ghost in the MCS2000

[ryan0001]

Hi all,

Great site, lots of valuable information has been posted by fellow Moto enthusiasts.

I have a MCS2000 VHF 25W that is doing some funny things.
Around 2 months ago I was driving along when I noticed that the radio was transmitting on and off by itself.

I found out how to get into service mode (for this particular one i have to press the PTT button 5 times on start-up), worked out how to get to the button test screen and left it for a minute.
I can press buttons on the control head and the system registers it and it beeps and it's all good.

What appears to be happening is somewhere internally and for no obvious reason, it is sending a button press signal to transmit and it is doing just that.
No sound is actually broadcast when it transmits, its just dead air, however still inconvenient for all other users on the channel.

I'm guessing something has dislodged inside but it doesn't appear to be affected by vibration or movement (that is, this fault will occur whether the unit is perfectly still or bouncing up and down in the car).
Without knowing too much about the insides of these things, could anyone take a guess at what could be causing this?

Link to a YouTube video of the issue: http://youtu.be/1E8Uhn_fQKQ

[Tom in D.C.]

Isolate and test is the procedure. First thing I would test would be the microphone and cable by getting another one and seeing if that's where the trouble lies. From that point on you will probably need a circuit diagram to check point by point.

[N4KVE]

Welcome to the forum. I have several MCS2000's & I've never seen a mike like that one. What is the part number on the back of the mike? Try the process of elimination. If you don't have another mike to try, just unplug the one you have & drive around for a while. If the problem goes away, it's the mike. Good luck. GARY

[ryan0001]

Thanks for the replies guys.
The part number for the microphone is PMMN4007A.

I bought this radio about two years ago and it was operating perfectly fine, just over the last few months it's started to act up.
The fault still seems to occur whether the mic is plugged in or not.

Now not sure if this could be be contributing to the issue but there is some excess coax between the radio and antenna that has been coiled up and is very close to the radio body. Perhaps this is causing interference? Im taking the radio out of the car and reinstalling it properly this weekend so hopefully any bugs are fixed.

[N4KVE]

Coiled coax is very bad. You must unravel it. It makes SWR very high. That mike is made for the GM338, GM339, & other similar radios that aren't sold Stateside. Mind you, I see where you live, so maybe it's available there. GARY

[ryan0001]

Thanks Gary, part of the reinstall will be re-running coax and power.
Do people still repair these radios at circuit board level or are they becoming a bit obsolete?