On the Cobra 29 LTD, What number transistor, and diodes do I swap for the Schottky receive upgrade . I was told that they may be: TR-7, D-5, D-6, & D-24 . I have the Sanyo 2SC2999 Transistor, and the Shottky 1N6263 Diodes .

Check transistor TR 15 and TR 16. They are the driver and the buffer. Adjust L 16 and L 17 if no change check L17 L20.

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Cobra 29 LTD Classic CB Radio - YouTube? 5:42https://www.youtube.com/watch?v=vJle8vlsWLcAug 20, 2013 - Uploaded by C B WorldIn this product review we look at the Cobra 29 LTD Classic CB radio and ... Just like in the manual. most channels are below 3. a few are not.Cobra 29 LTD Classic Troubleshooting - iFixithttps://www.ifixit.com/.../Cobra_29_LTD_Classic_TroubleshootingiFixitCobra 29 LTD Classic is not transmitting or receiving. The Antenna is not tuned correctly; The Radio is not in CB mode; The Radio is on the wrong channel; The ...Marine Radios ' Cobra Electronics Corporation

If it is the original 29 LTD, D11 is a IS2075K Diode. Attached is a section of the schematic showing the diode. Check the components connected to it to verify if they match those on the schematic section below. If they do, you should be fine installing the listed Diode. If they don't you may not have the model of Cobra 29 listed below.

I am unaware of any dramatic improvement from tuning or germanium or schottky diode swaps in rigs that are the solutions in cobra 29 and galaxy radios.
You will see more promising result from a good quality antenna (wilson 2000 and coaxial cable 95% shielded. Then consider a preamp for improved RX however the nature of the AM band that cb radios operate on is overran with interference when you amplify the reception you also increase the noise and the filtering just is not there in these units.
The cobra 19 and uniden 510 such radios are very popular but cheaply made units you would be much happier with a Cobra 29 Chrome which is inexpensive but in my opinion has better reception than the cobra 29 ltd with the soundtracker gimmick.

May be transistors or burnt resistors near back of radio.

Hi, my name is John. Welcome to FixYa. TR-12. #LC945Q, R-45 10K. VR-202 50KB. Thanks for choosing FixYa....John

really the only thing you can do to the radio is make sure it is aligned, and that it is receiving on frequency. Although this unit has a frequency counter that will tell you where it's receiving, you cannot successfully put the radio on frequency unless you fully align the radio. In order to align a radio you need a volt meter, watt meter that reads avg watts, and an oscilloscope.

A volt meter and watt meter is easy to come by, however the oscilloscope is an expensive piece of equipment to attain.

You can just as easily tune your clarifier to the correct receiving frequency on the counter.

An easier way to improve your receive on any radio is to make sure the antenna is tuned for best SWR. When an antenna is tuned to the proper length for the best SWR your receive will get better because your antenna will be on Que.

There is also a Schottky diode upgrade that can be done. This consists of changing the detector diodes in the radio to schottky diodes as well as changing a transistor. This mod improves receive in most galaxy radio a great deal.

You can get these as a kit with full instructions on ebay fairly cheap.

You need to replace diodes D1, D2, D23, D24 with the schottky diodes in the kit, then replace TR-17, with the transistor that comes in the kit. Then remove TR-14. and them remove TR-19, and put the transistor from TR-14 in the TR-19 spot.

The Transitor that goes into TR-17 is a 2sc2999. I can't remeber what the Schottky part number is. But like I said, they sell the kits with complete instructions on ebay.

Here you will find all the technical information about your radio, as well as alignment guides.

Here is a link to ebay with an upgrade kit and instructions on ebay.

If the receive works ok,sounds like a mic
problem,try another mic if you can find a
buddy who has a Cobra that may let you
try it most all Cobra mic will work but not all.
Good Luck

If it is classic it is a 2SC2029 driver transistor.

Hi,

Your concern is no transmit and no red transmit led -

If there is no receive likewise, then probably problem in the PLL/VCO section or 9V voltage regulator TR23 (2SC1096) or Zener diode D22 (9.1V).

If the receive is normal, then possibly any of two (2) faults:
1. microphone/PTT switch and/or the mic cable specifically the wire connected to pin# 3 of the connector; or
2. +8V switching transistor TR21 (2SA733P).

Hope this be of initial help/idea. Pls post back how things turned up or should you need additional information.

Good luck and kind regards.

Thank you for using FixYa.