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Got my enclosure in the mail today, along with a couple of .1mf (104) caps to replace C21 and C22 to try to eliminate clicks in the keyer when I adjust the volume of the side tone. I completed the replacement (removed the old, cleaned up the area, and installed the new.? On attempting alignment this time, I have no usable audio.? When I select the BPF Peak function, I see the scale reading on the LCD, but no audio, which should be blasting from my earphones on the bench.? If I plug in an amplified speaker and turn it up to full volume, I can barely detect the tone.? I don't see how what I did could affect the audio amplifier, but that appears to be what has happened.
Suggestions, please?? The rig has been working very well up to this point. No solder bridges, whiskers, or gaps that I can see.
Thanks for help!
Tony N0BPA
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I have no usable audio.? When I select the BPF Peak function, I see the scale reading on the LCD, but no audio, which should be blasting from my earphones on the bench.? If I plug in an amplified speaker and turn it up to full volume, I can barely detect the tone.? I don't see how what I did could affect the audio amplifier, but that appears to be what has happened.
Tony, It certainly seems as if it is something you did. They are definitely 104? Try checking the voltages, maybe that will give a clue. 73 Alan G4ZFQ
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I had a similar problem, once I put the QCX in a case I lost audio.? Turned out to be the volume pot solder connections to the board.I removed the pot, placed bare wires in each of the solder points, put the pot back in and soldered the wires, board and pot terminals.? Fixed it!
KI4PSR
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On 7/28/2018 1:27 AM, Alan G4ZFQ wrote: I have no usable audio.? When I select the BPF Peak function, I see the scale reading on the LCD, but no audio, which should be blasting from my earphones on the bench. If I plug in an amplified speaker and turn it up to full volume, I can barely detect the tone.? I don't see how what I did could affect the audio amplifier, but that appears to be what has happened.
Tony,
It certainly seems as if it is something you did. They are definitely 104?
Try checking the voltages, maybe that will give a clue.
73 Alan? G4ZFQ
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I forgot to mention, when I tightened the screw holding the pc board in place, the board warped enough to undo a connection to the pot.? I could loosen the screw and get audio back.
Dave, KI4PSR
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On 7/28/2018 4:16 AM, lostfrogsrecords wrote: I had a similar problem, once I put the QCX in a case I lost audio. Turned out to be the volume pot solder connections to the board.I removed the pot, placed bare wires in each of the solder points, put the pot back in and soldered the wires, board and pot terminals.? Fixed it!
KI4PSR
On 7/28/2018 1:27 AM, Alan G4ZFQ wrote:
I have no usable audio.? When I select the BPF Peak function, I see the scale reading on the LCD, but no audio, which should be blasting from my earphones on the bench. If I plug in an amplified speaker and turn it up to full volume, I can barely detect the tone.? I don't see how what I did could affect the audio amplifier, but that appears to be what has happened.
Tony,
It certainly seems as if it is something you did. They are definitely 104?
Try checking the voltages, maybe that will give a clue.
73 Alan? G4ZFQ
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I had a volume problem too where the volume remained at full bore irrespective of the potentiometer setting. Resoldering its legs into the board fixed the problem. Even under magnified examination the original joints looked FB but obviously the wiper wasn't making electrical contact.?
On Sat., 28 Jul. 2018, 19:19 lostfrogsrecords, < dave@...> wrote: I forgot to mention, when I tightened the screw holding the pc board in
place, the board warped enough to undo a connection to the pot.? I could
loosen the screw and get audio back.
Dave, KI4PSR
On 7/28/2018 4:16 AM, lostfrogsrecords wrote:
> I had a similar problem, once I put the QCX in a case I lost audio.
> Turned out to be the volume pot solder connections to the board.I
> removed the pot, placed bare wires in each of the solder points, put
> the pot back in and soldered the wires, board and pot terminals.?
> Fixed it!
>
> KI4PSR
>
>
> On 7/28/2018 1:27 AM, Alan G4ZFQ wrote:
>>> I have no usable audio.? When I select the BPF Peak function, I see
>>> the scale reading on the LCD, but no audio, which should be blasting
>>> from my earphones on the bench. If I plug in an amplified speaker
>>> and turn it up to full volume, I can barely detect the tone.? I
>>> don't see how what I did could affect the audio amplifier, but that
>>> appears to be what has happened.
