The cause of the hum became obvious immediately when I removed the back panel. The power supply electrolytic had leaked and dried out. I replaced the electrolytic, the coupling capacitor to the output valve and the electrolytic for the negative bias voltage. And I had to repair the antenna input, using some epoxy cement.
After switching it on, I got a terrible hum. What was wrong? I had fitted a different electrolytic that had a slightly larger screw thread so its case did not make contact with the connection lug. After fixing this, I got complete silence.
There was not even a tiny hum as I touched the gramophone input. This was cured as I replaced the second ECH21. But still no reception. I replaced the other ECH21 and now the radio played. I saw that both ECH21's had cracks around some of their pins. A loss of vacuum may have been the cause, although the getter inside the valves looked good.
After this, the radio played fine and I was really satisfied by its performance. But in 2008, I needed to trade this little old radio to make room for others.
Copyright © 2003 by Onno's E-page published 2003-07-06, last updated 2008-10-04