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GP238 with Microphonics

The Rx audio circuit is working on TX. speakers mics are stopping the radio from transmitting and without the speaker mic , depress the ptt switch and tap on the case and the tapping noise comes out of the speaker . Several radiop are doing this , i changed the crystal filters and stil the same thing

Allen

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  • proff 128
    proff 128 Mar 23, 2009

    No replays
    every thing is SMD

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Sounds like a faulty or dirty relay, could be mechanical relays or solid state

Posted on Mar 07, 2009

4 Suggested Answers

Benimur
  • 6966 Answers

SOURCE: cobra 29ltd classic : no rx / tx

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

eradiostore
  • 1641 Answers

SOURCE: tone squelch

Here is a link to download the user manual for the GP68 http://safemanuals.com/user-guide-instructions-owner-manual/MOTOROLA/GP68%20RADIO%20TRANSMITTER-_E

On your first radio, the one we've been discussing, I believe you have the DPL code set incorrectly. Your radio will go up to the number 126, but this is not the DPL code's number. It is simply a numbering system.

If I read the chart correctly:
DPL 205 equals the number 072.
DPL 023 equals the number 043.

Disclaimer: This numbering system listed in the user guide does not follow any common numbering system. I have other TPL/DPL charts which differ. The above reference is only based on what I have read in the user guide.

I am confident if your radio worked previously at another job site, using other frequencies/PL codes, that your only issue at this time is programming.

As for your unlock issue on the other GP68. Your radio may be in need of repair. The internal button is possibly wornout or has been depressed too far, and is bent on the board beyond the point of functioning.

Posted on Sep 29, 2008

WV6Z
  • 7 Answers

SOURCE: FT-920: When the TUNER switch is pressed, the

Have you tired performing a general reset (see page 92 of your Operator's Manual). If you have tried this and still have had no luck, be sure that you have established a good ground to earth and that you are not getting a lot of RF back into your 920.

If you do not have a manual for your rig, one can be downloaded here http://www.download.n7tgb.net/yaesu/FT920/man_ft-920.pdf

You can also call Yaesu Tech Support for free/additional help at 714-827-7600, or join the Yahoo FT-920 User's Group at http://groups.yahoo.com/group/YaesuFT920/

Hope this helps......

Posted on Jun 26, 2009

6ya6ya
  • 2 Answers

SOURCE: I have freestanding Series 8 dishwasher. Lately during the filling cycle water hammer is occurring. How can this be resolved

Hi,
a 6ya expert can help you resolve that issue over the phone in a minute or two.
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Posted on Jan 02, 2017

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Good day I have an cobra 148 Gtl tx and rx a working but no out put


It might not seem obvious but on many, if not all, current CB radios have separate wires coming from the microphone for RX and TX. It seems like the mic wire for TRANSMIT may be open. It is a common failure.

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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.

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COBRA 21 GTL NO MODULATION NO RX. BUT IT WILL TX AT 3 WHATTS.I HAVE TRIED 3 DIFFERENT.MIC ON THIS RADIO CAN YOU HELP ME


That's usually a defective amc stage that produces RX audio and TX modulation. It's an integrated circuit that will require a tech fixing it. You will have a transmitted carrier with no modulation, and no sound in your speaker. However, make sure you have a good mike plugged in first, and substitute a known good mike to verify it's not the mike.

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I have a Cobra 18 wx st. I am not able to transmit anything on it. I have checked the antenna cables and and all external connections. I receive all the wb just fine but the CB gives me nothing. I tried a...


That's usually a defective amc stage that produces RX audio and TX modulation. It's an integrated circuit that will require a tech fixing it. You will have a transmitted carrier with no modulation, and no sound in your speaker. However, make sure you have a good mike plugged in first, and substitute a known good mike to verify it's not the mike. With the WX band working, the above may not apply.

See if you have a carrier...signal going out, but no modulation. Get your Tech to check the mike wiring/circuitry inside the radio, also.

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2 Answers

Transmitting and receiving


RF gain should be all the way up. Turn the squelch all the way down. Turn the ANL/NB to just ANL.

Turn the dynamic up at least 3/4.

Once you have confirm you can receive and transmit, then you can turn up the squelch up until white noise just stops.

Make sure you are on 19 by the highway. Key up and say break break one nine, can some one give me a radio check please.

you should get a response.

Your RF gain is how much you receive. the higher it is the more you receive. In normal operation there is no need for it ever to be less the all the way on.

Squelch is just to knock out fuzz, and if you only want to hear people close not far. A little less then half way is a basic setting.

the ANL switch is the automatic noise limiter. if you have interference from your vehicle, like engine noise, turning this on will quiet that. If it is extreme engine noise then switch it to NB, noise blanker. It is just a more intense setting.

your dynamic is how loud your audio is. if its low or all the way down, you will not transmit audio loud enough for people to hear. If its a stock radio and has not been tuned, if you turn it all the way up, that is fine.

Sep 26, 2009 | Cobra 29 LTD CB Radio

1 Answer

The mic doesnt work ...it use to but all the sudden it quit doesnt even key up so i can hear it my talk back


First, try another mic on the radio to be sure it's the mic and not the radio causing the problem. If it's the mic, check the wiring circuits for a bad switch or broken wire. Simply...the TX circuit is closed and the RX is open when the key is squeezed. The RX circuit is closed and the TX circuit is open when the key is released. Use a simple ohm meter to check for resistance between the pins on the mic (after removal from the radio of course). Open circuit will read 1, closed circuit should be very close to zero. You'll probably find the TX circuit never closes when the key is squeezed. Could be a broken wire or faulty switch in the handset.
Also check...If the mic "keys up"...you see the meter move normally, but no voice...it's either a faulty mic element (the little round thing you talk into) or the audio circuit of the radio has a defective component which a good CB shop can replace.

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1 Answer

Radio stays transmiting after mic released


What happens if you "key up" and "let off" and the transmitter "hangs", you remove the microphone plug from the Cobra ?
Will it still be transmitting or will it stop ?
If it stops, the problem is in the microphone with a "hanging" switch which you can easily clean or replace.
Iif it keeps transmitting while the mike is disconnected, there is a problem with the Rx/Tx switching circuit. This needs further investigation by use of a circuit diagram.

Feb 13, 2009 | Cobra 29 LTD CB Radio

1 Answer

Poor mic


whats the problem with your radio?
No Transmitted audio = mic cord faulty
Poor Rx / Tx power = poor SWR on the aerial
Dead radio = fuse or power supply faulty or protection diode faulty

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Cobra 148 GTL steady tone though speaker


try rerouting your coax cable and make sure it's long enough

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Road king micophone


Hi,

Most standard CB microphones are 4 wires:
Audio IN (from Mic)
Speaker
PTT (TX)
Ground.

73c90ea.jpg

To determine which is which on the radio side:
a. the Audio IN (from Mic) would read a high resistance to ground (chassis) of CB radio;
b. the Speaker when connected to the ground would activate the receive speaker. To verify, power up the radio, squelch all the way down, when shorted to ground, speaker will produce background noise/sound;
c. when PTT (TX) is shorted to the ground, the rig will transmit and the red TX indicator will light up;
d. Ground. when tested with an Ohmmeter to the chassis will read 0 ohms.

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

Good luck and kind regards.

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