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RCA 6K3 Preliminary Capacitor/Resistor Research
#33

Hi Glyphmon,

+1 on Morzh's comments. Most caps are either for filtering the output of the rectifier (the electrolytics and C32), Audio stage coupling (C27, C24), Tone control (C25, C26)parasitic oscillation suppression (C29 across the output transformer primary), Decoupling (C15), tank circuits, etc. If C27 shorts or leaks, this can cause the output tube or output transformer to burn up due to excess current. A shorted C29 will bypass the output transformer. I strongly recommend that these caps be replaced, as they are almost 90 years old and do leak, short, etc. The various trimmers and mica caps generally don't require replacement.

After replacing the rest of the caps indicated above, ohm the output transformer primary (between the screen and plate of the 6F6 (Pins 3 and 4).

One "divide and conquer" spot is the Phono input on the back of the radio. For radio, the link should be between 1 (output of the detector) and 2 (input of the amplifier). By opening that link and connecting an audio source between pin 2 (audio in) and pin 3 (chassis ground), you can verify that the amp works. If the audio inputted through the phono input is not heard through the speaker, then troubleshoot the audio and power spply circuits. If Audio is heard, then jumper pins 1 and 2 together and troubleshoot the "radio" section of the radio (Oscillator Mixer, IF and detector).

One possible (or probable?) failure is the "Voltage Divider Resistor", R14-R18. If this resistor opens, especially if R14 or R15 opens, cathodes of all tubes other than the rectifier and detector will not be at their correct potential, will float to B+ level and there will be no sound. If R16, 17 0r 18 opens, B+ or screen voltages will be lost. If you replaced them, good. That is where you want to start, when verifying voltages, in case of a cold joint or miswire.

"Do Justly, love Mercy and walk humbly with your God"- Micah 6:8
"Let us begin to do good"- St. Francis

Best Regards, 

MrFixr55


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RE: RCA 6K3 Preliminary Capacitor/Resistor Research - by MrFixr55 - 05-10-2026, 12:50 AM



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