05-12-2020, 12:32 PM
Hi Terry,
We are both circling the same questions, I've checked them all once already but I'll do it again to see if there is something I have missed. You say that the HV side of coil 28, pins 3 and 4, are the feedback circuit. Thanks, but is that coil or winding simply a choke? Or has it been tuned to a specific frequency necessary to make that circuit oscillate? Why doesn't that extra resistor across that coil also provide feedback for the plate? If I unhook that coil but leave the resistor in place I lose my B+. I am going to check that again too. That winding measures about 1 ohm. The broadcast oscillator coil, #26, measures about 6 ohms.
I assume the main tuning cap on the oscillator side is working, because during the test you had me perform where I used my SG as an oscillator, I was able to rock on and off the station by moving it. I'll make a specific test to capture the specifications. I have an accurate, dedicated capacitor checker. I've used it to measure the capacitance of that main capacitor already. I'll do it again and share the results.
Also, I have used clip leads to jump around the various contacts on the selector switch to be certain that they are all working. I have cleaned that switch.
I'm waiting on parts. I have ordered all new mica caps for the 100 Pf as well as the other two 250 Pf caps, #6, #14, #32. All of them are out more than 20%. As I already mentioned I have also ordered 2 adjustable oscillator coils.
Tom
We are both circling the same questions, I've checked them all once already but I'll do it again to see if there is something I have missed. You say that the HV side of coil 28, pins 3 and 4, are the feedback circuit. Thanks, but is that coil or winding simply a choke? Or has it been tuned to a specific frequency necessary to make that circuit oscillate? Why doesn't that extra resistor across that coil also provide feedback for the plate? If I unhook that coil but leave the resistor in place I lose my B+. I am going to check that again too. That winding measures about 1 ohm. The broadcast oscillator coil, #26, measures about 6 ohms.
I assume the main tuning cap on the oscillator side is working, because during the test you had me perform where I used my SG as an oscillator, I was able to rock on and off the station by moving it. I'll make a specific test to capture the specifications. I have an accurate, dedicated capacitor checker. I've used it to measure the capacitance of that main capacitor already. I'll do it again and share the results.
Also, I have used clip leads to jump around the various contacts on the selector switch to be certain that they are all working. I have cleaned that switch.
I'm waiting on parts. I have ordered all new mica caps for the 100 Pf as well as the other two 250 Pf caps, #6, #14, #32. All of them are out more than 20%. As I already mentioned I have also ordered 2 adjustable oscillator coils.
Tom
