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Color Decoder Adjustment

Although info below is for a Toshiba set, info could very well apply to other brand sets as well.

Some may be tempted to adjust values for RCUT and RDRV in an attempt to make all three colors zero on the color decoder check in service mode.  (Tip applies to Toshibas)

Tom Herman strongly cautions against this.

"NO! don't touch RCUT & RDRV, those affect the gray scale & color temperature. Whereas it may seem that RCUT, RDRV are affecting the color saturation, what they are really doing is affecting the B&W luminance portion of signal. Touching them could impart an overall color tint, even to Black&White. 

For bedtime reading on differences between a gray scale adjust & color-tint adjust, see this link.

The Toshibas have Design Mode parameters that affect the red & green decoder, so that you can separately & optimally adjust them in addition to the blue bars. 

To do the adjustments you need to be comfortable & fluent working in Design & Service Mode. Also need the AVIA test disc.

Do NOT touch any codes without writing them down first !

The relevant codes are as follows. Most people set Color & Tint thru User controls, but by setting Color & Tint thru the codes COLC & TNTC in Design mode, then Theater Preference defaults to the values set in COLC & TNTC. 

COLC (Sub Color Center NTSC)
TNTC (Sub Tint Center) (when in TNTC, the screen color balance goes screwy, you have to leave TNTC to actually be able to check the result of the adjustment )

The procedure is :

First, set Color & Tint using AVIA flashing blue bars with blue tinted filter over your eyes, in the usual way. You may use either User controls or Design Mode COLC, TNTC.

Next , adjust the AVIA flashing green bar pattern. Hold the green filter over your eyes. Like the standard blue bar, adjust so that the green flashing appearance thru the filter is minimized. Adjust the ECLP parameter. Bit 1 increase green saturation slightly. Bit 2 increase green saturation more.

Call up the AVIA flashing red bar , use with the red filter over eyes. There are two parameters that affect red, ECLP and ECLT.

Bit 3 increase red saturation.
Bit 4 increase red saturation a lot & affect magenta.
Bit 5 increase red saturation.
Bit 6 increase red saturation & affect yellow.

Bit 2 lowers red saturation
Bit 3 lowers red saturation more

Go back & re-check flashing blue, green, & red bars, adjust one more time if needed, since they interact.

Your overall color decoder accuracy should be +/- 5% or so after doing this.


Here is Stephen Smith's input:

I did the service menu adjustments to the color decoder params for both Theater Video and Theater DVD (component).

I found it much easier to use the ETES param plus the green-only and red-only AVIA color bars rather than the filters and color decoder pattern. The X81 series includes a new ERGB parameter, which you should also include in the adjustments.

Start with the ETES set for green gun only and the green-only color bars. Adjust ERGB for best green match, giving preference to the hue bars. Then adjust ECLP: Buttons 1 and 2 on the remote affect green, while the rest affect red. See if you can get a better green match. Then change ETES to red and fine tune ECLP and ECLT for best red match.

Also, ERGB, ECLP and ECLT only affect video inputs (s-video and composite). You have to do this same procedure for the other input modes:

Component 480i Theater DVD: EHNR, EHNC, ECLT
Component 480i Theater DTV: DERG, DECP, DECT

If you have a progressive DVD player or HDTV then you use those param sets.