I'm thinking about re-stuffing new electrolytic bypass caps in the old 20uF paper tubes in a small 1955 chassis (GA9, 2x6V6 parallel SE, if it matters). In some experiments and reading it sounds like you can re-seal the ends of the stuffed tubes with melted beeswax. BTW, these antique radio pages contain an almost-overwhelming amount of info -- everything you might ever want to know -- about old caps. https://antiqueradio.org/recap.htm https://antiqueradio.org/col01.htm But beeswax has a nominal melting point around 144-147°F. So I got to wondering how hot it gets inside a tube amp chassis. Obviously hotter near the PT and power tubes, and obviously it varies by amp, chassis size, and chassis ventilation. 4x6L6? Overworked old PT? etc. I've seen thermal imaging data of PTs getting pretty hot, but luckily the re-stuffed caps are down the other end from the PT in this amp. Data wiz @peteb shared some measurements (from a Champ, Pete?) that in the actual circuit temps got up to 150° (for example near the cathode cap and rectifier) but the chassis near the PT only got up to 90°. If the latter temp governed the air temp, beeswax might be fine, but if convection or (more likely) radiation heating brought the re-stuffed caps up toward 140... well, ugly. So have any of you ever measured the temp inside a buttoned up tube amp chassis?