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Last COBRA 2000GTL question on Frequency Clock Module

Discussion in 'General CB Services Discussion' started by Crambone, May 23, 2020 at 7:53 PM.

  1. Crambone

    Crambone Active Member

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    This is mostly for curiosity as my radio is on frequency. But while recapping the frequency / clock module I see there are 3 adjustments. L501, L502 and CT 501, I'm just curious as to what they adjust. I looked through the service manual and cant find any reference of alignment or anything for the module?


     

  2. nomadradio

    nomadradio Analog Retentive

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    L501 is a tuned circuit that matches the input impedance of IC512, the 35 MHz buffer amp. This beefs up the level of the radio's PLL output to drive one of the counter's two inputs. We probe pin 3 of IC512 to set L501 for a peak

    L502 does the same job for the radio's 7.8 MHz carrier oscillator. TP502 is where you monitor the peak setting of the slug in L502. Radio has to be set to LSB or USB to do this.

    CT501 is to calibrate the reference crystal in the counter to read the frequency accurately.

    73
     
  3. Crambone

    Crambone Active Member

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    Thank you, I’ve always wondered what they were. You sir are an endless encyclopedia of radio knowledge, thanks for sharing your wisdom!

    73
     
    Tokin likes this.

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