A couple of years ago I bought a 1950's Pye valve radio at a local radio rally. It was supposed to be in working order, but I soon discovered that this was not true. Anyway, I thought it would be good experience to get this old radio running again and perhaps learn a thing or two about valves. I'm not old enough to have worked on this sort of gear when it was new !

Click on the small pictures below to display a more detailed picture.

I managed to obtain a circuit diagram of this receiver. My receiver was made in Dublin, Ireland and it seems to be a bit different from the one in the diagram, which is the English one. The big difference is that mine doesn't have an inbuilt frame antenna, it only has provision for an external wire. Maybe radio signals were stronger in England in the 50's ? These radios were first made in 1953 and the original price was £15 2s 1d + purchase tax, I dread to think what that would be in today's money.

As I knew that the electrolytic capacitors (or condensers, as they were called in those days) were original and nearly 50 years old, they were all replaced. Part of the mains cable had been repaired with an elastoplast! , so I changed the cable as well.

After checking for short circuits and obvious faults, I then applied power to the set.

The tuning scale lit up and the heaters in the valves all glowed a dull red, but no sound. Some further checks found a resistor had been changed to an incorrect value (R17) by a previous owner and the audio output transformer had an open circuit primary winding.

The transformer fault seemed to have been caused by C20, which was faulty and passed a DC voltage to the grid of V5. V5 then drew too much current through the transformer and burnt out the primary windings.

The red parts show the faulty components.

After replacing C20 and R17, I checked with the scope and could see an audio signal at the grid of V4. Still no sound as I didn't have a new output transformer. I connected a solid state amp to the grid of V4 (EL41 output valve), (coupled with a capacitor) and found that the rest of the radio was indeed working. I was able to hear stations on Long, Medium and Short wave. Suitably encouraged by this, I got a new output transformer (a modern equivalent). When this was fitted, I was rewarded with a good level of audio from the speaker.

The radio stayed in this condition for about 18 months and got a couple of hours use each week. I always had a suspicion that one or more of the valves were a bit 'tired' as I needed to have a long aerial connected to get good signals and there seemed to be some minor distortion when listening to music. A neighbour of mine GI4VIV (Peter) has an old AVO valve tester and he kindly offered to test the valves for me. It turned out that V1 (ECH 42 frequency changer) was borderline and V3 (EBC 41 detector and AF amp) was well below spec. Peter found a couple of replacements in his junk box and I fitted them one at a time to see what difference they made.

Replacing V3 made a huge difference to the audio quality, with the distortion completely disappearing. I even put the old valve back in, just to hear the difference again.

Replacing V1 made a big difference to the sensitivity, with signals being received even with no aerial connected!

I often use this radio to listen to the "Ham radio today" program broadcast from HCJB in Quito, Ecuador. With 10 feet of copper wire as an indoor antenna I can get quite good reception (Quito is 5,500 miles from here).

Click here to hear the radio working.

Looking back at this restoration with the benefit of hindsight, I've had a couple of thoughts. It would have been easier (and cheaper) to reform the electrolytic capacitors rather than replace them. Instead of taking the valves out to have them tested, I could have measured the DC voltages around the valves and done some sums to figure out which valves were below spec.

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 !)