MTS2000 - loud warbling tone on TX carrier??

[g8tzl2004]

I have a front LCD and full keypad 160 channel UHF MTS2000.

When I transmit using the side PTT and internal microphone, there is a very loud warbling tone on the TX carrier. I can just hear the required modulated audio underneath the loud warbling tone. When I place my finger on the MTS2000 case over the microphone "hole", you can then hear a hum together with the warbling tone.

BUT if I connect an external speaker mike, there is good normal TX audio coming from the external speaker mike with no warbling tone.

Is it a faulty internal mike insert? Or a dry joint on the mike insert? Any ideas?

Thanks

[g8tzl2004]

Any ideas?

[Jim202]

Any ideas?

There is a good chance what your hearing is the CTCSS. You didn't say where you were hearing this sound from. You did say that if you connected a speaker mic, the audio sounds good.

Question: Are you hearing this sound from the radio speaker while your transmitting?
............ Are you hearing this sound on another radio or scanner?

Jim

[g8tzl2004]

I am hearing the loud warbling tone while monitoring the signal on another radio.

The loud warbling tone is very much louder than any CTCSS tone.

I only get it using the internal mike...using an external speaker mike produces good nornal TX audio.

I'm thinking its an internal mike insert issue or maybe the flex cable??...but why does a faulty mike insert produce an loud tone on the TX signal. I also get an induced hum when I place my finger on the case near the internal mike insert when TXing.

[DPL]

If it goes away when you use the speaker mic, it might be RF getting into the audio.

Relevant threads:
http://batboard.batlabs.com/viewtopic.p ... 49&start=0
http://batboard.batlabs.com/viewtopic.php?t=38043

I never tried the fix on my radio so I can't confirm/deny that it works, but I think that it was a common problem with those radios.

[g8tzl2004]

Many thanks DPL - I guess it must be RF getting into the audio chain - it really is a very loud warbling tone - it blocks out any real audio from the mic.

Anybody know if the chip capacitor is solder directly on the flex cable itself or on the PCB. Where exactly do I look for the cap?

Thanks again

[g8tzl2004]

Anybody know where to look for the chip cap. I've opened the MTS2000 but I can't see any chip cap soldered to the flex but part of the flex is folded over so it might be hidden.

Anybody know how to remove the flex cable - how do you remove the mic insert from the case? Is the mic soldered to the flex? How do remove the flex from the front/case circuit board? There are a number of solder point arrange in 2 lines of about 5 solder tabs - do you unsolder these or is a plug soldered to the flex and you just pull it out?

Thanks