T-storm just came through so ambient temperature okay for a repeat test. Here are some more data points on the Puretone. Metal considerably cooler than the tube tops but still hot. Hot air flowing up through grill measured at metal surface level is 10˚C hotter. IR data are not accurate, except maybe on the tolex, which approximates a black body.I would love to see this same experiment but with the thermocouple on the metal grill. If the temperature comes anywhere close to 100ºC on that grill, I would definitely be using a fan.
Thanks for a helpful demo!!