RUBLI HTR-214

As Featured in AudioXpress (formerly Glass Audio) magazine, Agust 2001, page 50, See article

A whole new approach for protecting your valuable Tubes.

Revision "A" Board

New revision "B" Board !!!

You know that applying high voltage to your tubes BEFORE they have reached their working temperature causes cathode stripping, You are also aware that new made tubes are more delicate than NOS tubes, and that NOS tubes are getting more and more expensive ...
You also know that installing a device preventing this disease is cumbersome, and expensive, such as installing a pcboard with relay and transformer. yes, drilling a hole to put a standby switch into the valuable, mint faceplate is a crazy idea .
Or you can drill a big one inch hole to put a tube as a delay , but hey, you also need to put another transformer, 6D22 or 5AR4 draws a LOT of current.
Yes, you know all that, but you still have your amp with a superb diode powersupply, but you are threatening the life of your tubes, the output tubes more than all.
This tiny PCB, has only TWO terminals, and it goes in series of the HV supply. No need for cable runs, transformers or relays and no conection to ground.
This circuit contains a SCR, that once triggered after 40 seconds, makes all other components electrically dissapear from the electronic circuit. This SCR , once triggered to the ON state will drop 0.7 volts of your power supply. (less than 0.1 %)
Out of the shelf, this circuit works in amplifiers with a HV of 350-550, but it can easily modified for lower voltages, or by changing some components, it will work on a 850 HV

AudioXpress Article Aug, 2001