Tube Amp - Standby Switch Position

[fazer]

I'm sorry that was not my intention, and you are right about users' expectations. But, still, standby switches do more harm than good. I am always baffled that people still regard them as necessary

No need to be sorry when your right. It’s just convention to have a standby. Wasn’t the standby switch to protect expensive transmitter tubes or something? Just not really necessary for guitar tubes IMO , and the switch is a weak link in the B+ power supply chain.
All my old amps have standby switches and I plan to keep them for vintage quality, but I did have problem with an old bassman that came back to bad contacts on an old original Carling Standby Switch.

As CJ Said, switching the cathode on the powertubes is great way to standby with low current usually in the millamp range and lower voltage. Also if using quad powertubes provides an option for 1/2 power or even for changing to different sets of powertubes like. EL84 to 6V6. Or swap 6L6 to EL34 set. (using quad output tubes with only one or the other set active. Think El84 to 6V6.

As far as an internal standby covention for tube amp service, Seems like a weak link for more contact problems over time. It’s assumed if you service tube amps you are aware of high Voltage and learn the proper way to protect yourself by say, keep one hand in your back pocket and such to avoid being shocked across your heart from say one hand to the next. I would say we have all been shocked before by a tube amp that we have worked on. It comes with the life of serviceman to work smartly when working with high voltage. Personally I recently got shocked from the standby switch where I went to turn it on in an open fender chassis and with my thumb hitting the contacts while my fingers from the same hand touched the chassis. Been a while but it happens. Shame on me. If you are afraid you should not be opening the amp up. Just protect yourself and be very carful when working on anything over 450volts . It’s Technique that your taught and learn. Sometime the hard way.

 

[ccaudle]

no standby and applying full unloaded HT volts to cold valves damages the cathodes

That sounds like something that should be handled in the power supply design, not relying on the user to remember to start up properly.
On 1960's designs it might have been a problem, but a modern design or retrofit redesign of an older power supply should be able to handle that relatively easily.
I'm not experienced in tube behavior, what kind of delay time would be needed to give the tubes time to warm up? Sub-second, few second, tens of seconds?
With tube rectifiers was that handled implicitly by the warm up behavior of the rectifier tubes? Probably off-topic to the original post, but seems like replacing the standby switch with a small board with a 555 and solid-state relay running from the heater supply would be a good investment if putting power directly to a cold tube is such a problem.

 

[fazer]

power tubes need to always have. Neg bias voltage on grids. Standby should not disable the bias voltage. It can cause a surge that can blow fuses.

 

[Whoops]

My Roland Bolt 60 Standby Switch was modified in 2016 for Position number 2 in the drawing in the first post.
That's a mod that I advice to any Bolt 60 amp owner, and with that my goal with this thread was concluded.

Thanks PRR