The tuning eye will have a resistor between pins #2 and #4. This resistor is usually 1 meg and often mounted in the socket. If it's open your tuning eye won't respond. Also a negative AVC voltage is required on pin #3 to close the eye. With a strong signal, aligned radio and good antenna this voltage should be greater than - 10 volts.
Norm
: I recently restored a Grunow console from the 1930"s to working condition. The tuning eye, however does not seem to move with signal strength. I have tested the tube and it tests strong. Any suggestions on what might be wrong?