Anyone have a dead QCX with a good receiver?


K5DH
 

I'm looking for a QCX "parts unit" to hopefully repair my QCX's dead receiver.  If you have one with a live receiver but otherwise dead, please contact me via email. 

mustang_maniac@...

--

73/72,
Dean K5DH
20m QCX msn 612


ajparent1/kb1gmx
 

Why not fix the receiver?

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


George Korper
 

I believe he is looking for a unit to get the parts to do that. Am 
I missing something?

On Sat, Jan 4, 2020, 1:39 PM ajparent1/KB1GMX <kb1gmx@...> wrote:
Why not fix the receiver?

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


ajparent1/kb1gmx
 

He would be further ahead to just buy new parts.

We have no idea why to the RX is "dead" and it could be something as
basic as a bad solder joint or as catastrophic as gross over voltage or
reverse polarity.   

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


George Korper
 

No good deed should go unpunished. 


On Sat, Jan 4, 2020 at 3:36 PM ajparent1/KB1GMX <kb1gmx@...> wrote:
He would be further ahead to just buy new parts.

We have no idea why to the RX is "dead" and it could be something as
basic as a bad solder joint or as catastrophic as gross over voltage or
reverse polarity.   

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


K5DH
 

Here is a linkto the full story.  The event occurred back in 2017.  I ran across my dead QCX recently and decided to try bringing it back to life.   

https://groups.io/g/QRPLabs/topic/7431371#19203

--

73/72,
Dean K5DH
20m QCX msn 612


George Korper
 

Pity sakes, why don't you have Hans send you the chip?
I have the board here and I can send it to you but it will take as long as Hans.

From MX to USA these days,
It's like getting funds from a check while your on "Vacation": "10 working days."

That was a great full story. Especially that Q6 Pix, just send it to Hans
I would order new firmware from him and have him toss in a couple of SMD's
Without the new firmware you can end up a member of the Q6 club. 
Just put your request in the comment section and in an email getting approval before you pay.
Or put it back in the drawer and get a new one, the problem is you have to build it!


ajparent1/kb1gmx
 

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


Ward Merdes (#2457) - KL7IXW
 

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

--


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

--


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


George Korper
 

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


Andrea Massucco IZ1IVA
 

That's very interesting Vern! I have a 17m QCX whose receiver became de-sensitized and I'm still trying to find the culprit. I'd be VERY surprised if also my QCX has developed a bad C17... perhaps a faulty batch?
My QCX has order ID 12508, serial #1058, ordered on Sept. 15, 2017. Are by chance your QCX serials close to #1058?

Cheers
--
73 de Andrea IZ1IVA - cq at iz1iva . net - http://iz1iva.net


ajparent1/kb1gmx
 

Andrea,

I'd consider it unlikely that your weakened RX is C17.  Likely other failures are
to be investigated.  Oddly the first place I'd go is soldering.

From what I know literally many thousands are sold per year.  Last announcement last year
the number of units crossed 8000.  Unlikely to be in the same lot.

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


Andrea Massucco IZ1IVA
 

Il giorno 08 gen 2020, alle ore 17:52, ajparent1/KB1GMX <kb1gmx@...> ha scritto:

I'd consider it unlikely that your weakened RX is C17. Likely other failures are
to be investigated.
I agree, however Vern wrote he had to replace C17 in both his faulty QCXs… it could be a coincidence, but what are the odds of that?

Oddly the first place I'd go is soldering.
Yep, I’m reflowing a few pins at a time, but I still haven’t fixed it.

Thanks
--
73 de Andrea IZ1IVA - cq at iz1iva . net - http://iz1iva.net



--
-- 73 de Andrea IZ1IVA - cq at iz1iva . net - http://iz1iva.net


Alan G4ZFQ
 

I agree, however Vern wrote he had to replace C17 in both his faulty QCXs… it could be a coincidence, but what are the odds of that?
One could ask why no-one else has reported that problem?
I wonder what would happen if it were faulty, open or short circuit, what would be the symptoms? I'm not an expert but I think either way all that would happen is that the filter would not be so effective.

