Antique Radio Restoration

Restoration RCA Superette R8

The restoration I am about to describe is about a radio from my collection: from time to time, it is nice to undergo some restoration for sheer pleasure and for bringing some old relics back to life, among all those which are laying on the shelves, forced to wait for long due to lack of time.

The radio of this post is the Superette R8 made by the American RCA Victor (Radio Corporation of America), company which certainly needs no introduction, since set several milestones in radio history and holder of patents as the super-heterodyne, frequency modulation, etc. This radio is a wooden table model, vertical-shaped case (tombstone) and gothic-style decorations, to recall the features of the churches (hence the nickname “cathedral radio” was also given to radios of this kind, although more often referred to models with round top).

Thanks to its stateliness, the technical characteristics and refinements, this radio can surely be considered among upper class receivers: indeed, it has all the features of a console radio (in terms of number of tubes, sensibility, output power, weight), but embedded in a table case. In fact, the advertisement of the R7, from which this radio was derived, stated that it was The smallest great radio. Technically, the radio is a super-heterodyne, equipped with 8 tubes, radio frequency amplifier stage, separate oscillator by means of a triode, two intermediate frequency amplifiers (IF = 175 kHz), automatic volume control (AVC, one of the first radios with this device) also with a triode, output stage in class-A by means of pentode UX247 and coupled in input and output with transformers (which contribute to the considerable weight of the set). It is interesting to note that the Superette R8 is using the same chassis of the earlier model R7 (distributed also in Italy by CGE), which wasn’t equipped with the AVC and had a push-pull output stage with two UX245: in order to maintain the same number of tubes, one of the two output tubes was replaced by the UX227 for the AVC, and a single pentode tube was used for the output stage. The filaments of the tubes operate at 2,5 volt, unlike the UX280 (5 volt). The AVC triode has a separate winding due to the tensions that would be happening between cathode and filament if this was in parallel with the other tubes.

Restoration of this set has been particularly easy, it just needed the replacement of the electrolytic capacitors (already replaced in the ’30s), performed in a way that could safeguard the original appearance of the chassis, and this authentic gem of the past could play well again. Moreover, there wasn’t the usual problem of the capacitors to be replaced between the preamplifier stage and the output tube, since in this device a transformer is used for the de-coupling between the two stages. During the restoration and cleaning, I noticed that the transformer has already been replaced in the past, probably already in the ’30s, since the original was screwed with its steel sheets horizontal to the chassis, whereas this one was placed vertically, in a way that it was partially blocking the removal of the chassis from the case: in fact, it was installed in a slightly inclined way, to avoid any interfering with the other parts. I also replaced the volume potentiometer, which wasn’t original, with an “original” spare part coming from a scrapped radio of a friend of mine: I would have considered this replacement superfluous, but this instrument, made by Hammalrund, contains an interesting reduction gear mechanism.

The only liberty I took from the philosophy of preserving the originality as much as possible was the accurate removal of the asbestos stripe from the case next to the output and rectifier tubes, making the radio safe from any future contamination of this dangerous material.

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