Date   
Re: QCX no BPF signal

Alan G4ZFQ
 

The 5 volt line is 5v (I tested to the right of D2 like the manual says)
IC5 pins 2 and 6 are both at 2.4v
But you said >>Both IC4 pins 7 and 9 were reading 1.7v

Which seems to me makes ">>IC5 pins 2 and 6 are both at 2.4v" very unlikely. They get their voltage from IC4 pins 7, 9.

I hope Allison comes back, your measurements make no sense to me. In the meantime check again.

73 Alan G4ZFQ

I checked C43 through C46 and R5 through R10 and they're all the correct component and no shorts.
Could it be the transformer that's causing the issues? I checked the voltages on all the primary and secondary windings and they're at the voltage they should. Is it possible that the transformer is what's causing the problems even though the voltages seem good?

Re: QCX no BPF signal

Theo
 

The 5 volt line is 5v (I tested to the right of D2 like the manual says)
IC5 pins 2 and 6 are both at 2.4v which I'm assuming is well within the acceptable range.

I checked C43 through C46 and R5 through R10 and they're all the correct component and no shorts.

Could it be the transformer that's causing the issues? I checked the voltages on all the primary and secondary windings and they're at the voltage they should. Is it possible that the transformer is what's causing the problems even though the voltages seem good?

Re: QCX no BPF signal

Alan G4ZFQ
 

If the battery is indeed 9V that should not be an issue as all of those circuits run off
regulated 5V.
Allison,

So having about 8V on IC5-10 and the rest of the 12V line will not affect voltage readings?

Both IC4 pins 7 and 9 were reading 1.7v
Is the 5 volt line actually 5V?
Are IC5 pins 2, 6 at 2.5 volts? (you say normal)
Something is not consistent.

73 Alan G4ZFQ

Re: QCX no BPF signal

ajparent1/KB1GMX
 

First you cannot meaure in circuit as devices around them will fool you.

the alternate is that you put the wrong parts in.  Either way 1.7V is just wrong!
it should be 2.5.  thats assuming that you really have 5V supply or other issues.

Also try cleaning the board with a little isopropanol and a swab as shorts
can easily hide.  Use a magnifier.

Also make sure your power source is really 9V or more, less than than
will lead to wrong measurements.

Then make sure R5 though R10 are correctly placed.  And there are
no shorts across  C43 though C46.

Allison
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Re: QCX no BPF signal

Theo
 

Both IC4 pins 7 and 9 were reading 1.7v
I checked R1 and R2 and they're both reading 5.6k ohms.
I know for a fact that they're both 10k resistors so this must mean there's a short, right?
I looked for shorts but couldn't find any, but I'm going to keep looking.

Thanks for the help.

Re: QCX no BPF signal

ajparent1/KB1GMX
 

Alan,

If the battery is indeed 9V that should not be an issue as all of those circuits run off
regulated 5V.  

Note the 9V battery should be checked to assure its actually that good.
The 5V regulator will tend to go out of regulation if the input voltage is
under 7.5V.   The average 9V rectangular alkaline battery if new is
barely enough to run the RX for more than an hour or 2 (at most)
before it sinks to about 6-7V.

Allison
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Re: QCX no BPF signal

ajparent1/KB1GMX
 

Start at IC4 the FS3253 pins 7 and 9, they must be 2.5V if not either
the wires on T1 are wrong  or R1 and R2 are wrong.  This does not
exclude the likelihood of shorts. around those as well.

If the voltages on IC5 are wrong then every one down stream
will be wrong.

Check the wiring of T1 and then all the parts around IC5, then 
proceed to check IC6 and 7, and IC8.

Most of the voltages should be around or close to 2.5V.

Allison
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50W amp connection to QCX question

Jon Reck W8REA
 

I've just finished assembling my 50W amp kit and feel pretty good about it. It is my third QRPLabs kit and I really enjoyed this one.

