vertical direction to be all equal. My original VLIN setting was good.
    • PARA - adjusts the bow in / bow out of the vertical lines, near the edges of screen. Adjust for straightest lines.
    • CNR - adjusts bowing/ curving of vertical lines, near the screen corners. Adjust for straightest lines.
    • TRAP - adjusts the vertical lines in a trapezoid fashion. Adjust for straightest lines.
  • Repeat VLIN, PARA, CNR, TRAP until grid lines are overall straightest.
  • Any remaining bowing & distortion of grid lines should be very slight, and will be corrected in Service Convergence.
  • Press 'TV/Video' on Remote to scroll to the all white test pattern.

1.9. Service Convergence

The main purpose is to get RGB perfectly converged over the 55 - 60 points of the Convergence Grid.

Unlike User Convergence, which allows XY adjustment of only Red & Blue relative to a fixed Green,   Service Convergence allows adjustment of all 3 CRTs including the Green.

The Green is adjusted by itself , first, with the Red & Blue turned off . To "what reference " is the Green adjusted ? Green is adjusted to fine tune any small remaining bow, distortion, and geometry errors that remain.   I set it by eye, although one could set more stringlines across the screen to be certain.

After Green is adjusted for minimum geometry errors, Red & Blue are converged to the green. If my set was better focussed (I skipped the mechanical & electrical focus), the Convergence could have been set more precisely. When I do focussing later on, probably Convergence will need touch up.

With all Convergence adjustments, start near the center & work outward. There is interaction, you'll have to repeat the 'center & outward' several times, so don't spend too much time on the first iteration.

To begin,

  • From within Service Mode, press '7' to enter Service Convergence grid.
  • Buttons 100, 0, and ENT turn the Red-Green-Blue CRT , on/ off.
  • The color of the flashing box cursor, is the CRT that is being adjusted.   Pressing '3' switches the cursor color & CRT.
  • With a flashing cursor, press 2 (up), 8 (down), 4 (left), or 6 (right), to move the flashing cursor around the grid.
  • Pressing '5' changes cursor from flashing to solid, to do an actual adjustment.   Now, pressing up/down/left/right actually moves the grid color corresponding to the cursor color.
  • Start with the Green only grid, adjust it for best possible geometry. DON'T TOUCH the Green after this.
  • Next, converge the Red relative to Green (Blue off).
  • Next , the Blue. Blue is hardest to see accurately. Ideally the Blue should also be set to the Green, but I found the lack of contrast too difficult, so I converged Blue to Red (with Green off).
  • Finally, turn on all 3 CRTs.    Do final touchups of the Red & Blue convergence relative to Green, but DON'T touch the Green.
  • When finished, press '7' to "freeze" the new Convergence settings. The Grid will momentarily "implode".   Press '7' again to exit the Convergence Grid, back into Service Mode. Turn the set's power off/ on to exit Service Mode.   

1.10. Finally,

  • Re-install all panels & grilles.

You can end here, or proceed to an AVIA / VE setup. Using previous postings from Cheezmo, Mike Suave, Dean Roddey, and others, you can also fine tune all Video inputs for best color decoding, etc.

According to the AVIA disc, the necessary amount of overscan can depend on whether the picture is mostly dark or mostly light. It's influenced by the set's power supply design.

AVIA has both 'white on black' & 'black on white' Overscan Test patterns.

The Toshiba seems to do essentially identical on both.

I ended up with about 2-3% overscan in the vertical (Y), and about 3-4% horizontally (X). The overscan was symmetrical in both X & Y.

Enjoy your near perfect geometry !