[Hallicrafters] SX-28 S-meter adjustment

[Julian Bunn]

I adjust my S-meter according to the instructions: disconnect the 
antenna, turn on the AVC,
and adjust the needle for a 0 reading (leftmost). No problem.

Now when I attach an antenna, turn AVC off, and tune in a strong signal, 
the S meter needle
barely moves (but it does move).

If I turn on AVC, the needle swings hard to the right.

(I have back to back diodes across the meter terminals, and I have 
replaced the 27k 2W
meter resistor: the old one was way too high ... about 40k).

What might the problem be here?

Thanks!
Julian