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Re: A word of advice

Dennis AG7IN <denqrp@...>
 

Nice thread here with wise advice. Over the years, to this will add as mentioned below with familiarizing parts and learning the schematic, a free step, for someone
reading this who is about to start and excited and learning, of laying out the parts on paper taped to the bench/desk, sort them, measure them, mark the values below on
the paper, and find each part in the schematic, and this is where a beginner can learn: get to know if a part is just a pull up resistor or power filter capacitor
or in a more critical position, and are there matched sets of similar values, and will match up those measured part values and write part numbers below that, and put parts
less on value into the less critical roles. For me, that really helps to familiarize and locate missing/incorrect or out of tolerance parts and get boards working well with analog
components.

Would also suggest a board holder, they are low-cost, clean the board copper with 99% alcohol before soldering, and then clean the solder side again when done.
Adding to the great note below of a magnifier, a head mounted set with LED helps free hands, and very important, heartily agree with the posts suggesting a good temperature
controlled small iron for precision work, and small tip. For beginners to soldering, as mentioned below, practice, try a simpler kit and learn to solder well first.

--
73,
Den AG7IN


Re: A word of advice

howard winwood G4GPF
 

Oh! dear, I need to buy some more tools :-)

On 23 Jan 2021, at 19:49, David Fine <dfine100@...> wrote:

Howard, I agree with your comments, however, unfortunately by the time the new builder gets to the advice/help provided here it is often times too late.  He has already jumped in above his capabilities.  Perhaps there should be a grading scale added to the kits indicating the degree of difficulty in, not only construction of the kit, but in the difficulty of troubleshooting the kit and a list of test equipment that might be needed to do the troubleshooting if necessary.  The QCX-mini most likely cannot be troubleshot using a $5 Harbor Freight multimeter and aforementioned broken pen knife.  Dave, W0DF


Re: A word of advice

Alan G4ZFQ
 

The QCX-mini most likely cannot be troubleshot using a $5 Harbor Freight multimeter and aforementioned broken pen knife.
Dave,

Seems to me several have almost been repaired like that. A scope has been bypassed by guessing what IC(s) to replace.

73 Alan G4ZFQ


Re: A word of advice

David Fine
 

Howard, I agree with your comments, however, unfortunately by the time the new builder gets to the advice/help provided here it is often times too late.  He has already jumped in above his capabilities.  Perhaps there should be a grading scale added to the kits indicating the degree of difficulty in, not only construction of the kit, but in the difficulty of troubleshooting the kit and a list of test equipment that might be needed to do the troubleshooting if necessary.  The QCX-mini most likely cannot be troubleshot using a $5 Harbor Freight multimeter and aforementioned broken pen knife.  Dave, W0DF


Re: Help needed diagnosing newbuild QCX+

Alan G4ZFQ
 

Leo
Sorry Alan, I thought the nature of the testing and that I'd mentioned the seating of the ATmega inferred that I'd read around the problem.
Sorry, I think I got close referencing you to " it usually turns out to be OUR MISTAKE, "

73 Alan G4ZFQ


Re: Help needed diagnosing newbuild QCX+

Leo
 

Sorry Alan, I thought the nature of the testing and that I'd mentioned the seating of the ATmega inferred that I'd read around the problem. Not to worry - the link is there for others.

Thanks N3MNT - that was the second thing I checked!

Okay, it was the face palm I was looking to precipitate by posting in here.
After a mega (pun intended) magnified inspection of all of the solder joints, I noticed that one of the IC2 joints didn't appear to have a pin poking out of the top. A quick continuity check top to bottom followed by a careful inspection looking between the socket and the board revealed that one of the pins had bent over.
I pondered this for an hour or so, started to desolder then decided to try some micro surgery on the socket instead. After clearing the hole, I managed to feed a bit of offcut signal diode lead up behind the clip where I soldered it at the top of the socket. I needed to bend that pin on the IC a little to clear the now displaced clip, but it all works!

QCX+ @ 30m is functional. Now I just have to wait for the band to open which it never seems to do in the north of England.

It is a little microphonic so I'll have to open it up to check there are no overlong leads contacting the case and perhaps hot glue the coils once I've tuned the power.


Re: QCX-mini Display issue

John KG9DK
 

Ted, you came up with the solution, I remembered being concern about a short to the display "tab" so at first I tried to bend it lower, did not like that so I used side cut to cut off some the tab height.  All of that adjustment must have caused the issue you mention.   So far I have been able to remove / change the pressure at that point and I now have the correct display. 

Interesting what some small action on the builder's assembly can create a problem, when he is thinking he is fixing a problem.  I will much more respect for the metal tabs on the backside of the LCD's.

Thanks everyone's input it helped to keep me motivated.


Re: QCX-mini Display issue

Ted 2E0THH
 

Hi again John

I just dug one of these displays out of a very deep drawer.

The highlighted clips hold the whole display together, when I have messed with these in the past, problems such as yours begin to appear as the display's  internal connections misalign or fail to make proper contact.