>>>
>>
>> Tony,
>>
>> It certainly seems as if it is something you did. They are definitely
>> 104?
>> Try checking the voltages, maybe that will give a clue.
>>
>> 73 Alan? G4ZFQ
>>
>>
>>
>>
>>
>>
>
>
>
>
>
>
>
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I just had the same problem with little or no audio after the change. I replaced C21 with a 1uf electrolytic and C22 with .1uf electrolytic cap. Worked fine and no chirp. Don't know if the electrolytic type capacitor made a difference but it worked. If I read the thread correctly, the original change was two .1uf then changed to two 1uf caps. I originally used two 1uf? ceramic caps- low audio. Kept C21 at 1uf and lowered C22(the main culprit I think) to .1uf.?I got a smooth key with the on-board key into a dummy load.
.
73's
Paul
KD9JYV
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Thanks, Paul (and others) – I have been leaning toward the new caps.? I have looked the board over and seen no mechanical anomalies, have checked all and reheated a few solder joints (the audio pot is not the problem, at least connection-wise. ? I will check voltages and compare to the chart.? It is a puzzlement to me.? Of course, I can’t rule out air-headity in this situation, either. ? 73, Tony N0BPA ? ?
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From: [email protected] [mailto:[email protected]] On Behalf Of paul wegwert
Sent: Saturday, July 28, 2018 12:35 PM
To: [email protected]
Subject: Re: [QRPLabs] QCX 40 Lost audio ? I just had the same problem with little or no audio after the change. I replaced C21 with a 1uf electrolytic and C22 with .1uf electrolytic cap. Worked fine and no chirp. Don't know if the electrolytic type capacitor made a difference but it worked. If I read the thread correctly, the original change was two .1uf then changed to two 1uf caps. I originally used two 1uf? ceramic caps- low audio. Kept C21 at 1uf and lowered C22(the main culprit I think) to .1uf.?I got a smooth key with the on-board key into a dummy load.
.
73's
Paul
KD9JYV
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Here I am replying to my own message.? Not sure how else to continue this thread.
I measured voltages according to the chart in the QCX manual, and what I found is in the table that follows.? I assumed that a variance of 5% probably was acceptable, especially with my supply voltage being slightly higher; marked everything else in red.
I will appreciate any more help in getting this resolved so that I can get back on the air.
73 to all,
Tony N0BPA
|
Here I am replying to my own message.? Not sure how else to continue this thread.
Tony, I see no problem, in some groups it might be an etiquette thing but as you say it's the only way to keep going, and maybe correct or add something. I measured voltages according to the chart in the QCX manual, and what I found is in the table that follows.? I assumed that a variance of 5% probably was acceptable, especially with my supply voltage being slightly higher; marked everything else in red. Nice the spreadsheet might help others to tabulate results. I'd say 10% or more difference, certainly at some points. Like IC6,7. Their outputs, both pin 1, are correct so I'm ignoring all before that. IC8 pin 5..... Results after that seem to suggest that the values in the manual are tested using the low impedance internal voltmeter. When just looking at things I've puzzled over these chart voltages before. You must have used a proper high input resistance one? If so I'm not sure I see anything wrong. 73 Alan G4ZFQ
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Hi, Tony
Let's start with IC8. It is wired as 2 voltage followers, so the
voltages on pins 3 and 5 are actually the the same as the voltages
on pins 1 and 7. The low voltage reading is a measurement error
caused by a low impedance voltmeter pulling down a high impedance
source. Since pins 1 and 7 are about normal there's no dc problem
here.
So - let's try "divide and conquer". Set the keyer for code
practice and hit the key. If you get a tone in your 'phones' the
entire audio chain is working - it's a receiver problem. No
sidetone? Take a screwdriver, set the volume for 50%, hold the
screwdriver blade in your hand and touch it to the center volume
control connection. If you get a buzz the audio amp is OK. No
buzz? Either it's muted (Q7 turned on), or there's an actual audio
output problem. That's a start. Let us know what you find.
