Quote:
Originally Posted by mhennessy
That is how beam limiting is done in the vast majority of sets that I've encountered. Only a small number of those had the dag grounded directly. The way it works is really simple: the dag (and negative end of the EHT generator) goes to chassis via a resistor. There is 25kV nominally between dag and EHT. Beam current - via the cathodes - passes from EHT through to chassis. Hence, beam current passes through the resistor that connects dag to chassis.
Mark
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Hi Mark, thanks,
That , makes sense if the negative of the EHT generator is connected to the external dag, then through the resistor to ground the beam current could be sensed there. I have never owned a set that did this, the only ones I have seen have the external dag grounded, but mostly the ones I worked on were early models from the 1970's and early 80's.Though they might have has current sense resistors in the EHT negative.
Also, I guess for the CRT types where there is a resistive connection between the internal dag and the gun electrode structures, the stored bulb charge should self dissipate as there is a complete discharge pathway with the power off.
PS: What is a typical value current sense resistor for the application, also are they a physically large part ?