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No mic audio

[email protected]
 

So, I just got my uBitx and have it all wired up.? It receives fine.? But, there is no transmit audio.? Here's some interesting information.? I live about 1 Km from an AM radio station putting out 25KW.? During receive, the ubitx was experiencing some intermod and I could clearly hear the local AM radio station.? When I keyed up and attempted to transmit, I could hear the ubitx key up on my TS-2000.? There was no mic audio at all.? I could see about 2 S-meter increase in noise on my TS-2000.? But, no mic audio from the ubitx.? Interestingly, the speaker audio from the local AM radio station was being transmitted by the ubitx!? It was perfectly received audio by my TS-2000.

So, I double checked all my wiring and everything on the ubitx is correct.? Orange wire from digital connector to center / ring on mic jack.? Blue from audio connector to ground.? And the purple wire from audio connector was to the tip of the mic jack.? I tried the home brew electret mic that came with the kit and also a Comet electret mic.? Still no mic audio output during transmit.

I checked everywhere I could think to check to ensure continuity.? Both the digital connector and the audio connector are wire properly.? There is a purple wire on the digital connector not used.? And, there is a red wire from the audio connector not used.

Any thoughts?

Tom - NU9R
 

Have you measured the voltage at the electret element itself?

tim ab0wr

On Mon, 14 May 2018 13:06:46 -0700
t.h.mills@... wrote:

So, I just got my uBitx and have it all wired up.? It receives fine.
But, there is no transmit audio.? Here's some interesting
information.? I live about 1 Km from an AM radio station putting out
25KW.? During receive, the ubitx was experiencing some intermod and I
could clearly hear the local AM radio station.? When I keyed up and
attempted to transmit, I could hear the ubitx key up on my TS-2000.
There was no mic audio at all.? I could see about 2 S-meter increase
in noise on my TS-2000.? But, no mic audio from the ubitx.
Interestingly, the speaker audio from the local AM radio station was
being transmitted by the ubitx!? It was perfectly received audio by
my TS-2000.

So, I double checked all my wiring and everything on the ubitx is
correct.? Orange wire from digital connector to center / ring on mic
jack.? Blue from audio connector to ground.? And the purple wire from
audio connector was to the tip of the mic jack.? I tried the home
brew electret mic that came with the kit and also a Comet electret
mic.? Still no mic audio output during transmit.

I checked everywhere I could think to check to ensure continuity.
Both the digital connector and the audio connector are wire
properly.? There is a purple wire on the digital connector not used.
And, there is a red wire from the audio connector not used.

Any thoughts?

Tom - NU9R
[email protected]
 

I get 3.0 mV to the connector with good continuity to the microphone.
Bo Barry
 

The microphone has a polarity I read. The lead connected to the case is ground.
 

You should have more than three millivolts. There is about 5K of
resistance between the TX voltage and the positive lead going to the
microphone element. With no more current than an electret pulls you
should be seeing several volts between the positive lead on the
electret and the ground on the electret (which is usually the case). If
the mic is unhooked you should be seeing full voltage on the connector,
whatever you are feeding into the ubitx, probably somewhere between
11.5v and 14v.

Three millivolts isn't enough to get much output from the electret mic.

You need to check the voltage at the mainboard (use a piece of wire
poked down into the second connector pin if necessary). If you don't
see more voltage than 3mv there then measure at the junction of C60 and
R60 to see what voltage you have.

tim ab0wr

On Mon, 14 May 2018 15:05:32 -0700
t.h.mills@... wrote:

I get 3.0 mV to the connector with good continuity to the microphone.
 

Check the mic polarity. One of the leads behind the capsule is connected to the body and that is ground

Check if there is 12v is on the mic transistor stage when you press ptt.

Raj

At 15-05-18, you wrote:

So, I double checked all my wiring and everything on the ubitx is correct. Orange wire from digital connector to center / ring on mic jack. Blue from audio connector to ground. And the purple wire from audio connector was to the tip of the mic jack. I tried the home brew electret mic that came with the kit and also a Comet electret mic. Still no mic audio output during transmit.
[email protected]
 

Yes... the microphone case is ground...? blue wire is going to ground and continuity checks good to ground everywhere as best I can tell.? Even the metal part of the microphone shows dead short to ground.? The purple lead is going to the mic side.

I measure 31 mV on both sides of R60.? I get 3 mV on one side of C60 and 31 mV on the other side of C60.? The side closest to the connector is 31 mV.? Having the mic plugged or not makes no difference.? I've measured R60 in the circuit (I know... not always reliable)... it measures 4.68 K Ohms.

There are two mods I've made but shouldn't have any effect.? I've installed a DPDT switch for 12VDC input.? And, I've installed 40mm fan on the back to keep the heat sync cool.? Should have no impact on mic audio at all.

Earlier I was getting 3 mV at the mic element.? Suspect bad meter... so, I put a different meter and I'm getting 30 mV.? Just for grins I checked the other pins on the mic... I'm getting 5VDC to the ring (PTT).? I also checked for AC just in case... no AC on any of the mic pins.
 

On TX there should be large voltage on both side of R66 if not then maybe a relay fault or faulty Q6.
Check all the voltages around Q6.

Raj

At 15-05-18, you wrote:
Yes... the microphone case is ground... blue wire is going to ground and continuity checks good to ground everywhere as best I can tell. Even the metal part of the microphone shows dead short to ground. The purple lead is going to the mic side.

I measure 31 mV on both sides of R60. I get 3 mV on one side of C60 and 31 mV on the other side of C60. The side closest to the connector is 31 mV. Having the mic plugged or not makes no difference. I've measured R60 in the circuit (I know... not always reliable)... it measures 4.68 K Ohms.

There are two mods I've made but shouldn't have any effect. I've installed a DPDT switch for 12VDC input. And, I've installed 40mm fan on the back to keep the heat sync cool. Should have no impact on mic audio at all.

Earlier I was getting 3 mV at the mic element. Suspect bad meter... so, I put a different meter and I'm getting 30 mV. Just for grins I checked the other pins on the mic... I'm getting 5VDC to the ring (PTT). I also checked for AC just in case... no AC on any of the mic pins.
[email protected]
 

During PTT I get 1.6V on the emitter, 2.2V on the base and 11V on the collector.? I'm getting supply voltage(13VDC) on one side of R66 and 12.5VDC on the side with C64.
 

The Q6 is fine.

Now that you have 12.5 on the R66 mic preamp side, you should also get that coltage on one side of R60
as they are connected together.

I suspect a bad solder or a cut track between R60/R66. Check again.

R66 @ 12V end is directly connected to R60 so you should get same voltage.

Raj

At 15-05-18, you wrote:
During PTT I get 1.6V on the emitter, 2.2V on the base and 11V on the collector. I'm getting supply voltage(13VDC) on one side of R66 and 12.5VDC on the side with C64.
[email protected]
 

PROBLEM SOLVED!

Well, actually two problems... initial problem was with voltmeter...? it was providing erroneous readings.? Once I swapped to newer voltmeter I was getting better measurements.? ?Second problem was bad solder joint at electret mic end...? ?it seems to be working now....

Thank you for your assistance.

Tom NU9R
 

Tom,

Just tug your defective meters probe wires holding the probes and do the same at the meter end.
These wires fray and probably that why you got low readings.

Raj

At 15-05-18, you wrote:
PROBLEM SOLVED!

Well, actually two problems... initial problem was with voltmeter... it was providing erroneous readings. Once I swapped to newer voltmeter I was getting better measurements. Second problem was bad solder joint at electret mic end... it seems to be working now....

Thank you for your assistance.

Tom NU9R

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