Tube Rectifier Power Supply with No Load

[Zarrir]

Hi there Amptweakers!  How long can a high voltage tube rectifier power supply stay ON without a load? What happens if this mistake is commited?

[PRR]

If the caps are not sitting over rated voltage, forever.

A rough analogy: how long can I keep my water turned off while the water company maintains pressure? Pretty much forever.

Yes, if the supply makes 420V loaded and 470V no-load, and you used 450V caps, it may take hundreds of start-up surges to 465V and back to 420V loaded, but won't stand 470V no-load for very long before the cap blows up.

[Zarrir]

Thanks PRR, concise and spot-on.  I was concerned about the tubes lives.