Question about Two-Way Radios

1 Answer

Cobra 29ltd classic : no rx / tx

Radio was plugged in backwards , with 3 amp fuse inline . I replaced d23 , and fuse ,brought it back to life .I tried several ( known good ) mics .Still no rx / tx .
Altho the rx / tx light does switch back and forth showing rx / tx

Posted by on

  • ejramsey Feb 05, 2008

    Thanks for advice , I will let you know how it turns out .

    Thank You

×

1 Answer

  • Level 3:

    An expert who has achieved level 3 by getting 1000 points

    All-Star:

    An expert that got 10 achievements.

    MVP:

    An expert that got 5 achievements.

    Brigadier General:

    An expert that has over 10,000 points.

  • Master
  • 6,966 Answers

Hi,

D23 is the reverse protection diode and it shorting is the primary reason your fuse blew. As you posted, power was applied in reverse, hence other components would also fail. Pls check:
1. D22 - 9.1V Zener Diode
2. TR23 (2SC1096) 9 Volts regulator
3. D19 - 5.1 Zener Diode
4. IC4 (TA7222) - Audio Amp
5. TR14 (2SC2029B/10) - Finals
6. TR15 (2SC2028B/20) - Driver
7. Most capacitors over 220uF (like C123, C114 & C112)

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

Good luck and kind regards.

Posted on Feb 04, 2008

  • Radio-tech155 Nov 12, 2015

    not all had a ta7222ap for an audio chip. they switched to a TDA2003 ..

×

Add Your Answer

Uploading: 0%

my-video-file.mp4

Complete. Click "Add" to insert your video. Add

×

Loading...
Loading...

Related Questions:

1 Answer

I have the CXT88. It's been a while since I dont use them. Now I can't get them to work.


Assuming these are Cobra CXT88 radios.
Manual: https://www.manualslib.com/manual/29293/Cobra-Microtalk-Cxt88.html

Make certain they are fully charged. I suspect the batteries. If the radio was left in the "on" position, it is very likely the batteries will not take a charge. The batteries can die in the drawer as well. Lithium batteries for all their good points really do not store well. (Yes, expensive lithium batteries such as your power tools or laptops do store well.) So, plan on new batteries. Many radios have become less expensive this year, so price out a new pair. That way you would have fresh batteries and a new charger.

Nov 05, 2016 | Two-Way Radios

1 Answer

Stuck on rx mode


Rx is an abbreviation for receive. (Tx is transmit) There are a variety of reasons a radio will be "stuck" in Rx:
1) Another radio in the group is stuck in transmit and you cannot reply if your radio is receiving the other radios transmission.
2) Your radio is programmed for Rx only.
3) Your radio has a Tx problem such as a bad mic, or something covering the mic opening.
4) Your battery is low or bad. It takes more energy to Tx than to Rx.

Best regards.

Feb 07, 2014 | Cobra LI3900-2DXVP (14 Channels) 2-Way...

1 Answer

Set to RX at 464.625


Get a radio that is certified for Part 90 operation.

Dec 05, 2013 | Cobra Two-Way Radios

1 Answer

Tk3312 will not recieve repeater but audio is fine and channels with out pl are fine


1- Did you choose the right Tone for both RX & TX?

If you have RF present but not the right tone, the green led should turn on.
One of the side key should be a Momentary "Squelch Off" (By default, it programs like that). Use it when you you see the green led turn on.

If you have the wrong Tone Squelch programmed, the side key will let you hear the repeater to confirm the problem.

2- If it didnt do the trick, Look for a RX/TX frequency mismatch. maybe your RX/TX frequencies are wrong for this channel?

3- If you have checked all the above, maybe your radio have a bad ceramic filter and your unit has lost it's sensibility. (Youll hear only people near to you.)
If it's the case, usualy only one half of the filter goes bad. Try swapping the Bandwith type in programmation. If WIDE, try NARROW or the opposite. If you receive in narrow but not in wide, the filter is bad. In more than 50 radios with Sensitivity problem, I only got one with both Wide/Narrow sides of filter bad.
If you have access to a spectrum analyser, on a "RX Test" you should see ~0.2uV. Anything higher than 0.3uV mean you have a serious RX problem.

Sep 06, 2012 | Kenwood Tk-3312 Uhf Handheld Radio

1 Answer

Best modulation for PC68XL


Most Cobra / Unidens are easy by clipping D9. On this one D9 and L19. Just turn up L19 to top. Clip D9 diode. spread coils 1/16" inch. Also use 100uf capacitor (-) toward final across JUMPER staple near Final Transistor in back. Use meter(adjust to best swing) spread back coils,remove L10,L20 slugs or adjust them to top. The only radio that clips different than D9 is Cobra 29Ltd (D11) or Uniden pro510xl(D14).

Oct 08, 2010 | Uniden PC68XL (40 Channels) 2-Way Radio

1 Answer

Cx80 stuck in rx mode , power cycled, swapped batteries, changed channels, will only swtich to tx when ptt button pressed, otherwise always in rx mode, other radio from package works fine


But thats how a walkie talkie works, it stays in Receive Rx mode UNTIL you press the PTT button,, then it Transmits Tx, and when released it goes back to Rx, receive?

Feb 18, 2010 | Two-Way Radios

1 Answer

One of my walkie talkie has an RX on the display and you can send but you cannot hear the other person. How can I remove the RX as that seems to be the only difference in them. Thank you


depending on what radio you have, they are programmed in different ways, rx means recieve signal

and tx means transmit signal, if you have a mode button, you will have to scroll through it until you

get to the menu that allows you to change the radio transmission. it looks like that radio is only

programmed to receive signals and not transmit. good luck!

Nov 11, 2009 | Cobra Microtalk 100 FRS Walkie Talkie...

1 Answer

My cobra hh-36st cb radio is stuck in TX mode. The RX/TX light is red each time it is truned on. Removing and replacing the batteries has not worked.


G'day,
I think your problem with the Cobra cb is in the microphone, you should have a plug on the Mic cord end ,try disconnecting this from the CB unit and see if it clears it self. If this does the trick your problem is in the Mic it self, or the cord has a fault in it. However if you still have a problem it may be that the transmitt/ receive relay located in the Cb is stuck on transmitt, sometimes this can be cleared by tapping the case with the handle of a screw driver, place towel on the case first to stop any damage to the case( this doe's not always work) you may in this case need to have it serviced
all the best hope I have been of help,
John

Apr 08, 2009 | Cobra Two-Way Radios

1 Answer

Blown fuse and reverse polarity diode


Check around the pcboard where the dc goes to the board, sometimes the foil will burn. Also chec the transformer, Chec that one of the wires did not come off the plug in the back. When you replaced the protection diode did it blow again? If not keep checking for opens on the pc board. When you said it was dead do you mean no lights at all or no tx and rx?

Jan 26, 2009 | Uniden GRANT LT 2-Way Radio

Not finding what you are looking for?
Two-Way Radios Logo

Related Topics:

839 people viewed this question

Ask a Question

Usually answered in minutes!

Top Two-Way Radios Experts

eradiostore
eradiostore

Level 3 Expert

1640 Answers

Iron
Iron

Level 3 Expert

3018 Answers

Steve

Level 3 Expert

3287 Answers

Are you a Two-Way Radio Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides

Loading...