[gprutchick]

My 38-10 has no shield bases and obviously no shields. I have noticed that the tube sockects for the 6A8, 6K7 and 6Q7 do not have a socket installed a the pin 1 location. I am using metal tubes at these locations. My understanding is that the metal case of these tubes is internallay connected to pin 1.

Q1. Why did Philco use sockets without pin 1? Was it because glass tubes were used? My set was oscillating and motorboating. I temporarily jumpered pin 1 of the IF tube to chassis and no more oscillations.

Q2. Would it be a good idea to replace the tube sockets and connect pin 1 to chassis in lieu of shields? I know this is alot of work but it may be more difficult to find shield bases and shields.

I worked out the values for C7 and C9 and have have rebuilt the compensator. The range for C7 is about 13pf to 50pf and the range for C9 is about 160pf to 450pf. I have done an IF alignment. The IF is very strong (470KHz). I have done the alignment on the broadcast band, not totally happly with it, and the radio does not receive any stations. I have a home made am transmitter that transmits at 1500KHz. My 38-10 receives it but faintly with alot of noise. There is alot of noise across the entire band. The antenna coil resistances seems ok. I also checked it by applying a signal generator to the antenna terminals while monitoring the G4 grid cap with a scope. The signal gets through the antenna coil and resonates at the frequency set by the dial.

I have tried several 6A8 tubes.

I checked the 6A8 oscillator and confirmed the frequency of oscillation with a frequency counter. The frequency is 470KHz higher than the dial setting. Grid voltage varies from -12 to -18V, which I think is good. The frequency of oscillation is approximately 470KHz higher than the dial setting.

What am I missing?
I may put this one asside for a while because frustration has set in.