I was looking at these schematics and noticed something curious.
Can someone elaborate on the functions of the green bracketed area and how do they work?
Schematics include Newcomb KX25 and KX50 mixer amps. Only amp sections are shown.
Can someone elaborate on the functions of the green bracketed area and how do they work?
Schematics include Newcomb KX25 and KX50 mixer amps. Only amp sections are shown.
I can, but maybe not before someone else does. There's an indicator tube that is setup to show when the amplifier is being overloaded by the input signal and volume control settings. The circuitry you've outlined supports that indicator and includes the indicator tube itself, the 6AF6. It has two independent "shadows" that move; one in response to the voltage driving the output stage, the other in response to the output power, I'll guess the R9, 25K sets the wink level of the indicator to correspond to full wattage output.
Unsure why the have separate indicators for the output stage drive and the output power. I wonder what the user manual would say?
Cropping a picture of one for sale on Reverb, the designations read "Overload Indicator" and "Volume Indicator" -
Unsure why the have separate indicators for the output stage drive and the output power. I wonder what the user manual would say?
Cropping a picture of one for sale on Reverb, the designations read "Overload Indicator" and "Volume Indicator" -
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Oh, the 6AF6 is an indicator tube! I should have looked it up first. I was wondering why 6AF6 has two control grids! So it's comparing between two signals, the output and the driver, to alert overloading, I guess?
I've seen those tubes off and on for so many years and it never occurred to me that there were two independent sections. Somehow I doubt they were thinking Stereo when they designed it. Maybe I'm confusing this tube with the 6E5...maybe I've never even seen a 6AF6, or didnt know it when I saw one.
https://www.radiomuseum.org/forum/the_optimal_use_of_the_6af6g.html