Topics

V5 audio Help !


chuckr@hostu.org
 

Hi all , got my new V5 all together and all looked, good. The audio when cranked near full would about run you out of the room. So started the calibration and bfo routine and after that all seemed to work fine,So then a day or so later turned the radio on and no  audio!  Crank all the way up and you can hear but  not enough to work with, on a scale of 10 audio went from 10 to 1 or 1.5. Changed the lm386 out twice to no avail.  If anyone can direct me in the right direction or give their guess and any and all help appreciated .
thanks
chuck  73


chuckr@hostu.org
 

No audio at all now. Is there no longer any help available? Please !


Arv Evans
 

I will try to help.  Since I have not been following your specific thread, can
you bring me up to speed.  The topic indicates you are using a V5 uBITX.
What have you tried thus far?  Did it ever work?  If it once worked, what did
you do last before it stopped?  Does the tuning work (changeable frequency
display on the LCD)?  What type power supply are you using?  What is the
power supply output voltage.

Arv K7HKL
_._


On Fri, Jun 7, 2019 at 7:57 PM chuckr@... <chuckr@...> wrote:
No audio at all now. Is there no longer any help available? Please !


chuckr@hostu.org
 

Hi, as mentioned first symptoms was the sudden drop in audio to near nothing after an attempt to wire audio to the mike plug ( second round four pin connector) for digital use. All was working fine until this point , I think i may have caused the Vol-H to get grounded. I have reversed all that I was doing and all wiring etc. to where it was last working at which time the audio would adjust so loud that one would have to cover their ears. For a day or so the audio was  still barely there and you could still tune around . as time went and I tried two lm386 and now the audio is completely gone except for the low clicking of the encoder as it turns.
All i have for testing is a multi-meter. I have checked all wiring for continuity. The radio still tunes and transmits as when it was new a couple weeks ago. I know this info is lacking and not really very tech but I will try to answer / our questions etc.
Thanks much
chuck


Mike Kilpatrick <mike.kilpatrick@...>
 

I’m very new to all this but I’ve twice had the no audio except for encoder clicks. 

First time I found that I had actually lost RF input due to a faulty BNC antenna connector.  Wiggling the coax revealed this. 

The second time I don’t know what caused it but I recovered audio by reloading the V5 firmware. Sounds easy but a nightmare for me 😀

Now I can’t get the unit to retain calibration and BFO settings. 
I guess it really is educational 😀


On 8 Jun 2019, at 15:14, "chuckr@..." <chuckr@...> wrote:

Hi, as mentioned first symptoms was the sudden drop in audio to near nothing after an attempt to wire audio to the mike plug ( second round four pin connector) for digital use. All was working fine until this point , I think i may have caused the Vol-H to get grounded. I have reversed all that I was doing and all wiring etc. to where it was last working at which time the audio would adjust so loud that one would have to cover their ears. For a day or so the audio was  still barely there and you could still tune around . as time went and I tried two lm386 and now the audio is completely gone except for the low clicking of the encoder as it turns.
All i have for testing is a multi-meter. I have checked all wiring for continuity. The radio still tunes and transmits as when it was new a couple weeks ago. I know this info is lacking and not really very tech but I will try to answer / our questions etc.
Thanks much
chuck


Evan Hand
 

Without a way to measure RF it will be a challenge.  I would look into an oscilloscope, one that goes up to 100MHz as your next investment.  It can be used to measure the clock frequencies that seem to be one of the major factors in getting the uBitx to work properly.

With that being said, start by verifying all of the RX voltages (pull out the schematic to follow) at R10, R30 and R52. This should be done on both sides of the resistors to insure one of them is not fried.  Assuming that all check out, next isolate if the issue is on the audio or RF side of the rig.  I do this with a simple screwdriver (small tip) touching to the center volume control tab.  You should hear a 60 Hz (assuming US) hum through the speaker.  If this works, then the problem is upstream in either the preamp or RF/demodulater sections, and the troubleshooting becomes more difficult without some way to verify frequency.  One possible way to test sections is to take the antenna connection off and then on and see if the "noise" level changes.  You can do this on later IF stages as well by using a jumper from the antenna center wire to each of the test points starting with TP1, TP13, TP14, TP16, TP17, TP20 and TP21.  You should have a difference in noise level when touching vs not touching the TP.

If the "noise" signal injection test above verifies that all sections are working, then you most likely have a calibration issue with the BFO.  There are a number of threads on this group that can give you instructions on how to do that with both the original and other versions of firmware.  I would search for BFO calibration using the search function at the top of the page.

Try the above and report back to this group your results.  in the meantime there may be another better expert that can offer some advice.

