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Cobra 148GTL no Output power

OK. I've worked the switch and it seems to be fine. I'm changing from LSB to AM to USB as I TX on different radio and can RX it on the 148. Voltage during TX at finals drops of to 7 volts in AM mode but SSB there is no change. Full Power supply voltage -0.7 about.

BTW, Thanks for those schematics. Much easier to see! I used to go to CBtricks for info like that but can no longer find them.
 
longhaireddwb said:
OK. I've worked the switch and it seems to be fine. I'm changing from LSB to AM to USB as I TX on different radio and can RX it on the 148. Voltage during TX at finals drops of to 7 volts in AM mode but SSB there is no change. Full Power supply voltage -0.7 about.

BTW, Thanks for those schematics. Much easier to see! I used to go to CBtricks for info like that but can no longer find them.
Click to expand...

Ok, looks like the "patient" has a heartbeat...

Get to know that chassis - because there's parts on there that you will need know not just where they're at and what they do, but how to adjust them properly.

Right now, 7 volts an the "AM side" will give you a 5 ~6 watt carrier in a properly tuned Cobra and its' modulation may be a little low because the carrier is a little too high.

If This Were My Radio:
  • I'd be looking into protecting the investment I'm putting into it
    • Get Familiar with the chassis...
    • Know where your adjust pots are...
    • Keep things on the low-side in power and voltage so you can reduce the damages if the unfortunate were to occur...
These are just observations...keep going...
  • Also know that you are now getting power into sections that are sensitive to imbalances
  • - best ideas right now is to put a "Dummy load" 50 ohm'er on the Antenna jack and the power supply fused with smaller 4-amp or less fuses to keep any possible shorting-out damage to a minimum,
  • - If you haven't already done so, put the radio on a power supply that has short circuit protection ALONG WITH those fuses
  • CAUTION - these things use capacitors for filtering so if a short were to develop - these Electrolytic's can dump a charge thru the short in quick order,
  • When you are not sure of a step, locate the parts on the schematic then look on the board to find them, they are not always placed together...
    • THINK THE STEP THRU in your head - then perform it - it's a lot like acting or practice, which is what repairing is,
    • think of yourself like a Doctor, your performing a practice - a repair...only on a radio and you have to be careful with the patient and perform the step the right way and in the right order (or turn) of motion.
You can do this - we are here to help you. Rome was not built in a day...
 
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20190513_145848.jpg

If i look hard enough in my radio room i might be able to find a dummyload or three.

Problem is i still have no carrier/output power. Audio is alive and well. The tx/rx light changes as it shoild but no carrier.
 

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