John-Del wrote:
On Wednesday, August 9, 2017 at 2:43:55 PM UTC-4, Michael Terrell wrote:
John-Del wrote:
On Thursday, August 3, 2017 at 12:16:59 AM UTC-4, wrote:


If you really must restore some old thing to its original, unsafe and inefficient state, by all means do so. But don't come crying to me if it burns your house down. Mainly, don't fall asleep with the thing running.


If you're referring to the resistance line cord in my example, there aren't many options even if you don't care about originality (I don't). That radio in my example has 5 tubes, two IF XFRs, a gang tuner and a dynamic speaker all crammed into a 4X10 chassis pan. The plastic cabinet covers this like a glove. There's simply no room to mount a 25W resistor or mitigate the heat that it produces.

Still, in the trade, the resistive AC line cord was known as a "curtain burners" because people would often coil them up in a neat little ball instead of spreading them out as the owner's manual directed.

I do restore an occasional antique radio for my customers, and even after adding fuses and polarized line cords to them, I instruct them on the dangers of line connected metal chassis and never plug in the radio if one of the plastic knobs falls off. I also instruct them to leave all old radios unplugged when not in use and to not leave them running unattended.


A small 'buck' configured transformer will reduce the filament
voltage without crating a lot of waste heat.



Two problems: 1) there's precious little room in the radio in question for even a small buck transformer and 2) these radios are series string and have no power transformer to buck...

I can understand a space problem, but you don't need a power
transformer, to add a buck transformer. It is a simple autotransformer
with the secondary wired anti phase, in series with the filaments. It is
tiny, since the secondary only has to be the proper voltage, and it will
handle the filament current. I've used them for decades, on both
electronics and industrial machine tools.



--
Never **** off an Engineer!

They don't get mad.

They don't get even.

They go for over unity! ;-)