I have all DHT monoblocks with SE-PX25M/PP-2A3M/PP-520B Plitron OPT on end. The tubes have been working since 2005 great.
I have a radiation thermometer and this can measure through the glass temperature of anode plates. The plates have highest temp on top.
I measured 188-195C on 520B /115mA-470V/
102-107C on 2A3M /45mA-225V/
70-72C on PX25M /24mA-240V/
My question is, what would be minimum and maximum operating temp of these tube plates?
Does exist optimal temperature on plates, according to life time also?