Question about Cobra 29 LTD CB Radio

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

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  • Louie  Role
    Louie Role May 11, 2010

    Hi and welcome to FixYa,

    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.

    Good luck and Thank you for using FixYa.


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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.

Posted on Jan 10, 2009

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Can you turn the rf gain pod up for better receiving

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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.

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Midland 77-099 Modulation/AMC pot?

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I have a galaxy 44v that recieves keys up but know watts come out i have put new finals new voltage regulators b754 and the one in front of it changed the 300v redish " dog tic" thats what we...

  • The Galaxy 44 has 1 final and 1 voltage regulator not "finals." I doubt it is putting nothing out although it may look like it on a watt meter. Check VR16 (low power adjustment for the amp) and VR 13 (High power adjustment) for the amp in the radio. That radio has a variable power so make sure the pots were not turned out of whack. Check VR 14 as well. this is your AMC modulation pot adjustment.

  • Test the driver as well as the pre-driver. Check your microphone to make sure the wiring is good and the PTT is functioning.

  • If you have any comments please feel free to leave them here.
  • Hope this helps and thank you for using FixYa.

Regards, Tony

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1 Answer

I have installed a supermod on my radio clipped d11 and added varible pwr to the delta tune knob it worked fine for a couple of days the varible was touchy now it will key up but will not modulate. i...

  • Why would you cut d11 when you can adjust VR4 and have it sound so much better? When you cut d11 you put that modulation into overdrive. Put that diode back and adjust VR4 for 100% modulation. That is step one.
  • I assume you added variable power from J36. The problem with adding variable power and not switching the pot is that the wires not only have major loss, running to the pot. And two the stock potentiometer tend to burn up if not replaced with a potentiometer that adjust power by itself. Undo this so called "super mod."
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  • You can pull the ferrite out of the pot next to the final transistor or you can remove j36 and add a 330uf capacitor (black stripe, negative) to the rear and bias the soldier side with a 33uf resistor. Soldier the resistor to the same soldier points of the Capacitor.
  • Adjust L14,L13 and L12 for power.

Regards, Tony

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1 Answer

Gme electophone tx it possible to turn up mic gain on my uhf rig?if so which pot do i turn?thaks in advance ajax66

  • To boost modulation you need to add another diode in series to the diode located next to C92, it will reduce the power a little bit but it does help give the radio more modulation.
  • The AMC itself is the middle pot under the wires towards the front.
  • If you want to do a receive alignment you need a Oscilloscope. Peak on Ch19 T1 - T2 - T2a - T3 - T4 - and do this with a little signal level as possible from the Oscilloscope. Then set the Oscilloscope to -67dB output no modulation and adjust RV1 to not quite light the +30 LED.

You are now set.
One more thing, The finals are a strait drop in. So if one goes just drop in a replacement.
Regards, Tony

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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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