Question about Cobra 29 LTD CB Radio

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Trying to lower dead key

I was told to turn the pot next to the final i am not shure what pot that is? do you have a number for this pot

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Hi and welcome to FixYa,

Appreciate the direct "Ask Me".

Offhand the only "pot" near the final would be VR5, but that is used the S/RF meter. The other would be VR4 used to limit/increase modulation.

If I may ask, are you tweaking the radio? Pls post back.

Good luck and Thank you for using FixYa.

Posted on Jan 08, 2009

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You are talking about IF pot . For correct number you need to get service manual .

Posted on Jan 08, 2009

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1 Answer

How to turn up dead key on a cobra 25 ltd cb radio


There is not a magical pot to turn up the dead key like some exports have, the radio would need to be "tuned up" by a good CB radio shop.

Jun 21, 2014 | CB Radios

1 Answer

Want to lower my dead key on my cobra 148 gtl mobile...where do i find the adjuster?


need to get a watt meter hooked up to then go the where the final is and look aroung for a tuning slug marked L38 and that is the baby you have to turn in order to power down this radio.

Nov 09, 2013 | Cobra 148 GTL 120-Channels Base CB Radio

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The variabel key drops sometimes drops when radio is keyed up and sometime the RF power knob has to be turned farther to bring it back up on my Galaxy DX959.


I'm not shure if you have tried but turn the mic gain down then check the d.k output. If you still lose power after a d.k it could be a final it's hard to say w/o seeing it. Also an external meter is more stable than the internal one. Check your coax, make shure all are tight. If you need more help e-mail me at
herzjoe3@gmail.com. no capital's
Good luck

Feb 16, 2012 | Galaxy Radios DX-959 40-Channels Base CB...

1 Answer

77 HML finals


I'd start by checking the easy things.
1)Try a better meter
2) If your Standing Waves are high, that could be the cause.
If they are good (<1.5:1) continue to 2)
2) Try another microphone.if the second mic is just as bad it could be the alignment is off.
3) Perhaps the bias adjustment to both finals and the driver are wrong. People do go in and turn them sometimes :-(
4) Maybe the output finals are soft.
You can probably change the transistors yourself as long as you have good soldering skills, eyesight, a steady hand, the correct tools, some heat sink compound, and the ability to correctly retune the output stage.
If not, pay someone to do it correctly. You don't want to end up with an anchor (and not a very good one at that).

Apr 08, 2010 | Galaxy Radios DX 77HML Base CB Radio

1 Answer

Cobra 29 classic "swing kit" ?


A swing kit is nothing more then a Cap and a resistor. There really isn't a different way to do a swing kit, unless you do variable power, which you don't need unless you are going to run a linear, and even then you can just set the dead key with a swing kit.

you need a watt meter, preferably one that reads peak and average watts. If not, average will be find.

Open the bottom cover of the radio. Hook the radio up to the watt meter, use a dummy load or have it hooked to the antenna. Never key the radio with an antenna or a dummy load.

Find VR4. Its toward the back right of the radio. Turn it all the way to the left. That increases your modulation.

Next find L14. it is at the back in front of the final resistor. While making a steady sound into the radio, just make an ahhhhhhh noise. Back the slug out of the tank until the needle hits peak. Don't move it out any more or you will over bias the final.

Now you will need a 220 uf electrolytic cap, and a 100 ohm 1/2 watt resistor, both of which you can get from radio shack. (this is your swing kit.

To the right of the tank slug is a jumper maked JP36. Us soldering wick to remove the solder and pull out the jumper. Now put the cap in it with the stripe facing the back of the radio.(that is very important. the other way you will blow the radio.) Solder it in place and cut the extra leads off. Now on the back of the board were you soldered in the cap, solder the 100 ohm resistor in between the 2 points.

The amount of resistance determines you dead key. you will be at about a 2 watt dead key which is good for swing and if you want to run a linear. The higher the resistor the lower the dead key, and the lower the cap, the higher the dead key.

That is your basic peak and tune with a swing kit.


Dec 23, 2009 | Cobra 29 LTD CB Radio

1 Answer

How to adjust the dead key in a uniden pc78ltw


You change the dead key with the addition of 2 components to the board. There is no dial or pot inside to turn to adjust the dead key.

What you want to do to the radio is called a swing mod. If you are trying to adjust your dead key, it sounds like you are trying to run a linear amplifier. If that is the case, you should probably set your dead key to around 2 watts. Most amplifiers are good with 2 watts. If this is so, then do this:

Go to radio shack and get a 1/2 watt 100 ohm resistor, and a 100uf 35 volt electrolytic capacitor.

Open the radio and look for JV117. It is a jumper. It is located in the back left of the radio in front of the final resistor in front of the heat sink.

