[morzh]

350 Ohms is better than 500.

I am not sure how -16V develops.


Let's see.
Your three last K's voltage (like the detector, audio and output) are around 2V, which it is (you said in the beginning it was some 2.3V or so). 1.5V is even lower.

Now,, most current flows through this Candohm.

Let's say that 6A8 and 6K7 conduct 14mA together. That will make 125/27 Ohm junction sit at 1.75V (close'nuff).
Then this dictates the last three K's voltage (which is what you have, you said 1.5V or so).
Then (skip the diode, it barely conducts), the 6F5 and 6F6 together conduct 35mA together. Add to that the 14mA, getting 49mA total.
This will make the 27/350 ohms sit at +16V over the centertap, which with the minus sign and the -1.75 added to it will be -18.5V, which is close enough to what it was or what it is now.

And this is what the 6F6 grid is sitting at, -18 or so Volts.

PS. My currents are from the datasheet - they may be a bit different in your specific case.