01-08-2020, 01:50 PM
(This post was last modified: 01-08-2020, 02:03 PM by Mike Watterson.)
The tuning rotor, the shaft, IS potentially live as it goes direct to the chassis.
The "RF live" bits are the stator. Trimmers too are usually wired with the slot head/moving part to OV and the fixed part to RF, built-in on tuning gangs or standalone.
The switch shaft being live is maybe more likely than the volume control, but not particularly due to the chassis path of L9.
The switch itself also switches one side of the mains OR the -HT battery to chassis. The +LT battery or the ballast resistor is switched by another part of that switch to the filament chain.
The power switch on the volume control is disconnecting the LT- of the battery and the -ve HT from the band switch, which is either the -ve from the battery or direct to the mains cable.
So no matter which way you wire the mains lead, the band switch has a direct connection to mains on two pins and the other side of the mains via a rectifier HT dropper to 85V and ballast resistor to two contacts on Sw1c. I measured 320V DC between the R12 ballast switch contacts and the end of the mains lead that goes to SW1D pair of mains contacts. No doubt 230V AC peak via the rectifier and stray capacitance to the 20 MΩ input impedance DMM.
So while an interesting idea; the C5a does nothing for safety of the wave change switch shaft or the tuning shaft.
I've quite a few sets with the crazy combined wave change and battery/mains, including some Pye models. The Pye made Invicta I have though has a separate three way switch styled like a toggle switch. Philips and many USA sets had the battery/mains switch on a dock for the mains plug. One USA model has to have the original size and shape of 110V two blade plug as it has a spring loaded drum for the mains cable and it can't retract fully and operate the switch unless everything fits properly.
The "RF live" bits are the stator. Trimmers too are usually wired with the slot head/moving part to OV and the fixed part to RF, built-in on tuning gangs or standalone.
The switch shaft being live is maybe more likely than the volume control, but not particularly due to the chassis path of L9.
The switch itself also switches one side of the mains OR the -HT battery to chassis. The +LT battery or the ballast resistor is switched by another part of that switch to the filament chain.
The power switch on the volume control is disconnecting the LT- of the battery and the -ve HT from the band switch, which is either the -ve from the battery or direct to the mains cable.
So no matter which way you wire the mains lead, the band switch has a direct connection to mains on two pins and the other side of the mains via a rectifier HT dropper to 85V and ballast resistor to two contacts on Sw1c. I measured 320V DC between the R12 ballast switch contacts and the end of the mains lead that goes to SW1D pair of mains contacts. No doubt 230V AC peak via the rectifier and stray capacitance to the 20 MΩ input impedance DMM.
So while an interesting idea; the C5a does nothing for safety of the wave change switch shaft or the tuning shaft.
I've quite a few sets with the crazy combined wave change and battery/mains, including some Pye models. The Pye made Invicta I have though has a separate three way switch styled like a toggle switch. Philips and many USA sets had the battery/mains switch on a dock for the mains plug. One USA model has to have the original size and shape of 110V two blade plug as it has a spring loaded drum for the mains cable and it can't retract fully and operate the switch unless everything fits properly.
