Thanks for your thoughts Tim.

No, there's not means to switch the AVC off. The TR-4 has a scheme whereby
signal is taken off an IF transformer and applied to an "AVC amplifier" that
feeds it
across a plate resistor that develops current which then varies the voltage
to the grids of the
preceding IF amplifiers and detector. As the voltage is varied, the output
from their plates
increases or decreases the gain, depending on whether the signal is stronger
or weaker which provides the AVC control. The S-meter comes off of the same
system. My S-meter will not adjust any lower than "S6" with the S-meter zero
pot, so I am guessing that there is too much current being drawn somewhere
resulting in too much grid bias which provides too much AVC action, which is
the same thing that rotating the RF GAIN control down does.

My problem is that I hear almost no "receiver hiss" even with the volume
control all the way up. I do hear signals, but they are very weak and
rotating the IF and RF transformer trimmers has an effect on the amount of
signal from my sig gen that I get. But the overall volume is way, way down.

In addition, if I inject a 9 MHz signal to the grid of the 1st IF
transformer, I get lots of
signal from the plate. But if I inject a signal to the grid of the 2nd IF
transformer, the signal level from its plate is very low. Ordinarily that
would mean the tube is defective, but it's not. I've swapped two NOS tubes
(that all test well on a reliable professional tube tester).I've checked
that IF amp's bypass caps and load resistors. Nothing.

So my focus is still on the AVC.

By the way, I was mistaken. What I thought was a "22 Meg" resistor is
actually a 2.2 Meg. I thought the 22 meg figure was a little "out there" but
until I compared my copy of the manual with another copy, I discovered the
printing of the
schematic was somewhat blurred causing the decimal point to be unseen. So
finding the "missing
22 Meg resistor" isn't an issue anymore. Unfortunately, as it turns out, the
2.2 Meg resistor was within tolerance. That would have
been just too easy.