Fast tuning silent function

      Fast tuning silent function

      Dear Members,

      I need some help to locate in the schematic, the silent function during fast tuning. I am restoring a FB 18 and all the stations can be heard during high speed tuning. The silent function work fine during the few minutes after the radio is powered on. After that, the silent function is lost.

      thanks in advance,

      Dieser Beitrag wurde bereits 2 mal editiert, zuletzt von „Bruno Gandolfo“ ()

      Hello Bruno,

      the voltage for muting the driver triodes (EF86) for both channels during automatic tuning comes via line "F" in the schematic.
      You can adjust the sensitivity with P601. Line "H" leads to the control switch of the automatic tuning where there´s a muting switch for each direction.
      You will have to trace this voltage to find the problem. Especially check contacts and resistors.

      Dieser Beitrag wurde bereits 1 mal editiert, zuletzt von „nightbear“ ()

      Hello Achim,

      It was a lot of work to check all the items on line F and H.
      I have found open the 1M resistor (R718) on ECL80 grid 1, however its replacement does not fix the problem.
      All the voltages where inside normal values.
      The automatic control switches work fine for each direction.
      The P601 potentiometer has no effect on tuning sensitivity. According the alignment instruction it should be adjusted for minimum hum voltage at the output.
      A curious thing is that the muting function, in high speed work fine during few minutes after the radio is powered on. After few minutes the stations can be heared.
      It can be possible than the muting function is lost when some part become warm.
      After to much time invested I remain puzzled.. :) ... I will be very thanked to receive some help...
      best regards,