Topics

#v5 no #tx audio #ssb #v5 #tx

Tim Helming
 

I'm ironing out the kinks and my v5 is coming together. If I can knock this one out then I'll be ready to go out and do some operating!

My TX is good and strong on CW. Waveform seems nicely shaped (to my ear anyway, listening through my main station rig), it's bang on frequency, RX is working nicely.

But when I try to transmit on SSB, while the transmitter keys and my station rig seems to pick up the carrier, no sound comes over the mic. The TX/RX relay works fine--everything seems good, but it's as if the mic were muted or something. 

I had another mic element very similar to the one the rig shipped with. Thinking it might be a bad element, I swapped them. No difference.

I did have the mic mis-wired at first, though never with its polarity reversed or with a dead short anywhere there shouldn't have been. But is there any possibility that miswiring could have damaged the modulation circuit or something?

73,

Tim WT1IM

Reed N
 

Does RX of SSB come in well, too? Or just CW?


Reed

Evan Hand
 

Tim,
First off is the answer to Reed's question.  That will tell us if the SSB filter and the rest of the rig is aligned, as it is common for both transmit and receive. 

Another test would be to verify that the electret element is getting the bias voltage to work.  You should have somewhere between 7 and 12 volts on the positive side of the mic element (usually the tip of the 3.5 mm Mic and PPT plug).

Last that I can think of would be to verify that you are getting audio at TP20 when transmitting and speaking a loud HEEELOOOOOOOW or whistle into the mic.

So first verify that the rig BFO is aligned with the SSB filter when receiving.  Then check that the electret element is getting a bias voltage.  The last would be to verify that the mic preamp is working on TP20.

Let us know the results.

73
Evan
AC9TU

Tim Helming
 

Thanks gents

SSB receive is good. Seems to be very well on frequency, received audio is good, sensitivity seems pretty decent. I did the BFO alignment using the tool, and it came out about as expected.

But I think you've hit upon part (or all?) of the issue. I get no voltage at all to the mic. Zilch, nada, dead as a doornail. I did re-check the wiring, and there's nothing that I can see that looks amiss. I'll look at the diagrams again and see if I can figure out where that voltage is supposed to be coming from.

Tim

Evan Hand
 

Tim,
It comes from the TX voltage (only there when transmitting) through R66 (220 ohms) and R60 (4.7 K ohms) to the "audio" connector on the mainboard and then is wired to the tip connection of the 3.5 mm mic/ptt jack.

Again, it is only on when the rig is in transmit mode.

My first guess would be a wiring problem.  Verify that you do get the voltage at the audio connector and then the mic jack.  You could also check continuity from R60 to the mic element.  That could isolate if it is the wiring or the resistor.  Also, try the voltage test with the audio connector disconnected at the board connector to verify if there is a short somewhere.  With the 4.7 K resistor in series, a direct short would not release any magic smoke and could be shorting out the voltage.

The above tests are best done with a dummy load, or better yet, with the PA power removed (brown wire in the three-wire power connector).  That may be difficult with one of the AmateurRadioKits enclosures.

Good luck with your hunt!
73
Evan
AC9TU

Tim Helming
 

Thanks, Evan, I'm getting closer.

I did in fact verify that I have +12v (or so) into the mic element when PTT is held. I thought that bias was there all the time, but your explanation covers that. (I'm making these tests into a 50-ohm load so I shouldn't be hurting anything on the PA side, BTW). 

Confirmed continuity from R60 to the mic element (the ground side, hopefully that's what it's supposed to be).

Knowing that I do have voltage to the mic, should I still run the tests you suggested? Regarding the test with the audio connector disconnected--where would I measure? On the connector itself on the main board, or on the mic element? (Or to the PTT line?)

There is one other possibility here that's worth mentioning, which is that maybe my test itself was faulty. I don't think this is it, but I'll throw it out there. I tested by transmitting on the ubitx while listening on my TS-590s with no antenna connected to the Kenwood (the antenna was connected to the ubitx instead). With the TX antenna so close, though, I thought it could be possible that the Kenwood is de-sensing even with no antenna connected. I tried turning the RF gain on the Kenwood way down, but that didn't change things at all. S meter registered a carrier but no audio came through. Since I tested transmitting ubitx CW the same way and the Kenwood didn't de-sense on that test, I don't think that's the issue here. But figured I'd mention it.

-Tim

 

Tim,

I am guessing that since you say you get 12V means that the mic element is not connected.
The voltage should drop a bit when the mic is connected on TX. If what I am saying is correct
then open and check the mic element soldering. If you get 12V there and connection is fine
then replace element.

Raj

At 08/06/2020, you wrote:
Thanks, Evan, I'm getting closer.

I did in fact verify that I have +12v (or so) into the mic element when PTT is held. I thought that bias was there all the time, but your explanation covers that. (I'm making these tests into a 50-ohm load so I shouldn't be hurting anything on the PA side, BTW).

Confirmed continuity from R60 to the mic element (the ground side, hopefully that's what it's supposed to be).

Knowing that I do have voltage to the mic, should I still run the tests you suggested? Regarding the test with the audio connector disconnected--where would I measure? On the connector itself on the main board, or on the mic element? (Or to the PTT line?)

