Philco 87--Looks pretty, doesn't she? Can't imagine why anyone would hide this beauty inside a wooden cabinet. Anyway, I'm bumping this back to the top for more advice.
I've replaced or rebuilt every questionable component. That includes the filter block, all other paper caps, and bad resistors. The test data looks good with one exception. But so far I have weak reception which can probably be described as good sensitivity and poor selectivity. The weak audio is competing with a loud 60-cycle hum. My next step would be to look for faults in the filter block, but I'm going to seek counsel first.
Here's the data. My figures in red. What stands out to me is that the detector plate is getting a small fraction of the specified voltage.
The hum is steady and unchanged by volume. It does decrease when the AC line voltage is decreased. The hum is unchanged when I pull the detector tube. When either 45 in the 2nd AF is pulled, the hum is reduced equally. The only tube I've changed is the 1AF 26 globe. I only replaced that because the globe went microphonic whenever the set was jiggled.
I've marked up this schematic to keep track of what I was doing. Blue numbers are my measurements, green numbers are new components, and red arrows indicate that I've checked the continuity of coils.
As I said, I'll take apart the filter block next. When the hum is conquered I may have to learn how to neutralize the Neutrodyne. Beyond that, I'd sure appreciate any ideas on what else I should check into.
Thanks much.
- The Eternal Novice