[MrFixr55]

Hi Bridkarl,

+1 on the others. C39, the cap across the output transformer primary is to cut high frequency oscillation and tailor high frequency response and is in almost all output stages. C40 is to capacitively couple the output tube plate to high impedance "can" type headphones. Do not use a modern pair of headphones with this unit.

Still having the motorboating problem? I don't know if you saw my previous post. The 6F5 1st audio amp has a grid cap. Make sure that this wire is either shielded or very close to the shield. If this a metal tube, make sure that there is continuity between the metal case of the tube and chassis ground.

Try unplugging the 6H6 detector tube then powering back up and turning up the volume control. You may hear some hum but should not hear motorboating. Pulling the detector tube divides the radio into 2 sections: the amp and power supply, and the RF / IF section. This is an example of "divide and conquer" troubleshooting. If the motorboating continues with the detector unplugged, then troubleshoot the amp and power supply. If the motorboating stopped, power down, reinstall the detector, pull the IF tube and retest. If no motorboating, reinstall the IF tube and pull the mixer and oscillator tubes. Continue in this manner until the offending stage is discovered and troubleshoot that stage.