Question about Cobra 29 LTD CB Radio

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I have a 100 watt board inside my radio and when I turn the power on I get a buzzing sound.

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THE WIRES TIPS ARE CUT OFF

Posted on Apr 01, 2010

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Wire is shorted perhaps?

Posted on Mar 01, 2010

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I have a nissan maxima ,and i think i shorted something out ,while hooking up the radio,which in turn the car wont turn over and have a buzzing sound from inside the auto


First I would unhook the radio. Some of the wires to the radio are communication lines. Put power to the wrong wire and it can burn out computers.

Jul 24, 2016 | 2001 Nissan Maxima

1 Answer

Big finals and how to install them for radio shack trc-447


It doesn't make a difference how big your final is the radio will not except it. What I'm saying is if you install a 100 watt final into it ,no matter what you will only get a max of 25 watts because the radio cannot handle the 100 watt load.No if you start changing components inside the radio to obtain the 100 watts you are now in violation of fcc rules , unless you are a licensed tech , if you were then why are you asking this question. The best thing to do do is get a 100 watt amp and hook it up. you will be smoking the neighborhood.

Aug 28, 2013 | Radio Shack TRC-447 CB Radio

1 Answer

MI CB COBRA DX-19 IV when someone ear me say i don t ear you well sounds like bad voice or no good my voice..


try turning you radio power down to 1 watt and see what that does .the asskicker 100 watts is being overdriven by the radio power and its coming out sounding horrorable . How many watts does the radio put out now? the lower the better like I said in the begining 1 watt is best with a box.

Mar 28, 2013 | Cobra 19 DX IV CB Radio

1 Answer

Can you turn the rf gain pod up for better receiving


Yes you can turn up VR pot inside to recieve max level but will cause noise to be max too. I don't rightfully remember which one does it but I'll refer you to Defcom cb radio mods for a spec sheet
or Snakedoctors cb radio mods google site. Go to these radio mods sites on Google search and type in radio model. It will tell you what Vr inside to turn up RX of RF gain. Turn up modulation and written instruction if you are handy with solder gun how to change a resistor or cap to make it more sensitive recieve. How to replace final stage and resistors to 1/2 watt size for 6 more watts output and spread coils 1/8 inch apart like a comb for 100% microphone loudness or swing output. say 3 watts to 40 watts output. More windshield wiper swing in meter makes loud voice and extends range with Power final boost. Most people prefer to keep a mobile at around 11 watts swing to 45 watts.(but on generic radio meter will show 2 to 5 watts-its not accurate just a cheap indicator you are forward swing). Even though factory says 4 watts FCC hogwash. They come tuned from Cobra with 11 watts to 14-22 watts.Cobra really peaks them babies so competition doesn't beat them out like new louder radios made by Galaxy 55. Even though law says blah blah (corporations bend it)sales pitch Galaxy very heated with Cobra on the game(rich can do what they want)Galaxy is 20 watts factory with big promise to 40 watts dual finals. So Cobra updated and said "screw it we will break the law too" Now Cobra is loud as ever and offering their own super mod versions and dual final radios with 45 to 65 watts output with ranges on SSB & USB of 1500 miles on a strong good outdoor antenna.

Feb 15, 2013 | Cobra 29 LTD CB Radio

2 Answers

Is it possible to convert the cobra 29 wx nw st sound tracker cb to 10 meter amateur band?


No it cannot. If you want that buy a Ranger or a Galaxy.

The 29 can be altered to increase modulation and turned down in power to match it to amp for increased output of power.

Set to dead key a watt or so with a 100 watt amp it would dead key low and swing to 80 to 100 watts pep.(peak envelope power)

Mar 16, 2012 | Cobra Radio Communications

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 Radio Communications

1 Answer

Tell me how to turn the raido power down to 1 watt so i can hook up my 350 watt liener? i need to find the schmatics so i can find the right knob to twist


There are no knobs for AM power in the cobra 29 LTD. Soldering 2 parts inside the radio is needed to do this. If you are not comfortable with soldering inside of the radio, take it to a technician.If you feel you are up to it, here is how you to do it.

First make sure VR4 is all the way to the left. This will turn your modulation to full and will make your audio louder.

Next you will need a 220 uf 35 volt capacitor and a 1/2 watt 100 ohm resistor.

Now remove JP36. It is located right in front of the final transistor in the back right that is bolted to the heat sink.

put the capacitor in its place with the black tab facing the back of the radio.( this is most improtant because if you don't face it the right way you will blow your radio). Solder it in place.

Next on the trace side of the board, where all the solder joints are, solder the resistor to the spots where the cap was soldered. So the resistor is in between the 2 points of the capacitor.

Now your dead key will be at 2 watts. Now, you did say you wanted 1 watt. From my experience, 1 watt is not enough. you will under drive the box and blow the pills in it.

If in fact you do need only 1 watt, you have to play with what size resistor you put on it. if you increase the value of the resistor, you will get a lower dead key. If you lessen it, it will make the dead key higher. Get a multi pack of 1/2 watt resistors if your going to do this.

BUT** 2 watts should be what you need.

So you know. There are 2 types of wattage outputs in an AM radio. There is carrier signal or dead key, and then there is modulation or swing.

Your radio is going to do 2 watts of a carrier signal or dead key, and when you talk the meter will swing up when you talk if you have peak reading meter. it it only reads average, it will only show your dead key with only a swing of about 4-5 watts.

For low drive amplifiers, the dead key is usually all that needs to be set. The swing should be turned up (thats why you turn VR4 all the way to the left) witch will give you just over 20 watts swing. this will drive the box good. Any where between 20 and 35 watts will dive most boxes good.

GOOD LUCK!!

Oct 09, 2009 | Cobra 29 LTD CB Radio

1 Answer

My 10 year old Bose wave radio quit working.


There's a line fuse inside the radio, mounted on a PC board. CAUTION: disconnect the set from power before opening the case or poking around inside. The fuse could be bad, but these sets are notorious for losing the power transformer. If the fuse is ok then you are looking at a $100 repair fee from Bose. You might want to check out the new HD radios -- better sound, MUCH lower price.

Bill B.

Mar 26, 2009 | Bose Wave Radio

1 Answer

148gtl, Taiwan when you modulate the meter swings backwards


In the back is where power mods have been added...It sounds like a swing kit 1/2 watt deadkey to 25 watts which is a powerful modulation exceeding 100%. Its a 220uf capacitor in place of a jumper J1 or J(x) J something in some radios. if you replace the jumper and remove the capacitor 220uf or 470uf one.(near finals it will return to around 4 watt dead key) The result of 4 watts is modulation is flat;where if you adjust it to 2 1/4 watt to say 20 watts it will be very loud and modulation is at 100%.

Dec 07, 2008 | Cobra 148 GTL 120-Channels Base CB Radio

1 Answer

Buzzing noise from radio


the sound is the generater's ac power and the rectifier that filters the ac to dc in the radio is starting to fail or a filter inside the radio is failing to filter out the ac power

Oct 18, 2008 | 1998 BMW M3

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