Now it's time to try it out and I want to get that right. As I am relatively new to this, the manual seems a little sketchy to me in this regard.

I want to connect the amp to IC3 pin 11 of the QCX. I think I have downloaded the correct pin diagram off the internet for IC3 and can find pin 11. Where is the best point to connect to? Should I solder a wire directly to the the pin from the top side of the board or is there a better way?

Similarly, I also want to do the suggested modification where I connect a 10K resister between pin 13 and pin 14 of the same IC. Again, where do you recommend I solder the resistor- directly to the two IC pins from the top side of the board?

Thanks,
Jon Reck W8REA

Re: need better eyes

K2DB Paul Mackanos
 

I had nothing to do yesterday afternoon, so I decided to wind the toroids. I have never had a problem counting turns or making the bifilar or trifiliar windings. I just clamp the end of the wires on one end with a pair of pliers, and stick the other end into a variable speed drill, and very slowly rotate it until it looks great. Your mileage may vary 😎
Paul K2DB

On Mon, Jan 6, 2020 at 10:55 AM Eric KE6US <eric.csuf@...> wrote:

I just count the turns on the inside of the toroid with my reading glasses. You could close your eyes and run a toothpick over the inside of the toroid and get an accurate count. Never have understood all the confusion about such a simple task. Nor have I understood why winding toroids is considered such a chore. Relax and enjoy the build.

Eric KE6US


Re: Anyone have a dead QCX with a good receiver?

George Korper
 

TNX Vern, I'll check C17 before my next build!

Re: Anyone have a dead QCX with a good receiver?

harleyleenuke
 

i built 5 of the qcx transceivers.  Two had low or no receive.
 I traced it down to C17  , 39nF capacitor.  
The capacitors were both bad.  I replaced them and got my receiver working awesome again.  I could hear down to -128 db.
 So maybe you have the same issue, if your lucky.

Vern
AA7HC

Re: need better eyes

Eric KE6US
 

I just count the turns on the inside of the toroid with my reading glasses. You could close your eyes and run a toothpick over the inside of the toroid and get an accurate count. Never have understood all the confusion about such a simple task. Nor have I understood why winding toroids is considered such a chore. Relax and enjoy the build.

Eric KE6US


Re: 50W PA led bending - picture and text disagree

Gregg Myers
 

The flat side of the LED goes against the board. Probably the picture is a little misleading because after the leads are bent it's hard to see what is 'shortest'. Just make sure the LED flat is against the board.

73,
Gregg

On Mon, Jan 6, 2020 at 7:08 AM Hannu OH1HAQ <oh1haq@...> wrote:
3.34. Led installation.

How should the led's be bent? If I look at the picture, the longer lead is bent right at the body...

50W PA led bending - picture and text disagree

Hannu OH1HAQ
 

3.34. Led installation.

How should the led's be bent? If I look at the picture, the longer lead is bent right at the body...

Re: Anyone have a dead QCX with a good receiver?

Roy Appleton
 

I second that, I enjoy reading Allison's post very much too!

Roy
WA0YMH

On Mon, Jan 6, 2020, 12:00 AM Ward Merdes <W.merdes@...> wrote:
01/05/20

I take a quick moment to thank Allison for yet another outstanding post. Hers are consistently the reason why I monitor this group.

Thank you, Allison. Keep up the good work.

Ward Merdes - KL7IXW
Fairbanks, Alaska 

On Sun, Jan 5, 2020 at 12:51 PM ajparent1/KB1GMX <kb1gmx@...> wrote:
Dean,

The good news is the only parts that don't like more than 3.3 or 5V are...

atmega328P micro
LCD
si5351
74ACT00
FST3251 
They are all easily had.

The opamps will tolerate 12V or more (but not reverse polarity)

With care, there is no part that should during removal damage the board.
That means often using enough heat but not a torch.  For example a I
use a .25" wide tip of an old WPT60 (old weller 60W temp controlled)
so I can heat all the leads sufficiently at the same time as it wide and
holds heat.  The other trick is building a puddle of solder to heat
them all.  The excess solder can easily be removed later.

