OP, I would wonder on that one, myself. I’ve used thermal guns, sense they became available to mechanics. Take your readings at several different spots. The top may get the hottest, but that’s not the actual plates, wires or glass.
I suggest you put 6 dots on the valves, with a marker. I would aligned the marker dots with the pins. Upper, mid and lower on the valve in two marked spots per, Upper/Mid/Lower. I suggest a GOOD warm up AND playing at a given volume. I’d do a Low, Mid and High volume, test, too. When you collect your data, average, and see if thing look more in line. I suspect "Idling", is one set of numbers. Different loads, will change the temps, and the numbers will start looking closer.. Remember YOUR hand position too. If it's deck height and 6 " away. do the same for all. It's the most important part if you really want to know. "The reference" points, have to be the SAME.
The expensive valves you have, for the sake of keeping them looking good. Be careful removing your marks (if you do) Isopropyl can take off the silkscreen, or information on the glass valve, GEs, RCAs, Tellies, Volvos, Mazdas, (you know the powder wipes right off.)
Happy holiday, happy listening
Regards
I suggest you put 6 dots on the valves, with a marker. I would aligned the marker dots with the pins. Upper, mid and lower on the valve in two marked spots per, Upper/Mid/Lower. I suggest a GOOD warm up AND playing at a given volume. I’d do a Low, Mid and High volume, test, too. When you collect your data, average, and see if thing look more in line. I suspect "Idling", is one set of numbers. Different loads, will change the temps, and the numbers will start looking closer.. Remember YOUR hand position too. If it's deck height and 6 " away. do the same for all. It's the most important part if you really want to know. "The reference" points, have to be the SAME.
The expensive valves you have, for the sake of keeping them looking good. Be careful removing your marks (if you do) Isopropyl can take off the silkscreen, or information on the glass valve, GEs, RCAs, Tellies, Volvos, Mazdas, (you know the powder wipes right off.)
Happy holiday, happy listening
Regards