Jim Daldry W4JED
On 07/29/2018 02:51 AM, Tony McUmber
wrote:
toggle quoted message
Show quoted text
Here I am replying
to my own message.? Not sure how else to continue this thread.
I measured voltages according to the chart in the QCX manual, and
what I found is in the table that follows.? I assumed that a
variance of 5% probably was acceptable, especially with my supply
voltage being slightly higher; marked everything else in red.
I will appreciate any more help in getting this resolved so that I
can get back on the air.
73 to all,
Tony N0BPA
|
Fwiw:? I used a digital VOM for all the measurements.? I can detect a tone, but it is so extremely weak that I must use an amplified speaker even to hear a hint of it; it should be blasting my earphones off the bench when I select the BPF in the alignment process, even with the volume pot turned completely CCW (which it did when I did the initial alignment). ? The alignment metering information appears on the display as it should for the BPF audio, then the IQ Bal, Phase LO, and Phase Hi in turn; I just can’t hear it. ? The voltages around IC8 and IC9 are all within shouting distance of the nominal value, except pins 3 and 5 on each, which are >70% over voltage. ? I am not an expert (which is why I am asking for help here), but I would think that would indicate a fault in this part of the circuit or else another circuit that is feeding it. ? Perhaps I am way off base here. ? I can re-send the voltage chart if that will help. ? 73, Tony N0BPA
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From: [email protected] [mailto:[email protected]] On Behalf Of James Daldry W4JED
Sent: Sunday, July 29, 2018 9:59 AM
To: [email protected]
Subject: Re: [QRPLabs] QCX 40 Lost audio? Hi, Tony Let's start with IC8. It is wired as 2 voltage followers, so the voltages on pins 3 and 5 are actually the the same as the voltages on pins 1 and 7. The low voltage reading is a measurement error caused by a low impedance voltmeter pulling down a high impedance source. Since pins 1 and 7 are about normal there's no dc problem here. So - let's try "divide and conquer". Set the keyer for code practice and hit the key. If you get a tone in your 'phones' the entire audio chain is working - it's a receiver problem. No sidetone? Take a screwdriver, set the volume for 50%, hold the screwdriver blade in your hand and touch it to the center volume control connection. If you get a buzz the audio amp is OK. No buzz? Either it's muted (Q7 turned on), or there's an actual audio output problem. That's a start. Let us know what you find. Jim Daldry W4JED On 07/29/2018 02:51 AM, Tony McUmber wrote: Here I am replying to my own message.? Not sure how else to continue this thread.
I measured voltages according to the chart in the QCX manual, and what I found is in the table that follows.? I assumed that a variance of 5% probably was acceptable, especially with my supply voltage being slightly higher; marked everything else in red.
I will appreciate any more help in getting this resolved so that I can get back on the air.
73 to all,
Tony N0BPA
?
|
Fwiw:? I used a digital VOM for all the measurements. Tony, It is worth a lot. Section 6.4:- "DC voltage readings The following table lists the DC voltage read at various points around the circuit. This may aid troubleshooting. The voltage measurements were made using the in-built DVM, in menu item 9.1. The voltages around IC8 and IC9 are all within shouting distance of the nominal value, except pins 3 and 5 on each, which are >70% over voltage.
Use the in-built DVM. This loads the circuit giving the readings shown on the chart. The chart really needs another column giving readings made by a "proper" high impedance meter. Sorry I can't help with your problem other than say do the tests Jim has advised. 73 Alan G4ZFQ
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I am attaching a revised voltage chart.? The measurements have not changed, but I have changed the way the percentages are displayed to reflect properly the percentage difference between the measured value and the nominal value rather than vice-versa.? I have highlighted in red percentage changes that seem extreme.? I hope this will be more useful to anyone interested. ? 73, Tony N0BPA ? ?
