Telefunken Operette 8
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Disclaimer - if you are following along, you are doing so at your own risk. These radios have potentially lethal voltages that can kill you. If you have not already read my blog on making your workplace safe, head over there first and check it out.
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Apart from it being dusty, as one would expect from having stood for quite some time in a cellar, the radio appeared in good working condition with all mechanical parts intact and speaker in good visible condition. No mouse droppings were found, so that was a big bonus.
I couldn't wait to pull the chassis and take a look at the under side.
I was absolutely amazed to see that the radio was in original condition and no one had worked on it from new. So I set about following back all my connections beginning at the transformer and working my way back through the finals, the AM detector, 2nd IF Amp, Mixer, Oscillator and Antenna pre-amp in that order.
At this point, I wish to thank the Radio Museum for the schematic. Consider joining as a patron it is well worth the membership which starts at a super low price.
As you can see, I have marked questionable capacitors in red. These are either Paper or Wax caps and have served their purpose long ago. The first to be replaced was C44, a 0,01uF 500V cap bringing audio from the EABC80's anode to the grid of the EL84. This was showing a 1 MΩ DC resistance. Any DC bleeding across this cap would over drive the EL84 causing it to heat up and pop. A suitable replacement was found and the cap replaced.
After swapping all the old caps and the tubes, the radio came back to life.
These were the components that were swapped out.
