I'm thinking #35 acts like a noise suppression cap that is placed across the line. It us a small enough value to be able to pass hash on the ac line but not much 60 hz component into the dc power supply!
Ron
The reason I mention it is that I had a set that was recapped by someone that miss wire a cap in this fashion. Should have been across the line not across the rectifier. It had a terrible hum. After checking the tubes for shorts and the filter caps I saw a cap across the 25Z5 socket wasn't shown on the diagram wired like that. Rewired it to B- and all was well.
I know I've seen another set wired like this that I've worked on, can't remember brand or model. Maybe your cap is fairly leaky. No harm in rewiring it across the line with appropriate X safety cap.
Ron
I see no good reason for that cap. I would try the radio with and without the capacitor.
Steve