Speaking of “sources of heat”, aside from my CTC-16XL & FADA 895, & Stromberg Carlson x-21 m4b, and soon to finish GE CTC-15&1/2 clone, I have sevral others in storage to play with in the future, like the rm 503 oscilloscope, also on the list are 2 dynakit mark III amps, a Sansui 1000 amp, and someplace hidden in my parents attic is a small 6v6 amp of my dad's I hope to find some day. ( he passed in 2011, so I can't ask where he hid it )
And I will say it again, I really wish he had not gotten rid of that CTC-10A sullivan when I was very young.
And, I wish I kept the rca ctc 38 from my gradparents, it fried the FBT, and I dumped it, I was a dumb teen
But the stuff I do have working now, does warm the place up a bit!