[turretslug]

As the set looks in good and (thankfully) unbodged condition, being careful following a few capacitor changes will at least show whether it's worthwhile pursuing further overhaul. I've a 670A here with a very similar PSU/chassis arrangement (other than a selenium, rather than thermionic, rectifier), I use it with a 1:1 mains transformer. As the half-wave rectification used in both sets puts a DC component through the secondary, using a transformer with a generous VA rating is sensible, I use a 250VA ex-BT "Mains Conditioning Transformer"- these were available in large quantities very cheaply a while back but unfortunately the snake-oil folk have cottoned on to them and want lots of money now.

You might find a 230V 1:1 isolater (often red GRP container as opposed to yellow GRP as used for 110V "site" types) fairly cheaply- the set will work at 110V but 230V will give good HT for optimum performance.