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From: [email protected] [mailto:[email protected]] On Behalf Of Tony McUmber
Sent: Sunday, July 29, 2018 6:09 PM
To: [email protected]
Subject: Re: [QRPLabs] QCX 40 Lost audio? Fwiw:? I used a digital VOM for all the measurements.? I can detect a tone, but it is so extremely weak that I must use an amplified speaker even to hear a hint of it; it should be blasting my earphones off the bench when I select the BPF in the alignment process, even with the volume pot turned completely CCW (which it did when I did the initial alignment). ? The alignment metering information appears on the display as it should for the BPF audio, then the IQ Bal, Phase LO, and Phase Hi in turn; I just can’t hear it. ? The voltages around IC8 and IC9 are all within shouting distance of the nominal value, except pins 3 and 5 on each, which are >70% over voltage. ? I am not an expert (which is why I am asking for help here), but I would think that would indicate a fault in this part of the circuit or else another circuit that is feeding it. ? Perhaps I am way off base here. ? I can re-send the voltage chart if that will help. ? 73, Tony N0BPA ? Hi, Tony Let's start with IC8. It is wired as 2 voltage followers, so the voltages on pins 3 and 5 are actually the the same as the voltages on pins 1 and 7. The low voltage reading is a measurement error caused by a low impedance voltmeter pulling down a high impedance source. Since pins 1 and 7 are about normal there's no dc problem here. So - let's try "divide and conquer". Set the keyer for code practice and hit the key. If you get a tone in your 'phones' the entire audio chain is working - it's a receiver problem. No sidetone? Take a screwdriver, set the volume for 50%, hold the screwdriver blade in your hand and touch it to the center volume control connection. If you get a buzz the audio amp is OK. No buzz? Either it's muted (Q7 turned on), or there's an actual audio output problem. That's a start. Let us know what you find. Jim Daldry W4JED On 07/29/2018 02:51 AM, Tony McUmber wrote: Here I am replying to my own message.? Not sure how else to continue this thread.
I measured voltages according to the chart in the QCX manual, and what I found is in the table that follows.? I assumed that a variance of 5% probably was acceptable, especially with my supply voltage being slightly higher; marked everything else in red.
I will appreciate any more help in getting this resolved so that I can get back on the air.
73 to all,
Tony N0BPA
?
|
I sent this revised chart before I saw the note from ALAN G4ZFQ.? I will re-measure with the built-in DVM as soon as I figure out how to operate it. ? Tony N0BPA ? ?
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From: [email protected] [mailto:[email protected]] On Behalf Of Tony McUmber
Sent: Monday, July 30, 2018 1:45 AM
To: [email protected]
Subject: Re: [QRPLabs] QCX 40 Lost audio? I am attaching a revised voltage chart.? The measurements have not changed, but I have changed the way the percentages are displayed to reflect properly the percentage difference between the measured value and the nominal value rather than vice-versa.? I have highlighted in red percentage changes that seem extreme.? I hope this will be more useful to anyone interested. ? 73, Tony N0BPA ? ? ? Fwiw:? I used a digital VOM for all the measurements.? I can detect a tone, but it is so extremely weak that I must use an amplified speaker even to hear a hint of it; it should be blasting my earphones off the bench when I select the BPF in the alignment process, even with the volume pot turned completely CCW (which it did when I did the initial alignment). ? The alignment metering information appears on the display as it should for the BPF audio, then the IQ Bal, Phase LO, and Phase Hi in turn; I just can’t hear it. ? The voltages around IC8 and IC9 are all within shouting distance of the nominal value, except pins 3 and 5 on each, which are >70% over voltage. ? I am not an expert (which is why I am asking for help here), but I would think that would indicate a fault in this part of the circuit or else another circuit that is feeding it. ? Perhaps I am way off base here. ? I can re-send the voltage chart if that will help. ? 73, Tony N0BPA ? Hi, Tony Let's start with IC8. It is wired as 2 voltage followers, so the voltages on pins 3 and 5 are actually the the same as the voltages on pins 1 and 7. The low voltage reading is a measurement error caused by a low impedance voltmeter pulling down a high impedance source. Since pins 1 and 7 are about normal there's no dc problem here. So - let's try "divide and conquer". Set the keyer for code practice and hit the key. If you get a tone in your 'phones' the entire audio chain is working - it's a receiver problem. No sidetone? Take a screwdriver, set the volume for 50%, hold the screwdriver blade in your hand and touch it to the center volume control connection. If you get a buzz the audio amp is OK. No buzz? Either it's muted (Q7 turned on), or there's an actual audio output problem. That's a start. Let us know what you find. Jim Daldry W4JED On 07/29/2018 02:51 AM, Tony McUmber wrote: Here I am replying to my own message.? Not sure how else to continue this thread.
