Introduction
This radio was bought in June 2005. It looked reasonably well for its age. The oak casing had its normal wear in some places. The speaker cloth was faded by sunlight, but it was still original. The front of the radio, made of aluminium painted black, was in good shape.

As this is an old radio (1930) some things were missing as well. The back panel consisting of three oak segments and an aluminium segment for instance, but this is quite normal for this type of radio. The 506K rectifier was missing as well. It was replaced by diode rectifier (without an additional resistor!) and the rest of the valves (E447, REN904 en B443) were far from original. I spotted a choke coil that looked a bit to new, and in the area below the E447 I noticed some extra decoupling capacitors and resistors. The LF transformer seemed to be home made. Volume control was missing and someone had made a gramophone connexion in the right hand side of the cabinet.

In the picture, the green choke coil is visible below the wire that runs to the top of the E447. Next to this coil, also below the E447, a yellow mepolesco condenser can be seen. The 506K rectifier has to be mounted upside-down in the right hand corner above the E447. Volume control was not in its place to the right of the E447. The home made LF transformer is visible below the B443 and the REN 904.

 

The slotted grooves in the side of the cabinet are original and were made to accommodate the cables for power, antenna and earth (right) and an extra loudspeaker (left).
Chassis plate and rectifier

The brass strips have been partially restored. On the right a green resistor. Volume control is missing there. Just visible below the pertinax plate, a yellow mepolesco condenser.

 A nice detail in this radio is the brass strip wiring. It looks a bit like modern i.c. Alas, some of them were missing on top of the pertinax plate. To solve this problem the missing connections had been made underneath the chassis with nasty blue wire! In spite of all this, the radio was working reasonably well, although it was playing very loud, mainly because of the wrong valves and the missing volume control.

I started by making new strips. I found some thin brass plate and discovered that was very easy to cut. When all the strips were screwed back and connections were made, I could remove the blue connecting wire underneath.

The partially removed diode rectifiers.

 
I managed to buy a 506K rectifier at the NVHR meeting in Doorn. Not a new one, but still good enough for this radio. A support bracket for this valve was made. The diodes could be removed. Now I had to look for the rest of the valves, the Philips 4000 LF transformer and a 1K5 volume control.
In a spot were a  50 Ohm resistor had to be, the choke coil mentioned before was mounted. A nice way of improving selectivity a bit, but not original. It had to go!
The "wrong" valves from left to right: B443, REN904, E447. On the upper right the 506K rectifier has to be mounted upside-down. The Philips 2044 loudspeaker was not secured in some places. That was an easy one!
The next step was removing the unnecessary decoupling components in the E447 area and making a new brass strip. I still have to look for more original resistors.
Oak back panel
Because I had to wait for the valves and the Philips 4000 LF transformer, I could focus my attention to the back panel. In the city where I live, Utrecht, I found a small do-it-yourself store where someone was willing to make the three segments to measure. Ammonia was used to age the wood a little bit; after that a little pickle took care of the correct colour.

The ready-made panels.

There is almost no difference in colour between the oak panels and the original oak casing. The gramophone connection is visible between the E424 and the E452T.
Low frequency transformer
Old situation with home-made LF transformer.        The "new" Philips LF transformer.
When finally the valves, a temporary volume control and the Philips 4000 LF transformer arrived, the next step in restoring the radio could be made. The home-made LF transformer was removed and the Philips 4000 transformer was put in its place.
Valves
The new valves and the support bracket for the 506 rectifier.

The original valve set was used: apart from the 506K, the B443 as amplifier, the E415 as detector and the E442 as HF valve. This picture still shows the C443, the E424 and the E452T.
Wanted!
I'm still looking for a volume control with the peculiar small bakelite knob (it is original!) and the aluminium back panel. Who can help?
Finale
What remained after the operation... (together with a few meters of yellow and blue connection wire of course.)
The end...?
I thought that this was the end of the restoration project, but this proved not to be true. The old paper condensers were in a bad state and had to be replaced by new ones. Alas, an original circuit for this radio was not available in readable form so I had to use a clear, but in the end not completely correct circuit that was available on John Hupse's website to replace the old paper condensers by new ones, but unfortunately this resulted in a nasty 100Hz hum. Many emails and consults by Ed Plevier and John Hupse followed, and in the end the problem was found: a fault in the circuit.
The correct circuit is now available on my website and on John Hupse's website. Amazing how a radio, made in 1930, can keep three people busy for a number of days.
The new condensors were connected like this... ...and had to be connected like this  

Many thanks to John Hupse, Philip Apeldoorn, John Hupse, Ed Plevier and Arjan van Schaik for their advise, pictures and components.