04-19-2019, 12:10 AM
The 45C and 71B use different tone control parts. According to the service bulletins Model 45 uses part 30-4178 and Model 71 uses part 04757.
We have the specs for some tone controls in the Philco Library (come from various Philco parts catalogs):
https://philcoradio.com/library/index.ph...-controls/
According to that the 04757 tone control is two-position - either open (0uF) or connected (0.02uF). FWIW that matches what is shown on the schematic.
Since the 71B in question has a three position tone control perhaps there was a change to a different part along the line? Especially likely since yours is the later version (code 125?) with the shadow meter - the service bulletin probably doesn't cover it.
Perhaps it uses the same tone control as in the Model 91 (pure speculation) - but that was a four-position job like you describe, part 04787: 0 / 0.015uF / 0.025uF / 0.035uF.
We have the specs for some tone controls in the Philco Library (come from various Philco parts catalogs):
https://philcoradio.com/library/index.ph...-controls/
According to that the 04757 tone control is two-position - either open (0uF) or connected (0.02uF). FWIW that matches what is shown on the schematic.
Since the 71B in question has a three position tone control perhaps there was a change to a different part along the line? Especially likely since yours is the later version (code 125?) with the shadow meter - the service bulletin probably doesn't cover it.
Perhaps it uses the same tone control as in the Model 91 (pure speculation) - but that was a four-position job like you describe, part 04787: 0 / 0.015uF / 0.025uF / 0.035uF.
![[-]](https://philcoradio.com/phorum/images/bootbb/collapse.png "[-]")