Good Luck and Happy Hunting :-)
73
Evan
AC9TU


_Dave_ AD0B
 

If you have moved the calibration it can throw the bfo calibration off to make the audio almost disappear. Check the bfo for standard calibration. I found on one broken ubtix the bfo was about 2kc off and I couldn't hear much at all.

What are you powering the radio with?


Evan Hand
 

You can also follow this thread, as he is having the same issue.

https://groups.io/g/BITX20/topic/31971766#69562

Having been on this board for over 6 months reading every day, I can say that there is a lot of repeat calls for the same problem.  I would suggest searching the threads for your symptoms for other help as well.  Also, I know that I have got confused between threads/requests for help as to what has been tried already because there are usually more than one similar problems being reports at the same time.  Right now there are two threads with no audio active.

Please do not take this as a criticism of your actions,  The only stupid question is the one not asked.  I am trying to give you other options to get help.

FWIW
73
Evan
AC9TU


Arv Evans
 

Chuck

The VOL-High side of the volume control is probably not the culprit unless the volume
potentiometer hot side has become shorted to ground.  Temporarily shorting this to ground
would probably not damage anything. 

If you look at the circuit as a set of function blocks it should be possible to trace the problem
to its cause.  Try to avoid shotgun approaches where you jump around without a logical
approach.  If my memory is correct I think you are working on a uBITX, Version-5...?
The information on this is located at this URL:


The receive and transmit and audio mute circuit sections are described in that web page.
In this part of the circuit, The LM386 section is relatively easy to comprehend but the rest
of the circuit segment does seem to be a bit difficult to understand.  So lets take a look at
what parts perform which function.
 
ubitx_v5_audio-768x231.png

Q8 on the right is the transmit audio from microphone to BFO mixer.  This is probably not
involved in your receive audio problem.

Receive audio comes in on the right, from the BFO mixer at the common point of C63 and C50. 
It passes through C50 to the base of Q70.  Q70 amplifies this receive audio with output on the
collector and through C51.  Voltage for Q70 is provided in receive mode only via R51 and R51. 
C52 is a filtering capacitor to help isolate Q70 from extraneous signals that might be riding on
the DC power lead.

The left end of C51 is shown connected to connector pin M1.  On the main schematic points M1,
M2, M3, and M4 are shown as connected permanently to ground.  This is apparently an error in
the main diagram. 

Wiring for the volume control potentiometer is shown in URL:

ubitx_wiring.svg_-1.png

Audio output from Q70 collector goes through C51 to the HIGH side of the volume control
(VOL-H on the diagram).  This is a yellow wire from the plug on the main board.  Ground
for the volume control is on the Green wire from the plug on the main board.  Audio out
from the volume control is on the Orange wire labeled VOL-M on the drawing.

NOTE:  Q74 appears in the receive audio path but is used as an ON-OFF switch to
shunt receive audio to ground during transmit modes.  It is ON when transmitting and
an open circuit when receiving.  It is driven by T/R voltage (high in transmit mode and
ground in receive mode). 

Audio from the wiper of the volume control (VOL-M Orange wire) enters the LM386 on
input pin-3 and goes to the speaker/headphone jack from pin-5. 

Okay...you now have some detail on the receive audio path in your uBITX transceiver.
Depending on level of experience you may be able to troubleshoot the problem.  If not
please let us know and we can take the signal tracing and detection on a step-by-step
basis. 

Arv  K7HKL
_._






On Fri, Jun 7, 2019 at 11:14 PM chuckr@... <chuckr@...> wrote:
Hi, as mentioned first symptoms was the sudden drop in audio to near nothing after an attempt to wire audio to the mike plug ( second round four pin connector) for digital use. All was working fine until this point , I think i may have caused the Vol-H to get grounded. I have reversed all that I was doing and all wiring etc. to where it was last working at which time the audio would adjust so loud that one would have to cover their ears. For a day or so the audio was  still barely there and you could still tune around . as time went and I tried two lm386 and now the audio is completely gone except for the low clicking of the encoder as it turns.
All i have for testing is a multi-meter. I have checked all wiring for continuity. The radio still tunes and transmits as when it was new a couple weeks ago. I know this info is lacking and not really very tech but I will try to answer / our questions etc.
Thanks much
chuck


chuckr@hostu.org
 

Hi to all that have responded, I'am pretty sure I have found the problem, and will share the embarrassing  and simple fix if indeed this is the whole of my problem. It is late and just returned home from my grandson's wedding and tomorrow is Sunday and Church, so will be Monday before completion of my repair. Stay tuned for the tell of a funny, almost if not dumb rookie type mistake.
chuck
73 all