[SteveCG]

I've dealt with a Ferrograph Series 2 and its 'paper' capacitors were electrically leaky - although they looked alright visually. I've been told though that the Series 4 used better capacitors and they may not be leaky - however this information should not be relied upon without checking them.

I've never dealt with a Series 4, but it looks a lot like a Series 2, in which case, as Radio_Wrangler advises, you will need to regrease the mechanics. Remember to keep grease and oil off the rubber idlers.