[glyphmon]

Okay, so I finally ate enough ice cream and Trader Joe's milk chocolate peanut butter cups to get into a headspace to tackle this.

We still have the under-voltage situation at the Screen Grid (pin 4) on each of the 6A8 and 6K7.  Expected is 100V.  Tested has ranged from 61V to 65V.  R4 has been tested good and substituted with new stock also testing good, resulting in no difference.  Voltages testing as expected from the voltage dividing resistor and on most other pins (small voltages discrepancies to be discussed later, if necessary).

In summary from my previous post:
Testing without an antenna connected at all yielded approximately the same results as before: 175V coming from the R14/R15 junction up to R4; 63V between R4 and the Screen Grid pins (pin 4)
Testing with antenna connected and tuned to my AM transmitter: 187V and 91V respectively

Tonight, with one leg of C15 disconnected, receiving no signal:
Both 6A8 and 6K7 in: 175V and 65V respectively
With 6A8 only removed: 203V and 138V respectively
With 6K7 only removed: 177V and 66V respectively
With both removed: 220V and 219V respectively

So, my amateur brain says this final result with almost no difference across R4 is because there's no load?
And looking at the the result with only 6A8 removed, seems like there's clearly more voltage than just a single tube requires?  Makes sense since there are supposed to be two, but only one is installed.
And looking at the result with only 6K7 removed, it is almost the same as any other test with both tubes in, and C15 in or out.
Now, my amateur brain's conclusion would be that there might me something wrong with the 6A8, since whenever that tube is removed there seems to be an abundance of voltage, but I've also swapped the 6A8 with another non-tested 6A8, but it is from at least a semi-functional radio with no substantial difference.

Anyone care to chime in on what these results imply?
Would it be worth ordering a replacement 6A8 in case both of the ones I have access to may have both failed in the same way?
Does the fact that there's almost no difference in the voltages measured with C15 connected versus disconnected suggest I have a bad new capacitor?
Further diagnostic options?

Best wishes,
Roy