Its awkward to change series resistors and zeners to vary the Ht voltage off a regular passive mains transformer/bridge/filter supply for test purposes.
Instead , how about using your programable bench top arb gen to drive a standard step down transformer in reverse
and generate a variable HT voltage . Smoothing can be done in the traditional way , RC , but for the sake of 13 euros worth of a hammond choke(150H/8mA) , worth putting some Henries into the equation to make sure your reference voltage is down to a few uV noise .
The output of the gen can be trimmed under load and stored as a preset , you can dial in the anode voltage to a very fine degree of precision on a given tube and snapshot it if you want
Of course your not limited to the usual 50/60/100/120hz residual hum from mains opperation either , swap out the iron core for ferrite and square wave/saturate into the Mhz region if thats what tingles your fancy .
Instead , how about using your programable bench top arb gen to drive a standard step down transformer in reverse
and generate a variable HT voltage . Smoothing can be done in the traditional way , RC , but for the sake of 13 euros worth of a hammond choke(150H/8mA) , worth putting some Henries into the equation to make sure your reference voltage is down to a few uV noise .
The output of the gen can be trimmed under load and stored as a preset , you can dial in the anode voltage to a very fine degree of precision on a given tube and snapshot it if you want
Of course your not limited to the usual 50/60/100/120hz residual hum from mains opperation either , swap out the iron core for ferrite and square wave/saturate into the Mhz region if thats what tingles your fancy .