01-12-2016, 08:17 PM
Hi.
In addition to my last couple of posts, id like to say that using a cap dropper for either heaters or HT should not be a worry. Modern run caps are really reliable especially in this use where they are lightly loaded and not subject to inductive or heavy loads from stationary motors or big pulses from motors being switched off and other switching that is on motors with separate start and run caps.
The addition of a discharge resistor in parallel with the capacitor should always be done, a 100k across the heater cap is fine or a 470k across the HT cap will also be be fine.
I have two Murphy TV's with cap droppers, a V330 & V530, the original design uses a 441 ohm dropper resistor for the heater chain when VHF FM Radio is selected, these 441 ohm resistors get mighty hot and in the V530 it causes the EHT rectifier valve base to degrade.
So in these sets I have a main heater chan dropper cap and a secondary one for the radio chain when it is switched over.
In this case I use a 27k resistor across each cap to reduce sparking on the Radio/TV slide switch. Both sets have been 100% reliable with the caps and the V530 is used for hours on end on Radio with a massive reduction of heat.
In addition to my last couple of posts, id like to say that using a cap dropper for either heaters or HT should not be a worry. Modern run caps are really reliable especially in this use where they are lightly loaded and not subject to inductive or heavy loads from stationary motors or big pulses from motors being switched off and other switching that is on motors with separate start and run caps.
The addition of a discharge resistor in parallel with the capacitor should always be done, a 100k across the heater cap is fine or a 470k across the HT cap will also be be fine.
I have two Murphy TV's with cap droppers, a V330 & V530, the original design uses a 441 ohm dropper resistor for the heater chain when VHF FM Radio is selected, these 441 ohm resistors get mighty hot and in the V530 it causes the EHT rectifier valve base to degrade.
So in these sets I have a main heater chan dropper cap and a secondary one for the radio chain when it is switched over.
In this case I use a 27k resistor across each cap to reduce sparking on the Radio/TV slide switch. Both sets have been 100% reliable with the caps and the V530 is used for hours on end on Radio with a massive reduction of heat.
