12-01-2013, 06:31 PM
I agree with Terry regarding returning the 78 tube. The 6D6, while electrically similar to the 78, does not have an internal shield surrounding the plate and must be used with an external shield. Without one the 6D6 can cause regeneration and instability.
It looks like the two 1 Meg resistors and mica cap were used to provide delayed AVC to the IF and converter tubes by using one of the diodes of the 75 tube. This was standard practice on some Philcos and might be a factory mod. It looks like one 1 Meg connects to the cathode and the other to the AVC line. The common ends connect to the diode plate and the mica cap which feeds the IF signal from the coil. I would tend to leaving it as is, since the resistors and cap look factory original.
It looks like the two 1 Meg resistors and mica cap were used to provide delayed AVC to the IF and converter tubes by using one of the diodes of the 75 tube. This was standard practice on some Philcos and might be a factory mod. It looks like one 1 Meg connects to the cathode and the other to the AVC line. The common ends connect to the diode plate and the mica cap which feeds the IF signal from the coil. I would tend to leaving it as is, since the resistors and cap look factory original.
![[-]](https://philcoradio.com/phorum/images/bootbb/collapse.png "[-]")
