Returning to the question of how to make a new power supply for a R1155 (or indeed any similar valve receiver) I have already given my own solution to the problem - but I had the luxury of newly made iron-cored wound components (transformer and choke) to any spec that I wanted. What do we do if that is not available - and we don't want to pay the going rate for newly wound parts?
One approach is to scour the rallies (when there are any!), ask people to turn out their junk boxes and possibly scavenge the parts from some junk valve radio. Many domestic sets from the 30s, 40s and 50s will have a mains transformer designed to produce a HT rail of around 200 - 250V. That is likely to be fine for a current demand of 75mA or so. Of course, this takes a fair amount of technical expertise in assessing "one-off finds" as to whether they are suitable or not. Many people don't have the confidence to do that.
That approach is likely to be less good for the heater voltage requirement, which is 6.3V AC at about 4 amps - if you leave the DF valves out. As far as I know, that's a bit high for your average scavenged domestic radio mains transformer. One alternative is to buy a separate heater transformer. A typical offering would be the first offering on
this supplier's page, which is a 230V mains tranformer with 2 x 6V secondaries, with a total power of 50VA. Cost is £16.66 plus postage.
I would run the two secondaries in parallel to give a total current capability of 8A or so. With 240V going into a 230V primary, and the transformer lightly loaded, the actual voltage is likely to be close to the required 6.3V. I would still use chunky wire to minimise voltage drops between the PSU and set though, along with the original Jones plugs, which should keep losses as low as possible.
When it comes to buying a brand new transformer for the HT rail, it seems to be near impossible to find anything like a 250V secondary. The highest secondary voltage RS offers in chassis mounted transformers is 50V. That could be voltage quadrupled up to 200V. They offer a toroidal transformer at 115V output, but that costs over £50. I see Cricklewood Electronics offer
this toroidal transformer which will do 70V AC, but that still costs near £30, probably because its total overkill for our purpose here at 160VA rating (we only need about 20VA!). And it will still need a voltage tripler to get our 210V rail.
Conclusion: its technically possible to design a brand new psu using off-the-shelf readily available parts, but it won't be cheap. Somewhere between £50 and £100 in parts alone, most of which will be the transformers.
Now we know why simple PSUs suitable for this purpose offered on Ebay are snapped up like hot cakes, and fetch "silly" prices!
Richard