Standby switch wiring...what do you prefer?

[dehughes]

I have read/heard that there are several ways to wire in a standby switch, and am curious as to how you all prefer to do this. My build is basically an AC30 with MM Woden trannies, 5AR4 recto, blah blah, etc....

Lemme know what you guys prefer/recommend....

MANY THANKS!


david

[Bob-I]

I like to break the HV line right after the first filter stage, but before the choke/resistor.

[dehughes]

I like to break the HV line right after the first filter stage, but before the choke/resistor.

Cool. Why is that?

Thanks!


david

[skyboltone]

Not as an amp builder but as transmitter and ham radio builder, I would prefer lifting the center tap of the transformer from ground where possible. The problem with this approach is that you still have high voltage across the two outside leads of the transformer. Don't mislead yourself into thinking that there is no potentially lethal voltage present. This is a standby switch only, not a "safe" switch. I don't like high voltage/high current in a set of breaking contacts.

[VacuumVoodoo]

Not as an amp builder but as transmitter and ham radio builder, I would prefer lifting the center tap of the transformer from ground where possible. The problem with this approach is that you still have high voltage across the two outside leads of the transformer. Don't mislead yourself into thinking that there is no potentially lethal voltage present. This is a standby switch only, not a "safe" switch. I don't like high voltage/high current in a set of breaking contacts.

This is also the prefered method to comply with electrical safety requirements. A switch can fail mechanically so that internal parts could make contact with chassis. Should this happen there is no high DC voltage present that would put the chassis on high DC potential. If you also put your B+ fuse in series with the standby switch this also adds to the safety as there will be no high DC potential on the fuse and no risk of arcing on the fuse holder.

[Moose]

I like to break the HV line right after the first filter stage, but before the choke/resistor.

Cool. Why is that?

Breaking B+ after the first filter caps but before the plates had the benefit of allowing those caps to charge when starting the amp, but isolating the preamp caps. This makes for a lower onrush current surge as the caps get their first charge.

Others have mentioned benefits of centertap switching.

[dehughes]

Very nice. Is there a schematic to this type of switching that you all could point me towards? I'm a newb at most of this, so a visual reference would be handy.

Thanks so much,


david

[Bob-I]

I like to break the HV line right after the first filter stage, but before the choke/resistor.

Cool. Why is that?

Breaking B+ after the first filter caps but before the plates had the benefit of allowing those caps to charge when starting the amp, but isolating the preamp caps. This makes for a lower onrush current surge as the caps get their first charge.

Others have mentioned benefits of centertap switching.

Yep

[Moose]

Very nice. Is there a schematic to this type of switching that you all could point me towards?

The express uses this method. Look at the layout and the Kelly schematics floating around this site.

[dehughes]

Very nice. Is there a schematic to this type of switching that you all could point me towards?

The express uses this method. Look at the layout and the Kelly schematics floating around this site.

Right on. Thanks.