I measured voltages according to the chart in the QCX manual, and what I found is in the table that follows.? I assumed that a variance of 5% probably was acceptable, especially with my supply voltage being slightly higher; marked everything else in red.
I will appreciate any more help in getting this resolved so that I can get back on the air.
73 to all,
Tony N0BPA
?
|
Hi, Tony
If the voltmeter has a high enough input impedance that it didn't
load down pins 3 and 5, then IC8 is hosed. Replace it with any
reasonably decent dual op amp - TL072, TL082, 4558, etc. Again,
this is assuming YOUR DVM has a high enough input impedance. Some
of the cheapies have a pretty low input impedance on the low
voltage ranges.
The allignment tone tests the entire receiver. The cw sidetone,
when you press the key, tests the sideband filter, the cw audio
filter, and the audio amp. The screwdriver buzz on the volume
control tests just the audio amp. If you don't get the buzz,
forget about IC8 - you still should get the buzz with no IC8 in
the circuit.
Volume control wiring on these boards has been a constant
bugaboo, because the volume pins don't quite reach the board. If
either the high or the center pins of the volume control are not
making contact with the board, you will have weak or no audio. The
instructions should have had you add a short piece of wire to each
volume lug before installing the control.
If the gate (middle pin) of Q7 has over about a volt on it, it
will kill the audio. It should be zero.
If you try the cw sidetone test, first set the menu to 4.7 code
practice. If I'm listening to W1AW code lessons I leave my rig on
code practice so I can tap the key to reset the decoder - mine
tends to start writing gibberish after a minute or 2.
Jim Daldry
On 07/29/2018 07:09 PM, Tony McUmber
wrote:
toggle quoted message
Show quoted text
Fwiw:? I used a digital VOM for all
the measurements.? I can detect a tone, but it is so
extremely weak that I must use an amplified speaker even to
hear a hint of it; it should be blasting my earphones off
the bench when I select the BPF in the alignment process,
even with the volume pot turned completely CCW (which it did
when I did the initial alignment).
?
The alignment metering information
appears on the display as it should for the BPF audio, then
the IQ Bal, Phase LO, and Phase Hi in turn; I just can’t
hear it.
?
The voltages around IC8 and IC9 are
all within shouting distance of the nominal value, except
pins 3 and 5 on each, which are >70% over voltage.
?
I am not an expert (which is why I am
asking for help here), but I would think that would indicate
a fault in this part of the circuit or else another circuit
that is feeding it.
?
Perhaps I am way off base here.
?
I can re-send the voltage chart if
that will help.
?
73, Tony N0BPA
?
Hi, Tony
Let's start with IC8. It is wired as 2 voltage followers, so
the voltages on pins 3 and 5 are actually the the same as the
voltages on pins 1 and 7. The low voltage reading is a
measurement error caused by a low impedance voltmeter pulling
down a high impedance source. Since pins 1 and 7 are about
normal there's no dc problem here.
So - let's try "divide and conquer". Set the keyer for code
practice and hit the key. If you get a tone in your 'phones'
the entire audio chain is working - it's a receiver problem.
No sidetone? Take a screwdriver, set the volume for 50%, hold
the screwdriver blade in your hand and touch it to the center
volume control connection. If you get a buzz the audio amp is
OK. No buzz? Either it's muted (Q7 turned on), or there's an
actual audio output problem. That's a start. Let us know what
you find.
Jim Daldry W4JED
On 07/29/2018 02:51 AM, Tony McUmber
wrote:
Here I am replying to my own message.?
Not sure how else to continue this thread.
I measured voltages according to the chart in the QCX
manual, and what I found is in the table that follows.? I
assumed that a variance of 5% probably was acceptable,
especially with my supply voltage being slightly higher;
marked everything else in red.
I will appreciate any more help in getting this resolved so
that I can get back on the air.
