Original sex mono-parafeed help

[najo49]

I have a set of original parafeed monos. One amp quit. The 220uf cap with a 390 ohm res. across it became very hot and burned up resistor and cap. This cap gets the green lead from the plate choke then it goes to ground. I have swapped the plate choke with another no change, and also changed the 220 cap and 390 ohm that go to gnd. All voltages are the same as the working one but no sound. I got no ac in the output end of the parafeed 3.3uf cap. which goes to parafeed opt. I have c4s in this amp and I have swapped boards with the working one and no change. Any ideas. Jan Olsen

 

[Doc B]

Check for AC going into the output stage triode grid. Sorry don't recall what pin. Check a 6DN7 pinout online and you should be able to see which grid goes with the plate that is attached to the parafeed capacitor.

 

[Paul Joppa]

That would be pin 1; check the resistance to ground there as well - if a solder joint has come disconnected and the resistance is high, then the power sections will draw excessive current, possibly the cause of the damaged cathode resistor and capacitor.