I can only go by my own experience using 845 tubes by Amperex, United, Metal plate 845W, 845C, 845M, and the Shugaung 845B and standard 845. You should not witness a red glow when the tube is powered up. If the red glow can "fight" though the sea of white light, the plate is too hot. Once the tube is powered off, the plates glow red BUT the glow should not last 25 minutes!!! The red glow in my amps may last a minute.
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