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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? Admiral Radio Internals, circle around to green caps with powdery white residue

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.

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  • \$\begingroup\$ I think those are green poly dip film capacitors and the white powder does, in fact, indicate a problem with them. It's likely tantalum oxide crystals (as I don't think it is easy to create such large aluminum oxide (sapphire) crystals there.) I'd replace those. \$\endgroup\$
    – jonk
    Commented Oct 28, 2022 at 5:54

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The capacitors may not be damaged in spite of the powdery residue on the encapsulation.

The most likely cause of the set remaining dead could be the damaged on / off switch on the potentiometer (its contact remaining open even after it is actuated).

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I think it's unlikely there's anything wrong with those epoxy-dipped polyester caps.

And dried out electrolytics might not cause the radio to not emit any sound at all (it's possible with coupling caps, but those usually don't dry out as much as power supply caps).

I'd look for mechanical causes first, probe voltages and look for possible cracks in that brittle phenolic PCB material, lifted pads and broken solder joints. And I would do that before picking up a soldering iron. It's a lot easier to work with something that's working imperfectly (most likely due to a single main cause) than to touch a dozen things and wonder why it still is dead (maybe now due to multiple issues).

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