Question about Cobra 148 GTL 120-Channels Base CB Radio
The problem with these radios (I have owned 4 of them and also repaired them) is that if they were "tweaked" too high several bad things can happen.
If you have both AM and SSB transmit but it is very low output--suspect either the Driver or Final transistor are bad. You will need to unsolder all three leads (ECB) on each transistor and test them with a ohm meter.
If either is bad----replace both--also note which transistors are in the radio--some people will replace them with "higher" output transistors to get more output.
If the radio had modifications for a carrier control---it would only affect output on AM.
The weak point in this radio if it has been tweaked is the voltage regulator IC located on the right wall of the set next to the audio output IC chip.
Checking voltages will not really tell you very much---Confirm first the actual condition of Driver and Final transistors. Some good advice would be if replacing them restores transmit instantly lower both AM and SSB output either with the controls or by alignment of the driver and final stages of the radio.
The fact that the radio was dimming the meter lights before is a dead giveaway that the radio was pulling maximum voltage from the regulator IC in the radio's power supply.
Something else you may want to try that may or may not confirm this is switch the switch on the back of the radio and connect it to the DC power socket----IF RADIO WORKS THAT WAY-internal power supply is damaged and not the Driver/Final stage.
Let me know what you find.
Posted on Feb 05, 2010
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Posted on Jan 02, 2017
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