73 to all,
Tony N0BPA
?
|
I have measured the voltages with the internal meter to be more consistent with the data.? There are some glaring differences! Here is my new, revised chart.? I have highlighted differences over 10%.? I hope this is helpful to any with an interest.? I look forward to solving my no-audio dilemma. ? Thanks, all! Tony N0BPA ? ?
toggle quoted message
Show quoted text
From: [email protected] [mailto:[email protected]] On Behalf Of Tony McUmber
Sent: Monday, July 30, 2018 1:51 AM
To: [email protected]
Subject: Re: [QRPLabs] QCX 40 Lost audio? I sent this revised chart before I saw the note from ALAN G4ZFQ.? I will re-measure with the built-in DVM as soon as I figure out how to operate it. ? Tony N0BPA ? ? ? I am attaching a revised voltage chart.? The measurements have not changed, but I have changed the way the percentages are displayed to reflect properly the percentage difference between the measured value and the nominal value rather than vice-versa.? I have highlighted in red percentage changes that seem extreme.? I hope this will be more useful to anyone interested. ? 73, Tony N0BPA ? ? ? Fwiw:? I used a digital VOM for all the measurements.? I can detect a tone, but it is so extremely weak that I must use an amplified speaker even to hear a hint of it; it should be blasting my earphones off the bench when I select the BPF in the alignment process, even with the volume pot turned completely CCW (which it did when I did the initial alignment). ? The alignment metering information appears on the display as it should for the BPF audio, then the IQ Bal, Phase LO, and Phase Hi in turn; I just can’t hear it. ? The voltages around IC8 and IC9 are all within shouting distance of the nominal value, except pins 3 and 5 on each, which are >70% over voltage. ? I am not an expert (which is why I am asking for help here), but I would think that would indicate a fault in this part of the circuit or else another circuit that is feeding it. ? Perhaps I am way off base here. ? I can re-send the voltage chart if that will help. ? 73, Tony N0BPA ? Hi, Tony Let's start with IC8. It is wired as 2 voltage followers, so the voltages on pins 3 and 5 are actually the the same as the voltages on pins 1 and 7. The low voltage reading is a measurement error caused by a low impedance voltmeter pulling down a high impedance source. Since pins 1 and 7 are about normal there's no dc problem here. So - let's try "divide and conquer". Set the keyer for code practice and hit the key. If you get a tone in your 'phones' the entire audio chain is working - it's a receiver problem. No sidetone? Take a screwdriver, set the volume for 50%, hold the screwdriver blade in your hand and touch it to the center volume control connection. If you get a buzz the audio amp is OK. No buzz? Either it's muted (Q7 turned on), or there's an actual audio output problem. That's a start. Let us know what you find. Jim Daldry W4JED On 07/29/2018 02:51 AM, Tony McUmber wrote: Here I am replying to my own message.? Not sure how else to continue this thread.
I measured voltages according to the chart in the QCX manual, and what I found is in the table that follows.? I assumed that a variance of 5% probably was acceptable, especially with my supply voltage being slightly higher; marked everything else in red.
I will appreciate any more help in getting this resolved so that I can get back on the air.
73 to all,
Tony N0BPA
?
|
If the voltmeter has a high enough input impedance that it didn't load down pins 3 and 5, then IC8 is hosed Jim, Why do you say that? The readings on the chart in the QRP Labs manual are made with the low impedance internal meter. Tony, using a high impedance DVM said "The voltages around IC8 and IC9 are all within shouting distance of the nominal value, except pins 3 and 5 on each, which are >70% over voltage." These higher impedance points will all be dragged down by the internal meter as shown on the QRP Labs chart. A high impedance meter will give the true voltages which is what Tony is measuring. 73 Alan G4ZFQ
|
Here is my new, revised chart. Tony, I do not see it. 73 Alan G4ZFQ
|
|
|
I have measured the voltages with the internal meter to be more consistent with the data.? There are some glaring differences!
Here is my new, revised chart.? I have highlighted differences over 10%. Tony That now shows IC8/9 are as expected. In similar RXs I've known C45, 46 voltages to vary according to tuned frequency. This will make IC5-5 differ. IC6-3 probably depends on the position of R24. And IC6-5 on R17. I do not think there is anything to worry about, in any case the audio chips are correct. Get that right first. Do Jim's signal tracing with a pin held in your hand. IC10-6&7. 73 Alan G4ZFQ
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James Daldry W4JED