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cobra 148 gtl no rx light

kaos513

Sr. Member
Apr 10, 2014
2,389
731
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44
Putnam county,NY
Hello guys i have another 148gtl made in china the folowing is working : channel display,tx red light ,meter light.what does not work is the following: rx green light ,rf power, modulation all modes.
 

Hello guys i have another 148gtl made in china the folowing is working : channel display,tx red light ,meter light.what does not work is the following: rx green light ,rf power, modulation all modes.
Final and bias are good, pll is good voltage regulator is good am regulator is good as well.
 
fixed rx issue final hadcold solder joint but now i have no tx light when i key up or no am power, also r130 smokes when i turn on radio. i did replace r130.
 
The schematic I'm using says "Cobra 148GTL-F", June 27, 2006. But doesn't say which pc board number.

If it's the right one, R103 is a 470-ohm resistor. It provides the base current to turn on TR44 in receive mode, so long as TR46 has base current. Keying the mike shorts across the source of base current for TR46 and shuts off the receive side when the mike is keyed.

Really sounds like TR44 is shorted. The schemo shows it as a "LMB550". I would use a 2SB560, or any of a handful of equivalents.

The current that smoked R103 had to pass through TR46 to ground. I would replace TR46 as well. The marking "LC945" on the diagram suggests a generic 2SC945 is the same thing.

73
 
The schematic I'm using says "Cobra 148GTL-F", June 27, 2006. But doesn't say which pc board number.

If it's the right one, R103 is a 470-ohm resistor. It provides the base current to turn on TR44 in receive mode, so long as TR46 has base current. Keying the mike shorts across the source of base current for TR46 and shuts off the receive side when the mike is keyed.

Really sounds like TR44 is shorted. The schemo shows it as a "LMB550". I would use a 2SB560, or any of a handful of equivalents.

The current that smoked R103 had to pass through TR46 to ground. I would replace TR46 as well. The marking "LC945" on the diagram suggests a generic 2SC945 is the same thing.

73
 
So, what did you do to "fix" the first issue, and get the Tx and Rx lights to come back?

Please share.

73
who ever had this radio had the pll backwards i put in a new one and also had a bad solder job at the final and driver r103 has been replaced and i have no issues with it except i still have no modulation,recieve and power on all modes
 
who ever had this radio had the pll backwards i put in a new one and also had a bad solder job at the final and driver r103 has been replaced and i have no issues with it except i still have no modulation,recieve and power on all modes
i will test the rf amp believe its tr14 see if that can be the issue.
 

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