38-4 or 38-5 Tone Switch Functions - Printable Version
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+--- Thread: 38-4 or 38-5 Tone Switch Functions (/showthread.php?tid=18521)
38-4 or 38-5 Tone Switch Functions - davemc - 06-07-2018
http://www.nostalgiaair.org/pagesbymodel/252/M0013252.pdf
I would like to know what the 2nd position of the tone switch on a Philco 38-4 or 38-5 is supposed to do. Position 1 is OFF. Position 2 appears to short the volume control tap to ground through a 40K (32K in my radio) resistor. That just lowers the volume in my radio - no apparent affect on the tone. In my radio, the 3rd position appears to be "hi fi", and the 4th and 5th position reduce the treble by various amounts.
RE: 38-4 or 38-5 Tone Switch Functions - LarryFS - 06-07-2018
I have a 38-3 which has the same four point tone control as the 38-4 and 38-5 according to the 1938 Philco sales catalog (see http://philcoradio.com/phorum/showthread.php?tid=15785). Position 2 of the switch is "brilliant" for speech; position 3 is "bright" for normal reception of music; position 4 is "mellow" for the first noise-reducing stage; position 5 is "deep" for noise-reducing for distant reception. I hear very little difference between positions 2 and 3 on mine. I can't comment on how each of the 4 tone circuits functions based on the schematic.
Larry
RE: 38-4 or 38-5 Tone Switch Functions - Electrothaumaturgist - 06-07-2018
Have you guys ever cranked up your sets , way past the bass sector to the point of great loudness and then played with the selector switch between those "non working" settings? (Be careful to keep it out of the deep bass positions during this test, or you might be sorry). I'm willing to bet those work just fine. If they don't, you may have to go in and change out some resistors you may have missed. If I'm not mistaken, my 38-1 has the same switch, and it works 100%, though there is a slight change in tone between positions 2 and 3 when the volume is low, it is very noticeable at higher volume levels.
RE: 38-4 or 38-5 Tone Switch Functions - LarryFS - 06-07-2018
The 38-3 I have actually belongs to a friend of mine so I haven't cranked it up. I can tell a difference between positions 3 and 4 and 4 and 5 at normal volume level so I figure it's working. I did replace resistors that were out of tolerance.