This is a simple QRP transmitter modeled after a schematic from and OLD ARRL handbook. Maybe its the glow of the tubes or the heat they produce.
After reading some horror stories about cracked tubes I added a Dallas 18B20 temp sensor to the water supply.
I have a bunch of Peltier chips and heatsinks and a small pc cooing radiator but so far the temp hasn’t come near 70 and its been a really hot summer. I don’t know if I’m going to need any supplemental cooling.