85 deg C capacitor--advisable for VTA board?

I was curious whether using a capacitor (polystyrene) with an 85 degree Celsius rating was advisable, if mounted to the underside of the VTA board? I'm not sure how warm the parts get in this area.

Thanks,

Take a look at this helpful picture Bob Latino posted, showing VTA ST-120 temperatures using KT-120 output tubes.

https://dynacotubeaudio.forumotion.com/t828-tube-amps-get-pretty-warm-especially-in-the-summer-photo

Note the temperature of the two "Orange drop" caps averages 106 ºF, which converts to about 41 ºC. Your 85 ºC rated caps, mounted under the board (where temperatures will be even cooler) will be fine. I'm also assuming these caps will be used in the feedback network, toward the "front" of the amp.

Make sure you use heat-sinks when soldering them in, and be careful with cleaning solvents. Polystyrenes can melt easily, both from heat, and some types of electronic cleaning sprays.

Shovel, thank you very much. I had forgotten about that helpful pic showing the temperatures. And thanks for the reminder about polystyrene--I was going to use alligator clips for a "heatsink." Do you recommend anything better?