Parts like the 5351 and FST3231 are removed with no intent to
salvage other than the board.  the flat packs the easy way is a
hot iron and a dental hook to lift the leads until its loose.  Then use 
a bit of Solderwik to clean the pads.  Some people using
solder wick "scrub " with it and that generally rips up the board.
If it doesn't wick it up when hot enough get some fresh
or maybe a better iron.  For removal a puddle of solder
across one side then heat and lift, repeat for the other.

That also means thing like fine tweezers (not junky ones)
and maybe a few repurposed dental hooks and a sharp
precision knife (EXacto). 

Generally pulling a plated though hole means you have nowhere 
near enough heat (usually the ground pin!) so things like  three
terminal regulators I cut loose and extract pins one at a time.
The parts are often are cheap, the board is not.  I've seen people
destroy a board trying to save a $0.79 part.

Once you break it for any reason the best course is a cup of
joe (or tea), a rest break, and then carefully proceeding.  its easy
to see someone over tired or distraught proceeding to compound
errors unintentionally.

I say this as I've worked on machines and radios where parts
are unobtainium and the board it self is very valuable and
hard to find even non functioning.   Proceeding carefully and
methodically is the only course. 

Recently I watched a series of videos of a few guys that are part
of the Computer history museum restoring a Apollo guidance
computer to full function (old, rare, complex, and valuable) and
during that they had to "open up" sections that were potted in
epoxy to replace a bad diode.  It takes great care, precision,
and study so that one does not create more problems.

Allison
-------------------------------
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--

Re: 50W PA 0.1uF capacitor markings / manual error

Hans Summers
 

Hi all

The 0.1uF is a "typo", it should say 1uF. I have updated the manual now. 

73 Hans G0UPL

On Sun, Jan 5, 2020 at 11:59 PM ajparent1/KB1GMX <kb1gmx@...> wrote:
However the BOM and the schematic are correct.

The statement 3.11:
These are 0.1uF 50V ceramic capacitors, code “105”.

Yes, they are 1uf and the statement is half right as 105 as the marking code.
Minor typo.

Saw that while assembling mine.  

Allison
-------------------------------
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Re: QCX no BPF signal

Alan G4ZFQ
 

Alan wrote:

Although the the voltages are a little different I do not see an obvious reason.
The obvious reason is your 9V battery! The ICs are under-run. It needs 12V

73 Alan G4ZFQ

Re: QCX no BPF signal

Alan G4ZFQ
 

The BPF signal during alignment reads 00 and the tone sounds as if it goes on and off in rapid succession and it is very quiet. I was testing the voltages of pins on the ICs and many are not in line with what the manual says they should be.
Although the the voltages are a little different I do not see an obvious reason.
(I presume they were taken using a DVM and not the one on board?)
It looks as if it might work. I do not think voltages are that far out to stop it working. Have you tried an antenna? Does it seem as if it might receive anything?
The alignment tone might be faulty rather than the receiver.

73 Alan G4ZFQ

Here are the results powered by a 9 volt
battery:
IC5
Pins 1,2,4,6,7,8 normal
Pin 3 - 1.65v
Pin 5 - 1.59v
IC6
All pins good
IC7
All pins good
IC8
Pins 3,4,5,8 good
Pin 1 - 1.32v
Pin 2 - 1.32v
Pin 6 - 1.28v
Pin 7 - 1.28v
IC9
Pins 1,2,3,4,5,8 good
Pin 6 - 1.34v
Pin 7 - 1.34v
IC10
Pins 4,8 good
Pin 1 - 3.4v
Pin 2 - 3.4v
Pin 3 - 3.4v
Pin 5 - 2.44v
Pin 6 - 2.07v
Pin 7 - 3.4v

QCX no BPF signal

Theo
 

Hey, I built my QCX about a year ago and had some trouble with the the BPF signal being 00 during alignment. I'm finally getting around to troubleshooting it so here's the information I have if anyone can help.

