[dtvmcdonald]

Good grayscale???

Answer: CONSERVATISM and a dark room.

You need a dual probe scope that can subtract. I have a pile
of Tektronixs that do fine.

Attach probes to the CRT red grid and any CRT cathode (i.e. either side
of Sam's R284.) Scope in subtract mode so you measure the grid to cathode voltage.

Adjust for a good picture, not very bright, well below blooming or other "obvious"
problems. The image you are looking at needs lots of both full black and
full white, and preferably full red too.

When you turn up either contrast or brightness you will note double clipping of the red.
and thus compression.

The DC restorer clips one extreme and the CRT itself clips the other. Turn up
the contrast too much and they BOTH clip. You want to avoid this like the plague,
its bad for the CRT and makes the picture turn cyan.

So what I did was to make up little arrows out of red and blue masking tape.
I set the contrast and brightness at the middle of the "usual" range and attached
a blue arrow to both knobs, pointing up. I then turned up the contrast to just
below the double clipping point and attached a red arrow to it.
i returned the contrast to the blue arrow and turned the brightness to the double
clipping point and attached a red arrow to its knob.

So, when adjusting the set, if you DO set one knob above the red arrow, you
need to set the other one below the blue arrow by an appropriate amount.

I also added blue arrows to hue, color, and tone.


You could also attach the scope across R284 and set the arrows so you never
get (dc) current flow (you will of course get spikes at sharp edges.)

One other note: at constant line voltage, my settings for these have remained
correct for three years now! Never Twice the Same Color is simply wrong.