== CRT triode characteristics == 

 Ok I think I'm ready for the next questions! I'm working on a color calibration guide for the sony trinitron line of CRTs using the service adjustment mode. It involves a piece of software called WinDAS (the DAS stands for digital alignment system), and a special cable that connects a pc/laptop to the service port of the monitor. The WinDAS software instructs you to load up certain test patterns, and then allows you to adjust sliders until various luminance and chromaticity targets (as read with a colorimeter or spectroradiometer) are met . Early on in the procedure, you are asked to load a grayscale pattern, and adjust the G2 voltage until the second bar is barely visible against the pedestal bar. I think I have a pretty good understanding of G2 voltage, and its relationship to the G1 cutoff voltage, thanks to Kenneth Compton's text. From what I understand, the G2 voltage is the first real accelerator in the system: due to its positive charge, the electrons experience a pulling force along the tube in the direction of the viewscreen. The G1 grid, which is negatively charged relative to the cathode, acts as a valve of sorts. Lowering the (+ve) G2 voltage means that the (-ve) G1 voltage doesn't need to be as low in order to prevent electrons from being accelerated through the tube. In other words, lowering G2 means the cutoff voltage at G1 doesn't need to be as low, which means cathode loading is reduced (too low a cutoff voltage means that electrons are pulled from a smaller area of the cathode). However, I'm not as confident in my understanding of some of the following steps in the calibration procedure, and their relationship with each other. Right after the G2 adjustment, you are asked to keep the grayscale pattern on the screen, and adjust "G_Bkg_Brt_Cent" until the second bar is barely visible against the pedestal bar. During this part of the procedure, the screen has a green cast. I think the register stands for green blanking brightness Center, and I think the purpose of this step may be to set the voltage necessary for blanking the green gun when brightness is in the center of its range. Perhaps this is something like a Cutoff voltage for the green gun? Later, you are asked to make adjustments for Cutoff Max (with a black pattern), Cutoff Min (with 30 IRE), Drive (100 IRE), etc., but you're never asked to adjust the B_Bkg_Brt_Cent or R_Bkg_Brt_Cent in the same way as the Green one. You do adjust the B_Bkg_B_Cent and the red one during the Cutoff Min adjustment, but here you are just setting a chromaticity target with a 30 IRE pattern. I'm guessing the reason that only the green version of this register is done using the grayscale pattern has something to do with the fact that changes in "green" wavelengths have the largest effect on luminance.  

 So the questions: 

 1) Am I on the right track with these interpetations of the registers? 

 2) Everything I've read indicates that setting the G2 voltage too high is what is "unhealthy" for the tube. The only side effect of setting it low enough for really deep blacks is that the resulting gamma of the display is very high (image is crushed). However, this is easily remedied with a LUT adjustment after the WinDAS procedure. Are there any other considerations when setting the G2 voltage? Should I be worried about setting it too low? 

 3) I've heard that you can influence the gamma of the display by choosing different luminance targets at the different stages of the procedure (instead of the one WinDAS instructs. Do you have any guidance about tube health considerations here? Clearly, I want to keep peak luminance below 100 cd/m2 - my peak luminance ends up around 85-90 cd/m2 after the procedure. But what about during the Cutoff Max (0IRE) and Contrast_Min (30 IRE) adjustments. I'm willing to experiment with different luminance targets to see how it affects the gamma, but it would be nice to know that I can adjust these within a moderate range without risking tube health. 

 I recognize that these questions may be completely idiosyncratic to Sony's way of doing things, and that it's asking a lot, but I don't have anywhere else to turn to for answers at this moment, and a number of people including myself have been trying to figure this out for a while now. If you're unable to engage me here, for whatever reason, absolutely no offense taken - you've already given a great deal of time and energy here.