Save your tubes with a better Standby switch?

[SpiderWars]

Here is a Valve Wizard article regarding Standby Switches. I recently bought a Franklyn Amps Tweed Bassman 5F6A clone and this amp has a resistor across the Standby switch and I hadn't seen that before. The article explains it. I like this mod and think I might do it to a lot of my amps. It allegedly prevents cathode poisoning from extended time on Standby.

I still use Standby on my SS rectified amps but my tube rectified amps just get turned on.

 

[scottosan]

Here is a Valve Wizard article regarding Standby Switches. I recently bought a Franklyn Amps Tweed Bassman 5F6A clone and this amp has a resistor across the Standby switch and I hadn't seen that before. The article explains it. I like this mod and think I might do it to a lot of my amps. It allegedly prevents cathode poisoning from extended time on Standby.

I still use Standby on my SS rectified amps but my tube rectified amps just get turned on.

In most amp designs, a standby switch is not even necessary. It’s more of an expected feature. Where I can see it being necessity is in under-designed amps with improperly spec’d power caps that can’t handle the elevated B+ before the tubes get warm enough to start drawing current and dropping the B+

 

[SpiderWars]

In most amp designs, a standby switch is not even necessary. It’s more of an expected feature. Where I can see it being necessity is in under-designed amps with improperly spec’d power caps that can’t handle the elevated B+ before the tubes get warm enough to start drawing current and dropping the B+

What is weird is that this 5F6A clone had all the filter caps after the SB switch so NOT using the Standby was by far better than using it. It had bias voltage in SB but all the filter caps were after the SB switch. It just involved switching a couple of wires and everything is right there so it only took a few minutes.

The filter caps are 500v rated and they get to 475vdc on SB with my 124vac wall power so it should be fine there.

 

[Fusionbear]

I install standby switches in my builds, but never use them. They are not necessary.

 

[SpiderWars]

I install standby switches in my builds, but never use them. They are not necessary.

Right but other people do use them and sometimes leave the amp on Standby for extended periods. I know I've mistakenly left amps on overnight and sometimes on Standby. I like that a cheap resistor can potentially prevent interface resistance. Whether or not interface resistance is an issue is debatable but per the article it is one of the few things we should be worried about wrt Standby switches.

 

[glpg80]

I am all for a standby switch that is completely isolating the tubes from any plate voltage because I want to give the grid bias circuit enough time to correctly turn the valves off at idle before plate current is allowed - it’s this initial wide open throttle instance where the tube has to burnish all of the plate current until the capacitors are initially charged - also lengthening the charge time the screen and B+ capacitors need to reach initial charge.

Also standby switches allow for testing of certain circuits for correct functionality - this is more tech preference than anything.

Mine will stay completely isolated and I never leave an amp in standby for long periods (hours) as mentioned in the article. I also don’t have tube rectifiers which is a mute point for flyback concerns.