148 GTL burned wire and no power on

[LocomtvBreth]

I have a Cobra 148 GTL that it did power up, but does not anymore. It is fairly new to me and I do not know its history, as I got it from a wrecking yard.
A negative feed wire from an add-on IC board has burned, and a couple resistors on the same board are blackened.



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Tuesday, 27 August 2013, 17:49 PM

Any help in repairing would be appreciated.

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Tuesday, 27 August 2013, 18:10 PM

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[Deleted User 14541]

It looks like an echo board that was not installed very neatly. Does the radio pop a fuse when you turn it on or just do nothing? The problem might be solved by removing the board and reconnecting the audio wires or it could have caused a lot more damage when it shorted out. This is going to be a tough one to fix over the internet.

[LocomtvBreth]

I would be totally OK with removing the echo board. I would need someone to hold my hand while doing it though. I've recapped a video card before, but never performed radio surgery.

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Tuesday, 27 August 2013, 20:18 PM

There is no fuse on the power line. I'm guessing I need to remove the red circled switch and put the green circled switch back in its place.

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[Z-MAN]

Looks like he grounded it wrong and it might of shorted out on the transformer too. Pot is not secured and not protected (not sure which one they removed for echo control pot) I wonder where they got switched power from also. The echo board should be mounted, not laying there or tied unprotected.

[LocomtvBreth]

Ok I removed the pot for the sound toy, and replaced the pot for S/RF, CAL, SWR. There is a yellow wire loose that I believe should be soldered to the lug empty lug with solder on it (both marked red), I do not know if I should reattach it.

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I also unsoldered the two leads from the toy to the mike cack and a lead off the dynamike pot, and soldered the dynamike lead to the mike jack.


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There was a brown lead from the toy that was soldered underneath the main board which I unsoldered as well.

Here is the toy after the surgical removal.

Pleas let me know if you see any mistakes as this is all based on assumptions.

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Wednesday, 28 August 2013, 20:28 PM

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[Deleted User 14541]

You can leave the yellow wire you aren't sure about disconnected for now and the radio should power on. I was concerned the echo board was shorting out and blowing fuses or tripping the power supply. If it still doesn't come on you have deeper issues,

[Z-MAN]

Im gonna take a wild guess and say that is a cheap/crappy Astatic echo/reverb since it has a brown power lead for 8v not 13.8v like the much better RF limited Turbox2's. Is the radio okay?

[LocomtvBreth]

The radio is still dead.

[Deleted User 14541]

You may be in over your head. A decent tech might charge $20 to fix it if its simple. If you can follow a schematic you can find one on cb tricks. Start tracing where power comes in and check components as you go. Have you taken a close look at the board for burned components? Maybe a shorted am regulator it's a 3 leg transistor mounted to the case near the power plug. I've shorted one and it killed power to the radio. Mine actually popped and had a hole burned through it. You can also flip the radio and look at the top of the board for burned traces. If you find a burned one you have two options. You can scrape the green coating off the trace to expose the copper and solder a small wire in place to repair it or you can follow the trace to the two nearest points and solder a wire from point to point.

[LocomtvBreth]

Fixed it. I hooked it back up to power and found that it was working, so I started wiggling wires and found a wire with a loose connection to the board. It was one of two wires with melted insulation. I replaced both wires and golden now. I also reconnected the the yellow wire to the pot.

The two melted wires.
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And the replacements with a bit of a curl to them.
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[Deleted User 14541]

Glad you got it working. These old 148s are good performers.

[LocomtvBreth]

After fixing the power problem and getting my antenna up, I played with the radio and thought I ran into another problem. The upper and lower side bands weren't working , or so I thought. Then I saw mention on youtube that there is no carrier wave with ssb. I went back out and hooked the 148 and tried again, this time talking into the mike. woot Pegging the needle on the 15 Watt setting, and looks like 20W on the high setting . Now I need to start calling out.