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RE: Fisher 500C Tuning Strength Meter

Posted by Uncle Mike on March 22, 2017 at 05:27:38

In Reply to: Fisher 500C Tuning Strength Meter posted by jaynemo on March 21, 2017 at 10:16:51:

Plagiarized from Seta1 on another forum but it answers your question and gives an idea of what to look for:
"Check the 6AU6 in the V6 position for the last IF stage. The grid circuit here has a resistor (47K I believe ) and then the meter with a resistor capacitor shunt across it. The meter does not have to work for the tuner to work. But if the tuner is badly out of alignment, especially this stage, you will not get sufficient grid current to cause the meter to deflect. If this tube ever develops a grid short, it can take out the meter. If the transformer is bad, the tuner just won't work and the meter will either be at 0 or fully deflected depending on how the transformer dies. Check pin 1 of V6 to see if the voltage varies as you tune in stations. If it does not, chances are your tuner is out of alignment. If it does and your meter still does nothing, check the resistors in that circuit and if they check fine, your meter is probably dead. This circuit seems simple, but it depends on the rest of the tuner working correctly and up to spec.
As for the FM stereo issues, first off, if your tuner section is out of alignment, you will never get the multiplex to function properly. If your relay is always in the stereo position, or does not switch on and off properly, check C85, 101, and 107. Also, check your 6GK5 (V7) and replace it if it is weak. Also check the 1 meg resistors in the grid circuit of V101 in the multiplex circuit.
I have run into several bad ratio detector transformers in these receivers.
The transformers are either open, or the tuning slug can not be moved. In either case, it will need to be replaced. This thing must be adjusted correctly or the receiver will sound distorted on FM and will not work in stereo."

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