10-18-2020, 11:01 AM
Little update plus questions. Completed replacement of paper caps. While checking for shorted caps before replacement found one that was shorted. Now the secondary center tapped windings that are high voltage to the rectifier plates is in the normal range for this transformer of 265 volts on either side of the center tap. Decided I would delay increasing resistor values to lower this voltage till I have solved other issues, leaving radio plugged into dim bulb tester and variac.
Secondary winding for 5 volts indicating 5.65 volts. Think I'm happy with this for now.
This radio is the first in my limited experience with tube type radios to have capacitors in 6 of the nine tubes, heater circuits. Secondary winding providing 6.3 volts to the heater circuits, was producing only 3.5 volts. Seems all six capacitors for these 6 tubes shorted to ground. Just clipped one lead on each of the 6 caps and now indicate 5volts on the heater winding instead of 3.5 volts but still low. Now 7 of the 9 tubes exhibit a normal looking glow, two are still dark.
This is also my first tube type radio to have the 12AT7 fm osc converter, 6AU6 fm rf amp, 6BE6 am osc converter, with all associated components enclosed within it's own removable metal cage. Now for my questions.
1. Are the small capacitors in each of the 6 tubes heater circuits and the metal cage to minimize hum or interference in the final stages?
Three of the small capacitors in the heater circuit are of the circular flat mica type. Three are of ceramic tubular type. The three ceramic caps are in the heater circuits of the 6BE6, 6AU6, and 12AT7 tubes which are all enclosed under the removable sheet metal cage.
2. Why were circular flat mica caps used on the three tubes outside the sheet metal cage, and ceramic tubular type used on the heater circuit on the tubes enclosed within the sheet metal cage
3. What would be my best choice in the replacement of these caps?
I have tried researching my questions but failed any progress.
Speaker still silent.
Thanks
Tim
Secondary winding for 5 volts indicating 5.65 volts. Think I'm happy with this for now.
This radio is the first in my limited experience with tube type radios to have capacitors in 6 of the nine tubes, heater circuits. Secondary winding providing 6.3 volts to the heater circuits, was producing only 3.5 volts. Seems all six capacitors for these 6 tubes shorted to ground. Just clipped one lead on each of the 6 caps and now indicate 5volts on the heater winding instead of 3.5 volts but still low. Now 7 of the 9 tubes exhibit a normal looking glow, two are still dark.
This is also my first tube type radio to have the 12AT7 fm osc converter, 6AU6 fm rf amp, 6BE6 am osc converter, with all associated components enclosed within it's own removable metal cage. Now for my questions.
1. Are the small capacitors in each of the 6 tubes heater circuits and the metal cage to minimize hum or interference in the final stages?
Three of the small capacitors in the heater circuit are of the circular flat mica type. Three are of ceramic tubular type. The three ceramic caps are in the heater circuits of the 6BE6, 6AU6, and 12AT7 tubes which are all enclosed under the removable sheet metal cage.
2. Why were circular flat mica caps used on the three tubes outside the sheet metal cage, and ceramic tubular type used on the heater circuit on the tubes enclosed within the sheet metal cage
3. What would be my best choice in the replacement of these caps?
I have tried researching my questions but failed any progress.
Speaker still silent.
Thanks
Tim