The BPF signal during alignment reads 00 and the tone sounds as if it goes on and off in rapid succession and it is very quiet. I was testing the voltages of pins on the ICs and many are not in line with what the manual says they should be. Here are the results powered by a 9 volt battery:

IC5
Pins 1,2,4,6,7,8 normal
Pin 3 - 1.65v
Pin 5 - 1.59v

IC6
All pins good

IC7
All pins good

IC8
Pins 3,4,5,8 good
Pin 1 - 1.32v
Pin 2 - 1.32v
Pin 6 - 1.28v 
Pin 7 - 1.28v

IC9
Pins 1,2,3,4,5,8 good
Pin 6 - 1.34v
Pin 7 - 1.34v

IC10
Pins 4,8 good
Pin 1 - 3.4v
Pin 2 - 3.4v
Pin 3 - 3.4v
Pin 5 - 2.44v
Pin 6 - 2.07v
Pin 7 - 3.4v

I'm new to building radios and such, and I'm not sure where to go from here. Any help is much appreciated.

Re: Anyone have a dead QCX with a good receiver?

Ward Merdes
 

01/05/20

I take a quick moment to thank Allison for yet another outstanding post. Hers are consistently the reason why I monitor this group.

Thank you, Allison. Keep up the good work.

Ward Merdes - KL7IXW
Fairbanks, Alaska 

On Sun, Jan 5, 2020 at 12:51 PM ajparent1/KB1GMX <kb1gmx@...> wrote:
Dean,

The good news is the only parts that don't like more than 3.3 or 5V are...

atmega328P micro
LCD
si5351
74ACT00
FST3251 
They are all easily had.

The opamps will tolerate 12V or more (but not reverse polarity)

With care, there is no part that should during removal damage the board.
That means often using enough heat but not a torch.  For example a I
use a .25" wide tip of an old WPT60 (old weller 60W temp controlled)
so I can heat all the leads sufficiently at the same time as it wide and
holds heat.  The other trick is building a puddle of solder to heat
them all.  The excess solder can easily be removed later.

Parts like the 5351 and FST3231 are removed with no intent to
salvage other than the board.  the flat packs the easy way is a
hot iron and a dental hook to lift the leads until its loose.  Then use 
a bit of Solderwik to clean the pads.  Some people using
solder wick "scrub " with it and that generally rips up the board.
If it doesn't wick it up when hot enough get some fresh
or maybe a better iron.  For removal a puddle of solder
across one side then heat and lift, repeat for the other.

That also means thing like fine tweezers (not junky ones)
and maybe a few repurposed dental hooks and a sharp
precision knife (EXacto). 

Generally pulling a plated though hole means you have nowhere 
near enough heat (usually the ground pin!) so things like  three
terminal regulators I cut loose and extract pins one at a time.
The parts are often are cheap, the board is not.  I've seen people
destroy a board trying to save a $0.79 part.

Once you break it for any reason the best course is a cup of
joe (or tea), a rest break, and then carefully proceeding.  its easy
to see someone over tired or distraught proceeding to compound
errors unintentionally.

I say this as I've worked on machines and radios where parts
are unobtainium and the board it self is very valuable and
hard to find even non functioning.   Proceeding carefully and
methodically is the only course. 

Recently I watched a series of videos of a few guys that are part
of the Computer history museum restoring a Apollo guidance
computer to full function (old, rare, complex, and valuable) and
during that they had to "open up" sections that were potted in
epoxy to replace a bad diode.  It takes great care, precision,
and study so that one does not create more problems.

Allison
-------------------------------
Please reply on list so we can share.
No direct email, it goes to bit bucket due address harvesting in groups.IO

--