The video processor board is the one with RGB/YPbPr/Ext. sync inputs on it, and it actually does a lot more than just accept that input. All other input boards - NTSC, SDI, HD-SDI, and even the test patterns generated by the MPU board - pass their video through this video processor board. Its the job of it to apply brightness/contrast/gain/bias etc., and output the results to the RGB amp.
What might surprise you is that internally, everything is processed in YPbPr. The other input boards put their signals onto a single YPbPr bus, and even analogue RGB input gets converted to YPbPr for processing. It's only at the end of the chain that things get converted to RGB.
The video processor board contains many, many potentiometers that are there to calibrate the RGB->YPbPr->RGB conversions, and this is where we run into an issue: Three out of three video processor boards that I have tested are not properly calibrated and screw up the conversions in some way. What I would like you to do is test yours to see if it's the same.
The procedure is very simple. First, bring up the Color Bars screen in the 240p test suite:
Next, simply press the buttons on the front of your monitor that let you activate red-only, blue-only, and green-only. For example, blue-only should look like this:
There are two key things to look for here:
1. Red and green are completely absent
2. Blue and white (or rather, the blue component of white) are at equal intensity.
Please do this for red, green, and blue each.
If your video processor board is somehow not properly calibrated for the RGB<->YPbPr conversions, you might see other color bars showing up where they shouldn't (albeit only in whatever color is active) or you might see that the current color is not in balance with white.
One fellow I know who has two HTMs recently took some nice photos, and his monitors seem to have passed the test (still confirming about the one on the right, where there is some difference in the darker end of the spectrum). But with three of mine being out of calibration, it seems like this might be a common issue. Ikegami HTM owners, for your sake as well as others, it would be great if you could test this.
Thank you.
