Nancy Von Essen
Feb 25 Expand Messages
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The general rule is as follows:

  tuning range too narrow, increase C and decrease L

  tuning range too wide, decrease C and increase L

Sounds like yours is too wide.

1)  First, you gotta get the high end of the FM band to tune to the dial.  Adjust the trimmer cap so a station comes in properly on the frequency scale.  Write it down.

2)  Then go down to the lower end of the scale and locate a known station.  You will find it reading somewhat low.  Write it down.

3)  Adjust the oscillator coil to decrease its length.  Just by a bit.  Shorter coil has higher L.

     Now repeat steps  1  and  2  until you are accurate at both points.  Try to stay away from the very ends of the band.  Around 106 MHz  and 90 MHz are OK.

    That gets the oscillator calibrated.

    Go back to step one and adjust the other trimmers to maximize signal strength at the high end of the FM band.   Then go to step two and adjust the other coils to maximize signal strength at the low end.  Repeat until any changes required get small.

    Keep notes in case you need to backtrack.

Works for my LT-112B.


Note that the trimmer caps are adjusted at the high end of the band and the coil lengths at the low end of the band  AND  you have to readjust the trimmer cap after you mess with the coil length.  And use a wooden tool to tweak the coil.  If too narrow, make the coil wider in step three. 

You might also check how you are doing at mid band or 98 MHZ.  And use Deoxit to clean the rotor contacts of the tuning cap with a Q-Tip.  Don't spray.


Now if someone could fix the tuning meter movement on my 312 D.


Regards

Ed VE.