On Thursday, February 2, 2017 at 4:33:51 PM UTC-5, wrote:

Perhaps those who've restored a bunch of these can comment if they actually did dynamic testing of the capacitors.

I have done a fair number of AK55s and their Radiola and other-brand contemporaries, using potted 1 & 2 uF paper caps. I will typically test them at 500VAC on a proper full-voltage cap tester.

I have never, repeat, never found a bad potted paper cap in an undamaged device. The secret, in my opinion, is that the caps are massive (I have unpotted a couple for the sake of curiosity from rusted-out hulks), with wide clearances. The potting tar makes for an excellent seal as well.

Peter Wieck
Melrose Park, PA