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Using an Oscilloscope to measure Frequency on a dual gate Mosfet Mixer?

Discussion in 'General Electronics Discussion' started by Wiradioop, Sep 30, 2014.

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  1. Wiradioop

    Wiradioop

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    Sep 4, 2014
    I am trying to repair a vintage Citizen Band radio. I think the problem is in the synthesizer circuit. Can I check various points like at the gates of the mosfets to verify the frequencies? Or will this load the circuit and stop the oscillating circuits?
    This is a Pace 1000m or 1000b radio 23 channel SSB if anyone is interested in the schematic along with the service manual I will link it. I received the radio non-working. It does receive static only and has no TX. Guess if I could find one working to look at that would be a great help. The nice thing is I have the service manual and the schematic, so it should be repairable.
    http://www.cbtricks.com/radios/pace/cb1000b/index.htm
    Not sure how much help I can get here but it is worth a try. I've already done a re-cap and a lot of poking around in this thing. I'm not sure what I'm up against. It maybe more than I can handle.
    Thank you

    JC
     
  2. Wiradioop

    Wiradioop

    5
    0
    Sep 4, 2014
    I am hoping that someone is interested in this forum. If you look at the Figure 2-1 Synthesizer schematic by way of the link in the previous post it appears that the 7.4 Mhz OSC. is not working in the radio. I have the proper voltage on the base of Q10. But, if I pull a crystal and check voltage at the crystal socket I have 0V. I believe that I need voltage at the socket for the Crystal to operate. So, does this mean that the switch S1-3 is not making contact? If you look at the schematic and see other potential failures that could cause this OSC to not work please share them with me. I am also going to check the CR204 Diode (1s1007). Any thoughts?
    Thanks.
     
  3. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
    1,271
    Nov 28, 2011
    I think people are interested, and we have members who have all kinds of experience, but if you don't get any answers, it's probably because no one who is experienced in that field, or with that type of circuitry, has logged in and seen your post yet.
     
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