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I have a cobra 29ltd crome had echo board installed works good till i trun my la 900 on get feed back or squilling how do i fix

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LA 900? I am guess that is a linear amplifier. If so are you running a power mic? You are probably getting RF feedback. You need to turn the gains on the radio and mic down.

Some things you can try. Hold the mic cord in your other hand in the center of the cord while you key it. some times this will shield it form stray RF.

You can also get a bunch of RF chokes from radio shack. They are little black things you snap onto wires that shield form RF. Put 2 near the plug, and 2 near the mic. That will help shield it from RF.

you will most likely still have to play with the gains on the radio and mic to find a sweet spot where it doesn't squeel.

Posted on Oct 10, 2009

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I have a cobra29 wx nw st. its been peaked and tuned, an echo board installed, and soundtracker override when i key up if my mic gain is over 1/4 the way up it makes an awful racket what do i do?


is there talk back installed? if so its probably too loud. You are getting feed back. The talk back should be low, just enough to hear it to check echo. 470 ohm resistor is perfect.

Jan 04, 2010 | Cobra 29 WX NW ST 40-Channels Base CB...

1 Answer

I have a Cobra 21- 23 channel CB and the wires pulled out of the plug. The mike wire has red,yellow black,blue,whiteand a ground. My plug has only four prongs to solder to. What four colors do I use?


Hello there
Here is the diagram for you
Cobra 29LTD, 29LTD ST, 29WX ST
Documentation Project
CBTricks.com

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25ltd_st_sm.jpg
Click Picture to See Close-up
cobra_29ltd_st_29wx_st_side.gif 29LTD ST Owners Manual pdf_1.gif
29WX ST Owners Manual pdf_1.gif
DIAGRAMS
29LTD ST Schematic Diagram pdf_1.gif
29LTD ST Schematic Diagram gif.gif
29WX ST Schematic Diagram pdf_1.gif
WX Schematic Diagram pdf_1.gif
29LTD, 29LTD ST, 29WX ST Factory Service Manual pdf_1.gif
Page 1 to 11
Page 12 to 34
29LTD Factory Service Manual pdf_1.gif
29LTD
29LTD Schematic Diagram pdf_1.gif
29LTD Schematic Diagram jpg.gif
29 LTD Classic Schematic Diagram pdf_1.gif(Courtesy of Rick Jackson)



Mic Wiring
Stock
1- Shield
2- Audio
3- Transmit
4- Receive
Astatic (4 wire)
1- Shield
2- White
3- Red
4- Black

Astatic (6 wire)
1- Shield & Blue
2- White
3- Red
4- Black
Yellow NC
Daiwa EM-500
Cobra CA Series

1- Shield & Black
2- Red
3- White
4- Blue
Galaxy DC-521S (4 wire)
1- Shield
2- Yellow
3- Red
4- Black
Galaxy CB-660EI
1- Shield & Black
2- White
3- Red
4- Blue
Sadelta
1- Shield
2- White
3- Brown
4- Green
Turner
1- Shield & Red
2- White
3- Blue
4- Black
Yellow NC

Nov 17, 2009 | Cobra 29 LTD CB Radio

1 Answer

Lot of fed back


Make sure the antenna has a good clean ground. I know it sounds silly, but here's what's happening: You're getting RF feedback. If you don't have a good ground at the antenna, some of the RF travels back down the coax and makes the whole radio "hot". Some of that RF couples back into the microphone input, and causes feedback.

It's also possible that if your amp is really big, you're getting RF feedback directly from the antenna itself due to the really strong field.

You could try moving the antenna further away from the radio, or if that's not practical, some snap on ferrite chokes (available at radio shack) around the mic cable near where it enters the radio will probably solve the problem.

Oct 06, 2009 | Galaxy Radios DX-66V Base CB Radio

4 Answers

Feedback problems with astatic echo boards


This is a classic indication of a lost shield or ground connection in the mic circuitry. Double check these connections for good contact in the mic *and* the plug at the other end of the cable.

Check the grounding and SWR or "match"of the antenna system, too. A poor SWR (greater than 1.5:1 or 2.0:1) can cause the reflection of RF back to the radio. Modifications can increase sensitivity of the mic to this unwanted RF.

Sep 29, 2009 | Cobra 148 GTL 120-Channels Base CB Radio

1 Answer

Installing an Astatic Echo Board in a Cobra 148


There should have been instructions that came with your reverb board. You are going to need to drill another hole in the case of the radio, or find a control where you can install a dual control knob onto.

Your reverb board is likely going to need 8v, so you will need to locate that off the logic board, likely from the frequency synthesizer. The the audio lines from the mic, or the output of mic amp, are going to be redirected to the reverb, and the output of the reverb feed back to where the wires were removed from.

If I recall correctly, the 148 is a bit of a bear to work with, not much room inside. You will likely have to get creative in placement of the reverb board itself. Make sure to wrap well so that it doesn't get tossed around and break something inside.

Sep 15, 2009 | Cobra 148 GTL 120-Channels Base CB Radio

2 Answers

Help with cb radio


Hello there
here is a link for the scematic ok?
best regards michael

  1. Cobra 29LTD ST, 29WX ST 29LTD ST Owners Manual. 29WX ST Owners Manual. DIAGRAMS. 29LTD ST Schematic Diagram ... WX Schematic Diagram. 29LTD, 29LTD ST, 29WX ST Factory Service Manual ...www.cbtricks.com/radios/cobra/29ltd_29ltd_st_29wx_st/index.htm - Cached

Sep 15, 2009 | Cobra 29 LTD CB Radio

1 Answer

Scematic


Hi and welcome to FixYa,

Pls click on the schematic diagram for a Cobra 29LTD.

Good luck and Thank you for using FixYa. Happy Holidays.

Dec 11, 2008 | Cobra 29 LTD CB Radio

2 Answers

Scematic


Hi there!!

If you have an echo board what kind is it? I can give you the connections and where they go it just depends on which echo board you have!! I can also tell you where that talkback goes!! Let me know

Dennis

Dec 10, 2008 | Cobra 148 GTL 120-Channels Base CB Radio

1 Answer

Feedback


Assuming you have a good SWR, either ditch the power mike or the truck.

Aug 23, 2008 | Cobra Radio Communications

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