Are you aware that these are classed as 'communication receivers'? They have extra functions/controls that are of no use with normal broadcasts. They are more complex and considerably more difficult to work on than a standard broadcast receiver. They are still quite popular with enthusiasts (I have one) and have recently overhauled it, not without some difficulties. They also use a 'Universal' power supply arrangement and don't have a mains transformer. Instead they use a dropper arrangement with a series/parallel heater chain......not for the fainthearted. Although the outer enclosure is earthed, the rest of the chassis could be live. It's essential to use an isolating transformer when working on them particularly if alignment is required.
Basically they are a bit more than just an 'oldie valve radio'.
Here is the restoration of my 840C.
https://www.vintage-radio.net/forum/...d.php?t=194713
Still not quite finished.