Zenith C845 - loud white noise on FM, ground buzz on AM

[Jeffhs]

Hi all -

My Zenith C845 AM/FM hi-fi radio quit on me yesterday. I hear very loud white noise on FM, no stations, and can only get one local station, very weakly, on AM. (There is a loud "ground buzz" sound all across the AM dial as well.) The radio was working perfectly well until yesterday evening. The FM and AM antennas are connected. I tried substituting a couple of tubes; no luck. I don't have replacements for the RF amp (6BJ6) or the FM converter (12AT7), so these tubes are still the originals. Are there readily-available substitutes for these two tubes? Took the bottom cover off the chassis, didn't see anything out of the ordinary. This set has about a half-dozen wax paper capacitors in it, one of which is behind a couple of other parts, so replacing it could be a problem. I am aware that this radio, being 51 years old (made in 1960), badly needs a recap; I'm willing to do that, but before I take that step I'd like to know if there is anything less drastic I can do to get the FM working again. This is one of the best sounding radios I own (second only to my Zenith K731), so I'd like to get it singing again as it was before last night.

Thanks in advance.