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President Zachary T

Discussion in 'General CB Services Discussion' started by Stuck in the mud, Feb 17, 2021.

  1. Stuck in the mud

    Stuck in the mud New Member

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    I have a President Zachary T I am new to trying to fix my own CB'S. I have a Digital Multimeter, Multi Function Tester TC1, and a Sams Photofact Volume CB122. The receive works great on this radio. But when you key the mic the TX lite comes on but the meter on the radio swings backward and the external meter does not move. I have checked my SWR and I am at 1.0 on ch. 1 ch.40 also. I have checked the voltage on the main board and everything seems fine . Any help would be greatly appreciated Thanks Dale


     

  2. sp5it

    sp5it Master of puppets

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    Take RF probe and go backwards from final transistor to see where RF disappear.
    Mike
     
    Christopher17 likes this.
  3. Stuck in the mud

    Stuck in the mud New Member

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    I don't want to sound stupid but are you talking about using a signal tracer? And if so what sound will I be tracing. I am new sorrry
     
  4. Dmans

    Dmans Sr. Member

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    http://www.directdirt.com/2014/10/simple-home-brew-rf-probe/

    Google is your friend. Above is a link to build your own. There are many other links to build or buy one. They are simple and cheap to build on your own.

    An RF probe "traces" RF.

    You should be able to make your own RF probe or let someone else troubleshoot your Zachary.

    73
    David
     
  5. Robb

    Robb Yup

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    You need a 50 ohm dummy load and a reliable watt meter to accurately work on the TX - for starters. You cannot use an antenna, as that is a reactive load. A dummy load is purely a resistive load and will not vary.

    Might be an issue with the power supply not delivering enough current to run the radio when trying to TX. The radio needs only a small amount of current to RX.

    Is the dead key ('no modulation' transmit) set to 4w?
    No more than 5w dead key - tops

    Could be a lot of things. A pre-driver, driver, or final transistor getting weak. Failing capacitors in the TX circuit. Poor alignment of the radio - too . . .

    http://www.cbtricks.com/radios/president/zachary_t/zachary-t_block.pdf

    Think I would start at the power supply and test the electrolytic caps. Any of them hot getting warm? Could be a sign of failure. Test the voltage output of the supply, it should be set to no more than 13.8v. Replacing old caps in an older radio - especially in the power supply - would be my first guess.
     
    #5 Robb, Feb 17, 2021
    Last edited: Feb 17, 2021
    tecnicoloco likes this.
  6. Shadetree Mechanic

    Shadetree Mechanic 808 On The North Side of Dover

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    Does it work in pa mode with an external speaker? This will tell you if most of the audio circuit from the mic works.
     
  7. nomadradio

    nomadradio Analog Retentive

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    First thing I would want to know is if the radio really is receiving the channel that's selected. If the radio's PLL loses its grip on the channel frequency, FCC rules require a circuit that locks out the transmitter. And if you're certain the radio is receiving on the right channel, this is where a five-dollar yard sale CB with a coax jumper on it can pay for itself. Plug the coax jumper into the second radio and set it to the same channel as the broken one. Unscrew the shell of the coax plug at the other end and back it down the cable. Now you have a half-inch long "sniffing" antenna on the end of that plug. Remove the broken radio's case and key the mike on the broken radio. See if you can hear anything at all in the monitor radio, or see the S-meter flicker. Sniffing around the transmit section can reveal a weak signal it won't hear a foot or more away.

    If you can see a weak signal, even if it's only a carrier with no audio this tells you your transmit signal is being produced, but not amplified.

    And if you don't hear anything at all, this shifts focus AWAY from power stages like the driver and final. A total lack of any response in the sniffing radio points to a fault in the lowest-level transmit circuits.

    73
     
  8. Stuck in the mud

    Stuck in the mud New Member

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    I will be back on here later. I found out I did have a bad driver will be back on when I receive it. Thanks Dale Ps I sure do appreciate all the help
     
    Shadetree Mechanic and Dmans like this.
  9. Dmans

    Dmans Sr. Member

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    Stick with it.

    Inch by inch is a cinch.......yard by yard is very hard!

    73
    David
     
  10. Shadetree Mechanic

    Shadetree Mechanic 808 On The North Side of Dover

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    Glad you got it nailed down, let us know how it goes.
     

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