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Vintage Radio

The Hotpoint Bandmaster J35DE console radio

By Maurie Findlay, MIE Aust, VK2PW

While there were many run-of-the-mill radios produced during the valve era, those with better performance were considerably more expensive and are now hard to come by. And while the sets made by AWA were highly regarded, those branded Hotpoint would these days hardly rate a second glance by vintage radio collectors. However, they would be missing out.

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The Hotpoint Bandmaster J35DE was a 1940s console radio that offered quite good performance in its day. This example is still in good condition, although the grille cloth needs replacing and the cabinet requires work.

Hotpoint-branded radios were made by AWA Pty Ltd (Amalgamated Wireless Australasia), Australia’s biggest electronics company in the 1940s. Which just goes to show that “badge engineering” was not confined to the automotive industry.

The Hotpoint Bandmaster T55DE/J35DE is a 5-valve radio offering AM broadcast band and shortwave reception, with provision for a pick-up to play records. The chassis may also have been the basis for radiograms made by AWA at the time.

The Hotpoint J35DE/T55DE chassis was virtually identical to that in the AWA 721-C console radio and the 618-T mantle (or table) radio. A set of this general type, in good order, will have a reserve of performance for local broadcast stations and will receive the stronger shortwave stations.

With care and patience, the valves and other components can be tested, replaced if necessary and the set re-aligned for best performance using no more than a multimeter. That said, the meter needs to be a modern digital multimeter.

Multi-range meters available at the time the Hotpoint was designed mostly used a moving coil meter which required a current of 1mA for full-scale deflection (FSD). Such a meter would give readings very much in error in many radio circuits because of the high resistances involved.

For example, take a look at the circuit diagram of the radio featured in this article. At valve V3’s plate, it would read about one third of the actual voltage on the 100V scale. That’s because the relatively low impedance of a moving coil multimeter loads down the voltage when attempting to measure such a circuit.

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This view shows the neat arrangement of the major components on the top of the chassis. A label on the dial backing plate shows the drive cord arrangement.

By contrast, a modern digital multimeter has an input resistance of 10MΩ (100 times greater) and would have very little effect on the voltage.

Apart from a good digital multimeter (DMM), you will need spare parts, small hand tools and most important of all, some skill with a soldering iron. Still, if you have assembled a typical PCB, you should have no trouble soldering parts in an old radio chassis. However, you will need a bigger soldering iron to do some of the work.

The Hotpoint T55DE is typical of 5-valve sets made in the valve era. It used good quality components which were operated conservatively and offered what most owners wanted: reliable reception of the local broadcast stations.

More elaborate receivers, for use in remote areas, would have had an extra stage of amplification between the aerial and the mixer stage. For those needing high volume, a more elaborate audio system, perhaps using push-pull valves, would be prescribed. In addition, shortwave reception could be improved by incorporating a bandspread system so that particular frequencies can be tuned more easily, while an extra RF amplifier stage is also a big advantage at the higher frequencies. And so it goes on.

The aim of this article and the one that follows is to give enthusiasts, with only a basic knowledge of radio, a systematic means of restoring vintage receivers to full performance. A particular set has been chosen in order to avoid a string of generalities which could easily have been confusing. I have redrawn the manufacturer’s circuit diagram, with component values marked, to avoid the need to refer to the parts list when studying the diagram.

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