Thanks to both cbarn24050 and ScottyUK...
I ceratinly have no great expecttaions on quality from this vintage amp - though when I used one through the 70's as a guitaer practice amp, it was the dog's nuts!
The cap (ScottyUK) was a 1000uf, not 10,000uf, so I'll be heading on a 1000-2200uf...