Snowmobile 2 Way Radio Low Transmission

It's likely a noise cancellation issue. The little earbuds need a vent hole to sense directional (voice) vs non-directional (noise) sounds. A clogged vent muddles the sound and causes the incoming voice (microphone) and outgoing (received) sound as the noise cancelling feature tries to cancel most all noise since everything seems non-directional when the vent hole is clogged.

ZipZap, the problem is the same with or with out the in helmet speakers.

Also keep in mind the helmet speaker test (separate test) was done with a good radio that normally sends and receives perfectly.

The problem is reduced transmission output volume on any receiving radio. Its like the bad radio is putting out a signal that is not loud. Like it modulates the volume level before its sent to a good radio.

This made even figuring out the problem hard because this bad radio would receive transmissions and output them at perfect volume. I eventually figured out what was going on was that my good radios must be receiving a signal or transmission that was telling them to output a low volume level.

I dont know how this is possible because you would think the good radios would receive the transmission and just output the voice at what ever volume level the good radio are set at but whenever the good radios get a transmission from this bad radio they output a reduced volume level as if the volume on the handheld is set to 1 not 10. It even shows up when the good radio outputs its transmission to the bluetooth headphones.

I thought maybe it could be some signal transmission amplifier or something. Like the bad radio put out a weak signal but I dont know how, why or if that is even possible.

It sounds like just a bad microphone or mic preamp on the faulty one?

Or something in the transmit audio circuitry or modulator, at least.

Is it the same with a bluetooth headset that includes a microphone??

I will test that. I am not sure about the bluetooth microphone part. That would be interesting if the bluetooth microphone changed the output because it would narrow that down.

If I opened up this bad radio would it be possible to test any of those parts. I would love to fix this radio just for fun and experience.

You need to try and better pin down the problem location first - if its OK with a bluetooth mic, the modulator and RF side are likely OK, and the fault is in the analog mic circuit.

Does it have jack sockets for a hand mic / headset?

No it does not have a jack or socket.

NBD925 said:

No it does not have a jack or socket.

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OK, just a thought.
If it did have a socket, it would have allowed the mic itself vs the following audio stages to be diagnosed separately.
(And could have bee the cause of the problem).

I will do some checks when I get back into town tomorrow night.

Update:

Sorry for the delay. I was on the road with work.

I performed a few tests. The Bad Radio does work normally with a Bluetooth Microphone. It still fails when using its own microphone.

So does that mean I should be looking at the Microphone or Microphone Preamp on the Faulty radio? Any other possibilities? I will try to open the bad radio up and snap a picture of what I find.

Ok as I opened up the radio, I realized there was indeed a Headphone And Microphone Jack. It was under a rubber side cover. I didnt have my soldering kit to unsolder the antenna so I got the best shots I could under the hood.

The small Black round thing to the right of the Black and Red Speaker wires is the Microphone. Picture 3 shows a good backside visual of its placement.

NBD925 said:

The Bad Radio does work normally with a Bluetooth Microphone. It still fails when using its own microphone.

So does that mean I should be looking at the Microphone or Microphone Preamp on the Faulty radio? Any other possibilities?

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Yes, it's either the mic, the preamp - or the mic socket.

It's possible the socket is just badly tarnished and the contacts that disconnect the internal mic are not making a good connection.

Try inserting and removing a plug in the mic socket a few times, to work the contacts?

If you have a mic that fits, you can also try that - if that works, the preamp is likely to be OK and just the internal mic itself (or the socket) at fault.

I just realised that the soldered connections on the back of the mic do not look all that good - can you get more photos of that area?

It looks ok on close inspection but Who knows? I will try to find an external mic to plug in and out of the jack a few times.

Would another test be to plug in an external mic and test the radio. Would that external mic be plumed into the same Preamp as the hard wired mic?? That might narrow down the problem to a mic or the Preamp.

Where is the preamp on this board and would it be testable?

Lets say the hard wired Mic is faulty. Seems simple but I am worried about desoldering it with that super tinny resistor soldered between the + and - pins. How does one go about soldering things this small? Any special equipment?

OK, it was just the angle of the first photo, with the long leads obscuring things.

I'd expect an external mic to connect to the same preamp as the internal one, switched by the socket contacts. Trying an external mic would be helpful is possible?

The transistor circuit near the mic could be the preamp?
(I initially though the big I could include audio processing - but seeing the number, it's the LED display driver).

That white component is probably a ceramic capacitor for RF noise suppression. You should be able to use solder wick to clean up the joints and remove the mic. When refitting it, use a toothpick to hold it in place while you reflow one end.


First, though - the big surface mount module with the screening can looks to have some dubious joints. It may be worth going along those and adding a bit more solder. If one is the analog audio, a cracked joint could easily cause problems.

Hello, I dug this project back out of the box and would like to take another crack at it. Can anyone help me with what my next step should be to fix it.

I think we had narrowed it down to a bad mic or Pre Amp

NBD925 said:

It looks ok on close inspection but Who knows? I will try to find an external mic to plug in and out of the jack a few times.

Would another test be to plug in an external mic and test the radio. Would that external mic be plumed into the same Preamp as the hard wired mic?? That might narrow down the problem to a mic or the Preamp.

Where is the preamp on this board and would it be testable?

Lets say the hard wired Mic is faulty. Seems simple but I am worried about desoldering it with that super tinny resistor soldered between the + and - pins. How does one go about soldering things this small? Any special equipment?

View attachment 145225View attachment 145226

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Yes, you are gonna need special equipment. A meter and soldering iron come to mind.

I have a Meter and a Soldering Iron. I have a few other pieces of special equipment like a Digital Microscope. I should be able to fix it, if I can Purchase the correct mic or Preamp. Not sure I have fully identified the Preamp and its location.