Freiburg 3DS - distorted sound

      Hello, recently I aquired Freiburg 3DS. As this is very special radio I thoroughly checked it and replaced all the capacitors, also cleaned the contacts and engines.
      What is troubling me, I can't get rid of distortion. Radio plays with not enough bass as it is, but what's worse if I turn the volume up, the sound becomes distorted.
      I checked with Freiburg WIII - he plays great with loudspeakers from 3DS.
      I even replaced both EL84s with those from W3 and 100 - no change.
      ECC83 is NOS, EABC80 is checked and good.

      The current of both EL84 is slightly low - 74mA to be exact (as calculated on resistor 90 ohms).

      I also checked potentiometers and many of high-ohm resistors, they measure alright.

      I'm starting to worry that there might be a problem with output transformer, as 200 ohms resistor between both of the 50uF capacitors was charred.

      Maybe somebody knows the resistance between the windings?
      In my transformer it's like this:
      Anode 1 - 0
      Grid 1 - 45 ohms
      The middle - 94,8 ohms
      Grid 2 - 180,2 ohms
      Anode 2 - 346 ohms.

      I measured from the plate of EL84 closer to volume engine.

      Best regards,
      Piotr

      I know this is an old thread but I am interested in whether you found the cause of your problem. If not, this is how I would try to narrow down the stage that is causing it. Have you tried connecting an external source of audio such as a CD player. If the problem still exists then that would reduce the area of concern to the audio amplifier section. I would still check ECC83 with a tube tester or try another one. It is a two section tube and sometimes one section goes bad and causes distortion. I would also try good replacemnet output tubes. If the distortion disappears when when using just the audio input then I would be looking at your tubes in previous sections. EABC80 is a prime contender for causing distortion. If you have replacements that you know are good then try them one at a time.

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