01-02-2018, 01:33 AM
Ron;
I don't know if anything is actually wrong with the FM-100-C ratio detector transformer other then it is not compatible with the surrounding circuitry, so I would not be in too big of a hurry to toss it, maybe save it as a spare for an FM-100-C. I can only go by the sections of each schematic that you posted but there appears to be a substantial difference in the ratio detector circuitry in each tuner, such in the way the cathode of the 6AU6 tube is connected, one shows the cathode connected to ground, in the other there is an RF choke, and a 5000 mmf cap, and a 1 meg resistor connected to it. Also the screen and plate voltages are different. RF circuits are like black magic to me, FM even more so, so when all else fails I go back to factory specs.
Regards
Arran
I don't know if anything is actually wrong with the FM-100-C ratio detector transformer other then it is not compatible with the surrounding circuitry, so I would not be in too big of a hurry to toss it, maybe save it as a spare for an FM-100-C. I can only go by the sections of each schematic that you posted but there appears to be a substantial difference in the ratio detector circuitry in each tuner, such in the way the cathode of the 6AU6 tube is connected, one shows the cathode connected to ground, in the other there is an RF choke, and a 5000 mmf cap, and a 1 meg resistor connected to it. Also the screen and plate voltages are different. RF circuits are like black magic to me, FM even more so, so when all else fails I go back to factory specs.
Regards
Arran
![[-]](https://philcoradio.com/phorum/images/bootbb/collapse.png "[-]")
