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President Zachary T

Nov 28, 2020
68
10
18
70
Muncie, Indiana
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
 

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.
 
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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
 

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