07-07-2018, 09:03 AM
I'm having second thoughts about the theory of operation of the DR31 system switch.
Consider rotary switch SW13: When the VHF channel selector is turned the connection between the junction of the chokes and the sliders of SW3 and SW6 is well and truly broken. This would leave the capacitor C65 isolated until contact with either solenoid is established again when a VHF channel is selected.
So it follows is the 0.25microfarad capacitor an active component in the operation of the system switch?
Perhaps what we read in the Trader service sheet is the author's interpretation on how the circuit works.
C65 is now shown as 0.25uF and not 0.25mF. Can you imagine a 0.25millifarad capacitor in a TV set of 1963? My apologies for using the archaic term mF for microfarad.
Anyway, Decca abandoned that system switch circuit and replaced it with a simpler arrangement in which only one of the two solenoids is activated to move the armature.
Geordie McBoyne.
Consider rotary switch SW13: When the VHF channel selector is turned the connection between the junction of the chokes and the sliders of SW3 and SW6 is well and truly broken. This would leave the capacitor C65 isolated until contact with either solenoid is established again when a VHF channel is selected.
So it follows is the 0.25microfarad capacitor an active component in the operation of the system switch?
Perhaps what we read in the Trader service sheet is the author's interpretation on how the circuit works.
C65 is now shown as 0.25uF and not 0.25mF. Can you imagine a 0.25millifarad capacitor in a TV set of 1963? My apologies for using the archaic term mF for microfarad.
Anyway, Decca abandoned that system switch circuit and replaced it with a simpler arrangement in which only one of the two solenoids is activated to move the armature.
Geordie McBoyne.
