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Old 19th Feb 2023, 8:53 pm   #117
ms660
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Join Date: Apr 2011
Location: Cornwall, UK.
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Default Re: What did I get myself into? Murphy A40C.

Quote:
Originally Posted by Katar83 View Post
Thanks, will go over it, see if I can understand anything out of it!
No problem, basically when the interstation mute is operating, V5's suppressor grid (g3) is made -ve with respect to V5's cathode, the -ve voltage is developed across the two resistors in the cathode circuit (R24 & R25) the voltage developed across them will be approx. 20 Volts, the bottom end of the cathode resistor R25 is connected to ground as is V5's suppressor grid via R26, the switches, R43 and R42, the cathode of V5 is approx. 20 Volts +ve with respect to ground which means that V5's suppressor grid is 20 Volts -ve with respect to the cathode, -ve 20 Volts on the suppressor grid with respect to the cathode is enough to cut off the current flow to the anode, hence the inter-station noise is muted, the valve data for the AC/SP1 (V5) can be seen via the link shown below, it includes information about using g3 (the suppressor grid) for noise suppression and details of g3's cut off voltage etc:

http://www.r-type.org/pdfs/ac-sp1.pdf

Lawrence.
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