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