07-18-2022, 10:08 PM
Hi George,
The plot thickens. The good news is that your "Autodyne" 1st Detector appears to be working unless the output of your signal generator is sufficient to blast through. If you set the generator to 1400KHz and tune above and below 1400 KHZ and the signal fades, that is a good sign. If you have another radio, place it near the 91, set its tuner to 1000 KHZ. If that radio starts squealing as you tune the Philco between 700 and 800 KHz, then the Philco's oscillator is definitely working.
A nice divide and conquer procedure is to connect a long wire antenna directly to the 1st Detector grid and if you can tune stations, then you merely need to troubleshoot the RF Section. Disconnect the long wire from the 1st Detector Grid cap and connect to the RF grid Cap. If the stations are received even louder than when the Long Wire was connected to the 1st Det grid cap, then troubleshot the antenna circuit.
Voltage-wise, the 1st Detector voltages compare fairly well to those listed in the Schematic. a 10 - 15 or even 20 % difference in plate and screen voltages is not USUALLY fatal. The RF Section is a bit of a puzzler. Both the RF and IF Amp Tubes are '44s and share the same cathode resistor and bypass condenser. I don't know why the cathode voltage would be as high as the schematic states that it should be for the RF tube when it is much lower on the IF Amp tube and both cathodes connect to the same resistor and bypass capacitor. Schematic calls for 25V for RF Amp cathode, but 5V for the IF Tube cathode. Also don't understand why the screen voltage for the RF amp is listed as 50V when the screens for the RF, 1st Detector and IF Tube are fed by the same resistor and bypass capacitor. The only difference resides in the fact that the readings are listed as to cathode and the RF cathode reading is low, but circle back to the beginning of this paragraph and scratch your head like I am.
Best Regards and good luck.
The plot thickens. The good news is that your "Autodyne" 1st Detector appears to be working unless the output of your signal generator is sufficient to blast through. If you set the generator to 1400KHz and tune above and below 1400 KHZ and the signal fades, that is a good sign. If you have another radio, place it near the 91, set its tuner to 1000 KHZ. If that radio starts squealing as you tune the Philco between 700 and 800 KHz, then the Philco's oscillator is definitely working.
A nice divide and conquer procedure is to connect a long wire antenna directly to the 1st Detector grid and if you can tune stations, then you merely need to troubleshoot the RF Section. Disconnect the long wire from the 1st Detector Grid cap and connect to the RF grid Cap. If the stations are received even louder than when the Long Wire was connected to the 1st Det grid cap, then troubleshot the antenna circuit.
Voltage-wise, the 1st Detector voltages compare fairly well to those listed in the Schematic. a 10 - 15 or even 20 % difference in plate and screen voltages is not USUALLY fatal. The RF Section is a bit of a puzzler. Both the RF and IF Amp Tubes are '44s and share the same cathode resistor and bypass condenser. I don't know why the cathode voltage would be as high as the schematic states that it should be for the RF tube when it is much lower on the IF Amp tube and both cathodes connect to the same resistor and bypass capacitor. Schematic calls for 25V for RF Amp cathode, but 5V for the IF Tube cathode. Also don't understand why the screen voltage for the RF amp is listed as 50V when the screens for the RF, 1st Detector and IF Tube are fed by the same resistor and bypass capacitor. The only difference resides in the fact that the readings are listed as to cathode and the RF cathode reading is low, but circle back to the beginning of this paragraph and scratch your head like I am.
Best Regards and good luck.
"Do Justly, love Mercy and walk humbly with your God"- Micah 6:8
Best Regards,
MrFixr55
