Does any one owns tube portable radios that have F.M.?

[Josef]

Nice radio, but the heater cell looks extremly cappy too. Fortunately Mr. Heigel, a well known collector here in Austria developed a quite simple but effective replacement circuit:
Just replace the cell with an 4700uF cap and parallel two diodes connected in series with each other to the cap producing stable 1,4V:

https://www.radiomuseum.org/r/radione_r20.html

[Electronic M]

Funny, about a week ago I got the Grundig working and I pulled out the ancient NiCad rechargeable A supply cell and replaced it with a 4700uF cap. In addition to the hard wired in NiCad it had battery clips for installing a standard off the shelf D cell. I figured out the D cell does okay voltage regulation (slowly climbs over a few minutes).
Instead of the diodes I'm going to hunt down a modern NiCad cell and replace the original.

The set had no audio initially because the NiCad in it had leaked and corroded the AC mode output tube heater ground open. This set interestingly has 2 single ended output stages because so it can have loud output on AC and low power consumption on battery...I had only seen that on 40s american sets till now.

Besides those issues it only had a handful of bad lytics.

Till I get another NiCad I plan to run it off batteries primarily.

[Josef]

If you plan to run the radio from batteries only this ist totally fine.
If you run it from mains, it needs the diodes or a new battery to avoid blowing the tube filaments from overvoltage.
The advantage of the diode circuit is: it will last forever- a new battery will fail again sooner or later

BTW: This portable radio has two output tubes too for the same reason you already mentioned:

https://www.radiomuseum.org/r/radione_r20.html

Edit: Of course the Radione R20 only has one AF output tube but this radio has two:

https://www.radiomuseum.org/r/minerv...able_531f.html