I'm restoring a post war, all American five, Fada radio, model 220 ( circa 1948). I replaced the filter
caps, from 30ufd to 22 ufd and the power cord. The radio lights up fine and tunes in stations. However,
the audio distorts when you turn the volume up on most
of the stations. I replaced most of the biasing resistors since they were all greatly off value. I swapped out all the tubes yet no change. I tweeked the coils, still the same. I may replace some of the coupling caps nexts. Should I check anything else to
track down the audio distortion I noticed that the
B + volatge is only 70 volts versus the 90 volts the
schematics shows. The resistance to the field coil and
the speaker coil seems OK and the speaker cone looks good. Any ideas? Thanks, Randall

I would suspect a capacitor failure, in particular the coupling capacitor between the first audio plate and the output tube grid. This would not only cause distortion, but would overdrive the output tube resulting in low B+ voltage. While you are at it, I would suggest replacing all the tubular/paper capacitors as they tend to short over time. If your radio has small, square/mica capacitors in the "front end" stages, they are probably OK and would not need replacing.
:I'm restoring a post war, all American five, Fada radio, model 220 ( circa 1948). I replaced the filter
:caps, from 30ufd to 22 ufd and the power cord. The radio lights up fine and tunes in stations. However,
:the audio distorts when you turn the volume up on most
:of the stations. I replaced most of the biasing resistors since they were all greatly off value. I swapped out all the tubes yet no change. I tweeked the coils, still the same. I may replace some of the coupling caps nexts. Should I check anything else to
:track down the audio distortion I noticed that the
:B + volatge is only 70 volts versus the 90 volts the
:schematics shows. The resistance to the field coil and
:the speaker coil seems OK and the speaker cone looks good. Any ideas? Thanks, Randall

:I would suspect a capacitor failure, in particular the coupling capacitor between the first audio plate and the output tube grid. This would not only cause distortion, but would overdrive the output tube resulting in low B+ voltage. While you are at it, I would suggest replacing all the tubular/paper capacitors as they tend to short over time. If your radio has small, square/mica capacitors in the "front end" stages, they are probably OK and would not need replacing.
::I'm restoring a post war, all American five, Fada radio, model 220 ( circa 1948). I replaced the filter
::caps, from 30ufd to 22 ufd and the power cord. The radio lights up fine and tunes in stations. However,
::the audio distorts when you turn the volume up on most
::of the stations. I replaced most of the biasing resistors since they were all greatly off value. I swapped out all the tubes yet no change. I tweeked the coils, still the same. I may replace some of the coupling caps nexts. Should I check anything else to
::track down the audio distortion I noticed that the
::B + volatge is only 70 volts versus the 90 volts the
::schematics shows. The resistance to the field coil and
::the speaker coil seems OK and the speaker cone looks good. Any ideas? Thanks, Randall

Gordo - thanks for the tip. The cap in question looked
like it was replaced once so I skipped replacing it.
However, finally replacing the coupling cap between the detector tube and the output tube took care of the
problem. Thanks