[cathoderay57]

Thanks for the replies. The odd one of these sets comes up at BVWS auctions from time to time but there don't seem as many about as the perhaps more affordable HMV and Marconiphone models with fewer valves and a KT63 or KT61 output valve. I note the Trader Sheet quotes a purchase price in 1937 of 19 Guineas which was a tidy sum then, I guess (I wasn't even a twinkle in my father's eye back then I hasten to add!). The U50 is definitely directly heated but from the look of it non-original although it has the coke bottle shape. I'll certainly have a think about using an SMPSU limiter or a bucking transformer - I had to google the term as I wasn't familiar with it, but I get it now. I have got a couple of 6.3v heater transformers in the junk box so I've probably got one that would do the job. Just slightly concerned because the 6.3v winding would not necessarily have been rated for mains to core isolation, with the mains winding connected in series anti-phase. I guess using a 5v rectifier winding would solve that issue. I have been into domestics this morning so haven't reassembled the set yet. Will do a photo later. Cheers, Jerry