Use a de-soldering wick to remove the solder from the trace side of the board. Remove the jumper.

In the jumpers place put the capacitor. Make sure the black tab is facing the back of the radio, towards the final. This is very important because there is a positive and negative to the capacitor. If you do it backwards you can blow your radio.

Solder in the capacitor, then take the resistor and on the side you soldered, solder the resistor bridging the 2 pins of the cap on the trace side of the board.

How this works:

The resistor determines the amount of dead key. the bigger the resistor, the smaller the dead key, the smaller the resistor, the higher the dead key. (dead key will only go as high as it was before you put in the mod.) A 100 ohm resistor gives you about a 2 watt dead key.

ALSO! you are going to want to find VR4. Its a little pot towards the back right center of the board. Then turn it all the way to the left. This turns up your modulation, and will make the radio swing to full PEP wattage, around 20 watts.

If you have a watt meter that reads avg wattage then you can gain more wattage by adjusting L14. It is just right of VJ117. it is a white or brown plastic tank with a copper coil around it with a slug in the center covered by a little way.

*do this only if you have a meter, also, do not transmit on your radio without an antenna connected or a dummy load or you will blow the final.*

Remove the wax and then while saying a steady ahhhhh sound, slowly back out the slug until you have peak wattage,(when the needle no longer increases.) You do not want to back the slug out any more then is needed for full wattage, other wise you over bias the final and lessen the life of it. So once the needle stops going up while giving a steady ahhhh into the mic, back it in a hair just to make sure its not over biased.

And as always, if you are not comfortable doing this your self, take it to a radio tech at a radio shop. They are usually found at truck stops.

Oct 15, 2009 | Uniden CB Radios

1 Answer

Tunring up a cobra 150 gtl/dx


Um... What?? This is hooked to a switch? CB radio by FCC regulations is only supposed to have a max of 4 watts total output. If you can flip it to 7 watts dead key, you are doing really good. It won't do much more then that. It sounds like its set up to run on a linear amplifier, which cannot have more then 3 watts dead key transmitting into it.

Dead key, and modulation are different. You may have a meter that only reads dead key, and won't see the modulation. This radio is probably swinging close to 15-20 watts. you need a meter that can read PEP, Peak envelope power. Cheap meters only read AVG, or average power, witch will only show your dead key.

7 watts dead key is really good for that radio.especially since stock only has 4 watts. you cannot get any higher then that without changing finals.

at 3 watt dead key, or 7 watt dead key, your modulation wattage is still swinging much higher.

Also, you will get more swing with a lower dead key any way, which is better if you want it to be loud.

Leave it alone. its probably set just right.

May 12, 2009 | Cobra 150 GTL DX Base CB Radio

1 Answer

Modulation with my linear


the radio you are trying to fry your amp with is driving the amp to hard. that radio has a toshiba 80 watt final inside the radio you are killing your radio with the dead key at 2 watts it causes the final to overheat and shut down because it is not built to be turned down that much. its best to turn the radio back up and use the radio.

Mar 07, 2009 | Cobra 29 WX NW ST 40-Channels Base CB...

1 Answer

What is the number on the pot next to the final that i have to turn out?


Offhand the only "pot" near the final would be VR5, but that is used the S/RF meter. The other would be VR4 used to limit/increase modulation.

Jan 08, 2009 | Cobra 29 LTD CB Radio

4 Answers

Not enough watts


All he is asking for is this...

Find VR4. Its near the big transformer. Turn it all the way to the left. That is your AMC. that will turn your modulation all the way up.

If you have a power meter you can raise your dead key, or carrier signal as raising the modulation only effects your swing.

If you don't have power meter, then don't mess with it. Increasing the modulation will be a big improvement.

If you do have a power meter then here is what you do. Find L12 near the final, is near the heat sink in the little space near the transistor. that is your final. Turn this out, to the left, with the radio keyed until the needle stops moving up. don't turn it out any more.

***** NOTE IMPORTANT *******

Do not do this with no antenna hooked up, or without a dummy load. You will blow up your final. You can never key the radio with out a 50 ohm load on the radio.

You can make a simple dummy load to do this inside instead of out in your vehicle. Take a CB coax and 5 150 ohm resistors. Hook the 3 ends of the resistors together and solder them, and do the same with the other side. then solder on end to the center piece of a coax, and then to the out side piece. that will give you a 50 ohm load when you connect it to the radio. If the Ant light goes on, stop right away you did something wrong.

You will also need a power supply. If you have an old computer, you can use the power supply from it to power the radio. Yellow wire on one of the power supply ends to the red wire, and the black can go to either of the black wires.


If you are not sure, just increase the modulation with VR4. that will make the radio swing to about 20 - 25 watts.

Sep 08, 2008 | Cobra 29 LTD CB Radio

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