There is one other possibility here that's worth mentioning, which is that maybe my test itself was faulty. I don't think this is it, but I'll throw it out there. I tested by transmitting on the ubitx while listening on my TS-590s with no antenna connected to the Kenwood (the antenna was connected to the ubitx instead). With the TX antenna so close, though, I thought it could be possible that the Kenwood is de-sensing even with no antenna connected. I tried turning the RF gain on the Kenwood way down, but that didn't change things at all. S meter registered a carrier but no audio came through. Since I tested transmitting ubitx CW the same way and the Kenwood didn't de-sense on that test, I don't think that's the issue here. But figured I'd mention it.

-Tim

Reed N
 

Attached is the voltage measurements I get when transmitting on my v6. I think this circuit is the same as on v5, but some label numbers might be different.




Reed

Reed N
 

Oh, looks like I left out C60 in my drawing (between MIC and the 1.93V measurement), but I don't think that changes any of the results.


Reed

Bob Lunsford
 

You might also try touching the "hot" microphone lead while listening on the TS-590 while transmitting. Itt will introduce transmit noise heard on the 590 and prove that the mic audio circuit is functioning. A cheap and dirty trick from the old days of radio. Just hold a small screwdriver blade and touch the hot mic line with the PTT engaged.

On Monday, June 8, 2020, 12:35:35 AM EDT, wt1im@... <wt1im@...> wrote:


Thanks, Evan, I'm getting closer.

I did in fact verify that I have +12v (or so) into the mic element when PTT is held. I thought that bias was there all the time, but your explanation covers that. (I'm making these tests into a 50-ohm load so I shouldn't be hurting anything on the PA side, BTW). 

Confirmed continuity from R60 to the mic element (the ground side, hopefully that's what it's supposed to be).

Knowing that I do have voltage to the mic, should I still run the tests you suggested? Regarding the test with the audio connector disconnected--where would I measure? On the connector itself on the main board, or on the mic element? (Or to the PTT line?)

There is one other possibility here that's worth mentioning, which is that maybe my test itself was faulty. I don't think this is it, but I'll throw it out there. I tested by transmitting on the ubitx while listening on my TS-590s with no antenna connected to the Kenwood (the antenna was connected to the ubitx instead). With the TX antenna so close, though, I thought it could be possible that the Kenwood is de-sensing even with no antenna connected. I tried turning the RF gain on the Kenwood way down, but that didn't change things at all. S meter registered a carrier but no audio came through. Since I tested transmitting ubitx CW the same way and the Kenwood didn't de-sense on that test, I don't think that's the issue here. But figured I'd mention it.

-Tim

Evan Hand
 

Reed,
The v5 does not come with a Baofeng mic,  It is up to the builder to supply housing for the provided element and switch.  The LED, and resistor are not included, so there is not a voltage divider to drop the voltage at R60, other than the electret element.  

Tim,
There should not be continuity to the ground on the mic, It should be to the positive connection.  The mic ground should be ground.  There may be resistance to ground in the element.  I am not at my shack right now, so I cannot take the actual measurements.  I will get back to you in a little while.  In the meantime, I would double-check your wiring.

73
Evan
AC9TU

Evan Hand
 

Tim,
I got down to my shack, opened a v4 that I have (the v5 is in a more difficult case to fiddle with), and took some measurements.

1 - The resistance from the Audio connector side of R60 to the electret mic element ground was 1.89 K ohms, 0 to the positive connection of the element.
2 - I measured 11.62 volts on the element positive terminal when transmitting.  This is with 13 volts measured on the Red power wire.  I have a single diode drop on this rig because I am supplying it with a 13.8 volt Tekpower ham supply.

I have included a picture of the simple box that I put the HF Signals supplied element and switch into so you can see the wiring.  I took my measurements directly on the mic element.

I hope this helps.
73
Evan
AC9TU

Tim Helming
 

Well...you know how sometimes in the course of troubleshooting a problem either you inadvertently fix it, or realize that somehow it wasn't broken to begin with? I'm now getting TX audio as expected. 

I really have no idea what I did to change things. But I appreciate all the help. I was seriously wondering what the problem could be because on all my testing, the results I was seeing were consistent with what Evan is seeing. @Reed, thanks much for that diagram--I'm going to use that for future troubleshooting reference. @Raj, I didn't observe the same voltage drop that you did when the element was connected, but my observations do line up with @Evan's. 

I have not yet comprehensively tested (e.g. by transmitting on both USB and LSB on all bands) but will put the radio through its paces over the coming days and weeks.

My rig is a relatively stock v5, but I did make a couple mods.
  • Added the Nextion 2.4 screen
  • Fitted an onboard battery (a Bioenno 3.5Ah LiFePo) and used the DC port that the rig came with to charge the Bioenno.
  • Inside the rig the Bioenno connects to the board via a PowerPole, so I can also pop the top off and connect an external source via PowerPole if I want (though I have not made a mod to the case to allow me to close up the case. Can just put a notch in one of the panels to admit the external source's cable, I suppose.
  • The case itself is homebrewed from some copper sheet I had lying around. It doesn't look like the beautifully finished rigs I've seen in the build pics--it's kind of steampunk-ish in a way.
  • There's room in the case for a speaker but I haven't put one in yet nor cut out holes for it.

Thanks again all!

73,

Tim

Evan Hand
 

Tim,
You probably moved the wire that was shorting the mic element.

Regardless, your are welcome and glad it is working.  Now have some more fun operating!
73
Evan
AC9TU