This radio was given to me along with two others. It's owner was clearing out his garage and needed someone to take it away.

These radios were first sold in May 1950 at a price of just over £15.

It looked like it hadn't been used in a very long time, there was a lot (50 years worth by the look of it) of dust and spiders webs inside the case.

It looked promising, all the valves were all original and there didn't seem to have been any previous repairs, also none of the screws were missing from the case.

The drive cord for the tuning capacitor was snapped and the old rubber power cable lead had completely fallen apart, just touching the cable made it crumble.

Click here to see the circuit diagram

After carefully sucking out the dust and spiders webs with a vacuum cleaner, I took out all the valves except the rectifier. I replaced C25 which is the coupling capacitor feeding the grid of the audio output valve (it measured OK, but these capacitors can damage a lot of components if they decide to conduct DC). All the other wax/paper capacitors measured OK, so I slowly brought up the HT (using a variac and resistor in series with smoothing capacitor). The HT came up OK and the heater voltages were fine, suitable encouraged by this I put the rest of the valves back into the set.

The audio output valve started sparking internally when the HT came back up, so I quickly removed it and checked the voltages at it's socket. They all seemed OK, so I figured there must be an internal fault in the valve. I took the output valve out and tried putting the scope onto the wiper of the tone control (R14) and saw a nice flat trace (instead of audio or noise). At this stage I took all the valves out and put them through my valve tester.

One by one each of the valves showed up faulty. I carefully checked them again and got the same results. The rectifier valve was the only one that even half worked, the output valve showed up as having serious internal problems and the other 3 had very very low gain.

My valve tester is quite old (as you can see above) and I didn't want to believe that all the valves were all faulty, so I got the valves tested on another tester and the same depressing results were produced.

I'm not sure what happened to the old valves. They all appeared to have retained their vacuum and all drew the correct filament current. Perhaps they were sitting too long without being used. I have heard the term "Cathode poisoning", but no-one has been able to explain it to me yet.

I sent to England for 5 new valves and while I was waiting for them to arrive I rewound the broken drive cord. When the new valves were installed the radio worked first time.

CLICK HERE TO HEAR THE RADIO WORKING ! 

Rear view

Don't forget that there are lethal high voltages in old valve equipment, don't even take the back off an old radio if you don't know how to deal with these. Do as much work as possible with the power OFF. If you have to make adjustments or take readings with power applied, be VERY careful. Use insulated tools and only use one hand (so if you do touch something you may avoid putting yourself in the unfortunate position where electrical current flows from one hand to another, though your heart). Beware capacitors that hold high voltage charges even when equipment is disconnected from the mains.

On a more positive note, valve radios aren't hard to fix and they make nice useable "furniture" for your home. They will still work after a nuclear bomb goes off near your house (solid state equipment is damaged by the huge electromagnetic pulse). Someday they might be worth a lot of money, so the more old radios you have the richer you'll be (I'll be a millionaire !)