Quote:
Originally Posted by alanworland
Thanks, I could understand that if the cap was wired across the contacts to help prevent/reduce arcing but this was wired across the load side of the double pole switch?
Do I even need it?
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It was not there on early ones I believe. It was almost certainly added to stop the switch off click as Ron says.
The switch off arc is caused because the transformer is an inductor.
And an inductor 'stores' energy by magnetism. Very simplistically, if you happen to switch off just as the voltage of the mains cycle is at its highest, the transformer core will also be magnetised to its greatest, now as that magnetism fades very quickly, it causes a high voltage to be produced, enough to jump the switch gap, the arc. If you add a small capacitor or snubber across the transformer or the switch, the capacitor 'soaks up' the electricity preventing the arc.
Your 44 has a double pole mains switch, so fitting the 'snubber' across the transformer is logical. It prevents or greatly reduces the arc and is only in circuit when the unit is powered.
Where single pole mains switches are used the snubber is normally across the switch. But that can cause problems because the snubber is always at mains voltage and 'leaking' a small current into the equipment when it is switched off. Dangerous if you assume it is switched off and so isolated from the mains, worse if the snubber is faulty and you assume the same thing...
Sorry if you already understood this, Alan