Standby Switch in Dumble schematics

[Gerrit666]

I do not like to raise another discussion about standby switches and if they are useful or not, but I like to understand the advantages and disadvantages of different kind of implementations.

Most Dumble schematics with an SS show them between first filter caps and choke. Due to Merlins guidelines this a not a good position. First it is switching pure DC (around 440V and 150mA) and it is placed directly before the choke. Both should be avoided. Sure, we can use a DPST switch and halfen the current and add a RC-Unit to avoid sparks if this helps.

Some Dumble schematics show the SS after the rectifier and before the first filter caps. Due to Merlin this is the preferred position for a FWR. Additionally (but missing on the Dumble schematics) he put a 1MOhm resistor to ground for switching reference and another diode after the SS (http://www.valvewizard.co.uk/standby.html)

Another recommended position for a SS in combination with solid state rectifier is to put the SS between PT and rectifier. This is found in Dumble schematics very rarely (see image attached). Here we only switch AC but need a DPST to switch both legs with the rectifiers. Why is this seen so rarely? Is it because of having around 680VAC on the switch (while the switch is only switching 340VAC and aound 300mA, right?).

What are your thoughts?

[jelle]

Mods, please move this discussion to the discussion section.

Also what is SS, the abbreviation was not clarified in the post.

[erwin_ve]

Also what is SS, the abbreviation was not clarified in the post.

Standby Switch.

[pompeiisneaks]

Mods, please move this discussion to the discussion section.

Also what is SS, the abbreviation was not clarified in the post.

Moved to Dumble Discussion.