This cute little set was given to me to restore for a friend, it’s a 5 valve superheterodyne and is mains powered. It is literally the most compact mains valve set I’ve ever seen and very light too. As I understand it, this kind of set would have seen used in the bedside table.
There were many variations of this set over the years, it first came out just before the war and finished in the early 1950s. The tricky thing was determining which variation it was.
As it turned out, it was a ‘Model 3’ which uses a step down transformer to power the valve heaters and a direct connection to the mains to get the HT supply. There’s a half wave rectifier with a pair of electrolytic capacitors and a smoothing resistor making up the power supply.
The usual steps of replacing the wax capacitors for axial polyester and checking the resistors was carried out. I was quite surprised at the number of resistors that were bad, and just replaced them with modern 1/4 watt equivalents.
I found a nice vintage style twisted mains flex on eBay and used it to rewire the power supply. I also re-wired the on-off switch to control the Live line from the mains as in it’s original form, it was switching Neutral! This was a little bit concerning as the chassis would be floating at 240 volt mains potential while the unit is turned off! The new arrangement is far safer.
The chassis was quite rusty too, so I treated it with a rust stopper and eventually decided to mask off the electronics areas and blow over the whole thing with a few coats of black cellulose paint.
The performance from the set is quite good, it’s speaker cone hadn’t really weathered the years well and has adding quite a lot of mechanical distortion. Some time was spent adjusting the supporting structures of the voice coil and some glue repairs of the outer cone support.
The video above shows this radio in action