Antique Radio Restoration

Radio Phonola 563 Castiglioni Restoration

In this post I describe the restoration of a Phonola 563 radio.
For our non-Italian readers, this is one of the most famous examples of Italian industrial design, as it shares the design with the earlier model 547. This model was designed by some of the best known architects of the 19th century: Luigi Caccia Dominioni, Livio e Pier Giacomo Castiglioni. For this reason, radio collectors often refer to Phonola 547 and 563 with the nickname “Phonola Castiglioni“. These radios are often found in many design books and museums of design and modern arts.

Radio Phonola 563 "Castiglioni"

The radio of this article was rather tampered, both mechanically and electrically. In its long life, the radio has been repainted, but someone also decided to strip the paint off leaving several scratches and marks on the bakelite case. One of the push buttons (for the selection of the pre-tuned stations) was missing, as well as the tuning dial (replaced by painted cardboard), the dial pointer, the celluloid cover of the dial.

Conditions of the internal part were far worse. For instance, the support for the loudspeaker and the power transformer was missing, and the transformer was able to move almost freely in the case. Original loudspeaker was not original, replaced by a part from an American radio, what’s more nearly without its cone. This was loose as well: most likely, the original loudspeaker was out of order and some repairer found a spare part with a similar diameter and same speaker impedance, but with slightly different overall dimensions, so that he was forced to remove the prop holding the old speaker up, leaving both speaker and transformer without their support.
I have rebuilt a new aluminium support to which I could fix the transformer and, once reparation is completed, the speaker. As a replacement for the non-original speaker in poor conditions, I installed a speaker with same diameter from another radio.

Moreover, another former repairer, obviously frightened of the complexity of the circuit, came to the idea of simplifying everything removing several capacitors and resistors which were situated in the area between the sockets of the four octal tubes. Following the schematic diagram, I was able to rebuild the circuit that has been tampered with, using new reliable parts. On top of it, someone removed also the two inductors in a series circuit with the power supply, which allowed the radio to work without an external antenna, using the one side of the mains as source of the signal: most likely one of the capacitors connected to the live mains suffered an electrical short, which literally made the two coils to go up in smoke.

The tuning dial cord string also needed replacement. This radio was rather compact for its age, which meant more complexity. Replacing the cord took at least two hours and a half of swearing šŸ™‚

The wave band selector switch was missing the small ball which allows triggering, and was not aligned with the push buttons – this was however quite an easy fix.

After the circuit was rebuilt, I tried to power up the radio – of course, nothing happened. I cleaned the power switch which was malfunctioning and attempted again: only three tubes out of five lit. Tube tester’s response showed a failure of the two tubes, which had open filaments. Once the tubes were replaced, the radio started humming and, injecting an audio-frequency signal in the audio output circuit, the signal came out through loud and clear, so the work previously done was correct and I had to shift my attention farther upstream. Unfortunately the radio part was still silent, and here started a laborious process of diagnose so many faults that it really seemed a Sisyphus’ work. The four intermediate frequency transformers were all completely out of alignment due to the failure of the Mica capacitors, common problem of any Phonola tube radio of this age.
I’ve connected new capacitors in parallel with the out of order ones, and after repairing and aligning the IF stage at 470 kHz with a lot of efforts, radio was still not working, although it was receiving some noises, which meant that much has been done (at least I thought so…).

Then I took a capacitance meter and tested all the Mica capacitors in the radio frequency stage: one was out of order. After its replacement, the radio:
– could receive shortwaves very well but with low volume, and
– could receive standard broadcast strongly but with feedback squealing and howling between the various stations.
Regarding SW bands, the problem was due to an open circuit in the aerial coil, probably caused by a short between aerial and mains. Once repaired, the radio started to receive shortwave bands very well.

Fixing the reception of standard broadcast wasn’t as easy as for shortwave bands. I verified, with the voltage table, that they were in order, so that the reason of the squealing noise was one of the Mica capacitors of the oscillator, that I had replaced previously but, following the schematic of the similar Phonola 547 (I could not find the schematic for the 563), with one with a different value. After a further check, voltages, alignment and everything else were finally in order, radio was finally working perfectly… until one of the ill-famed Phonola intermediate frequency transformers, even if after my controls and alignment, went again out of order: one of Mica capacitors decided to change capacitance without an apparent reason, causing the tuned circuit to go out of resonant frequency.

Verified once more the complete and reliable operation of the radio, I fixed the speaker to the rebuilt aluminium support.

Accurate reproductions were made for the missing push buttons, the dial and the cover of the dial. Should anyone need it, I attach a scan of the reproduction tuning dial. The dial pointer has been redone with a stiff copper wire which I painted black.

This is the final result:

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