73 Alan G4ZFQ


Andrea Massucco IZ1IVA
 

Il giorno 09 gen 2020, alle ore 11:53, Alan G4ZFQ <alan4alan@...> ha scritto:

I agree, however Vern wrote he had to replace C17 in both his faulty QCXs… it could be a coincidence, but what are the odds of that?
One could ask why no-one else has reported that problem?
That’s true Alan, I’m not even trying to draw conclusions based on a sound statistical basis. However, I found it interesting that Vern found exactly the same faulty component on two QCXs and I was wondering if that could help me fixing mine.

I wonder what would happen if it were faulty, open or short circuit, what would be the symptoms? I'm not an expert but I think either way all that would happen is that the filter would not be so effective.
In my case I can barely hear signals which in reality are pretty strong, and that’s with maxed-out gain… and a quiet room HI!
I did A-B comparisons with another radio and the same antenna, I’d say signals are down a good 30+ dB. On the other hand, alignment tones are loud and clear.

My QCX was working perfectly before, only recently has developed this fault, plus the microcontroller isn’t starting anymore when first powered on (cold boot). I’m really puzzled!
--
73 de Andrea IZ1IVA - cq at iz1iva . net - http://iz1iva.net



--
-- 73 de Andrea IZ1IVA - cq at iz1iva . net - http://iz1iva.net


Alan G4ZFQ
 

I wonder what would happen if it were faulty, open or short circuit, what would be the symptoms? I'm not an expert but I think either way all that would happen is that the filter would not be so effective.
In my case I can barely hear signals which in reality are pretty strong, and that’s with maxed-out gain… and a quiet room HI!
Andrea,
I would not think that C17 would do that but maybe I'm wrong.

I did A-B comparisons with another radio and the same antenna, I’d say signals are down a good 30+ dB. On the other hand, alignment tones are loud and clear.
Are they really as strong as described in the manual? The tone signal is fed into the input of the LPF, there is not much between that and the antenna socket.

My QCX was working perfectly before, only recently has developed this fault, plus the microcontroller isn’t starting anymore when first powered on (cold boot). I’m really puzzled!
How old is it? This sort of fault was rectified very early in the life of the QCX. Look at the mods page, maybe something is faulty on one of the pins that power the micro.

73 Alan G4ZFQ


Jim Manley
 

Many thousands sold per year ... just wait until the QSX hits the street ... the total number of views for the QSX page is now over 1.1 MILLION!!!  OK, that's not views by unique visitors, and half of the views have probably been by me because I check the page every time someone mistypes QSX in a post/message, to make sure I didn't miss an announcement, but, still ... 


Jim  KJ7JHE
Lame Deer High School Amateur Radio Club  KJ7JKU


On Wed, Jan 8, 2020 at 9:52 AM ajparent1/KB1GMX <kb1gmx@...> wrote:

From what I know literally many thousands are sold per year.  Last announcement last year
the number of units crossed 8000.  Unlikely to be in the same lot.


Andrea Massucco IZ1IVA
 

Il giorno 09 gen 2020, alle ore 16:56, Alan G4ZFQ <alan4alan@...> ha scritto:

Are they really as strong as described in the manual?
They definitely are.

The tone signal is fed into the input of the LPF, there is not much between that and the antenna socket.
True, but there are many stages after that HI! I’d say the core of the receiver, the many op-amps, etc. Lots and lots of components and solder joints…
The alignment tone is strong enough to pierce whatever roadblock there is, not so real radio signals.

How old is it? This sort of fault was rectified very early in the life of the QCX. Look at the mods page, maybe something is faulty on one of the pins that power the micro.
Late 2017, but it developed this issue only very recently.

Cheers
--
73 de Andrea IZ1IVA - cq at iz1iva . net - http://iz1iva.net



--
-- 73 de Andrea IZ1IVA - cq at iz1iva . net - http://iz1iva.net