I am currently restoring this radio.
An AC mains version of the TRF radio Kobra 274
which I restored a little while ago.
It looks all to be very original, and the most amazing thing is the 1931 capacitors in it all test as working very well. There is a large metal can capacitor block, it is labelled as 10.1uF. It is actually made up of 4uF 4uF 2uF and a 0.1uF. None of them draw any more than about 0.05mA at 350v and they all have lower ESR readings than any of my new components. They are also holding a charge well, so they will be left in circuit.
There is also 2x 1uF capacitor cans marked Kolster Brandes, these also have a very good result on the ESR meter and leakage current. The only capacitor that I will be replacing, when I get one, is a 200pF wax paper that shows a little too much leakage and as it is used to connect the aerial to the mains it will need a new one fitted, at the moment it is disconnected.
The mains transformer tested out as working well, as with the OP transformer.
There is no intervalve transformers so no problems there.
There is an on/off switch missing off the side, and a small paxolin strip which is a push fit into a lever which turns a coil in another coil. No problem there as trimmed Magnum lolly stick fits perfectly.
There is only one real problem and that is the energising coil for the speaker is open circuit. But using a replacement speaker I have found the radio works reasonably well as can be expected for a simple circuit like this.
I am looking for a circuit for the radio, cant seem to find one anywhere, I have PM'ed a couple of members on UKVRR who were talking about having the circuit back in 2010, but dont hold out much hope as they have not posted in the last 4 years. Has anyone on here got one?