I just opened up an old Admiral Model Y2301GPN pocket radio from the 1960s (schematics). It not working at all, no signs of life when I power it on. I'm waiting on a new multimeter to be delivered, so I haven't tested any caps yet, but these capacitors (C13 and C15 in the schematic) look strange with a powdery residue on them. I haven't seen just two capacitors look like this when the rest of the board looks pretty clean, especially since i think these are film caps, not electrolytic (i already planned on replacing all the electrolytics). Any ideas what this is? Is it a sign of capacitor failure?
Edit: After a lot of searching I found a forum post about this that featured a helpful video. It didn't really answer the question of why this happens, but does seem to cause the capacitors to become brittle and unreliable, so I'll go ahead and order replacements for my "moldy" capacitors.
Edit 2: Ended up being a broken solder joint - fix that and the radio played. Then replaced the electrolytics, that improved the sound quality. Didn't replace these capacitors, but have spared on hand in case I want to later.