You could first try pressing on various places on the the front of the display, if your missing line returns the try tweaking these clips.
Certainly if you tweaked them to get the display to fit in the mini, I would say look no further.

73s Ted  


Re: Help needed diagnosing newbuild QCX+

N3MNT
 


Check to make sure the connections between the front panel and the main board are correct  Looks like the connector may be misaligned.  Also check IC4 orientation.
Photos  may help.


Re: Letter 'G" next to frequency

Kyle Krafka
 

I also had this problem recently with a homemade key and a likely-mismatched antenna. I'm still experimenting, but it doesn't happen with a dummy load.


Re: QCX mini died

Dave VE3GSO
 

Perhaps a solution to using a low ESR LiPo battery is to place a low value resistance in series.  Yes, the energy loss goes against everything I believe in my bones, but it might prevent the sudden inrush currents.

Dave

On Jan 23, 2021, at 11:46, Chuck - K3FLN via groups.io <chuck.salmon@...> wrote:

Hi Fredi,
Just in case you didn't know, a fully charged 4S lipo is about 16.8 volts.  A QCX(+) would usually survive it, but not the mini.  I'm sure you will get some good help on how to proceed.
--
Cheers,
Chuck


Re: A word of advice

nz0tham@...
 

I agree and it's not elitist at all IMO.  I have built a lot of kits over the years including an Elecraft K2/100 ad I would not call the QCX series a beginners kit at all.  It's a great design and Hans has done a wonderful job of creating detailed and easy to read instruction manuals but some proven experience in building simpler kits goes a long ways when it comes to building the QCX.   I say this coming from a very non technical education (degrees in Psychology and Business) and career background.  All my electronic knowledge is solely from being a ham for 39 years.

73, Bill NZ0T


Re: Help needed diagnosing newbuild QCX+

Alan G4ZFQ
 

Naturally I have read the troubleshooting sections including the page you linked,
Leo,

OK but you did not say you looked there.
It is essential that that stage is reached. Nothing will work until you have the correct display. There must be something wrong in that little section.
Have you checked the 20MHz crystal?

I do not know how good you are but check the solder joints, one of the most frequent causes of problems.

73 Alan G4ZFQ


which is why I included a reasonably exhaustive list of
actions and measurements taken. Unfortunately the remedial actions had no effect which is why I am asking here.


Re: A word of advice

howard winwood G4GPF
 

I do hope I did not come across as elitist, it certainly was not my intension, mearly to offer some advice to newbies, to avoid too much disappointment when things don’t work.
Whilst there are lots of people who have successfully built their own equipment, I CAN assure you NOT everything works first time.
We are all fallible and can make mistakes, sometimes really stupid ones, it is just that we have built up experience in troubleshooting that allows us to dig ourselves out of the deep hole we have got ourselves in.
That is what differentiates the experts from the beginners.
Please don’t be put off, just have your eyes wide open.
best wishes to everyone

On 23 Jan 2021, at 16:06, R. Tyson via groups.io <tysons2@...> wrote:

Excellent comments. It is obvious that some people are building these kits and have poor soldering abilities, we have seen some of the photos, or little or no experience of construction. The instructions are excellent and the products are excellent. It would be better for someone with no experience to start with some simpler projects. I begin to wonder when I see questions on where to obtain components, that does not indicate any previous experience of constructing. Everyone has to start somewhere but diving straight into a complex project is not necessarily a good idea. Gaining experience on soldering and easier projects would improve the prospects of having a working radio transceiver after assembling one of these kits. Work they do when assembled correctly, are value for money and great fun to use. An experienced constructor will usually have them working first time but that comes from experience.

Reg            G4NFR


Re: QCX mini died

Chuck - K3FLN
 

Hi Fredi,
Just in case you didn't know, a fully charged 4S lipo is about 16.8 volts.  A QCX(+) would usually survive it, but not the mini.  I'm sure you will get some good help on how to proceed.
--
Cheers,
Chuck


Re: QCX mini died

howard winwood G4GPF
 

this is one problem that anyone using a lipo to power ANYTHING, is there ability to supply ridiculous amounts of energy in a very short time.
LiPo’s do not take prisoners.
Dig out the old soldering iron I guess LOL.
you have my sympathy.

On 23 Jan 2021, at 16:18, Fredi HB9BHU <hb9bhu@...> wrote:

Hi
 
I have build my QCX min 20 m Version straight foreward. Super design, super assemlby manual! It was a lot of fun to biuld it - thank you Hans!
I could carry out the alignement exactly as described in the Manual. Ecerything worked fine on my workbench an the laboratory PS; 5W out @ 13,8 V  and very sensitive RX.
But ready for the first SOTAactivation, I plugged in my Lipo 4S battery ... and bang! After first inspection I found a damaged L6 and the LM1117-5.0 has shortet the input to the output :-(!
Despite I followed the instruction to an dditional 100uF capacitor at the 12V input, I it looks like there this is not enough protection if one use a very low impedance voltage source like a LiPo battery! 
Now I afraid, I am ahead of a lot of SMD repair work. Therefore I have two questions:
1.) Has anybody experience with the repair of a dead QCX mini caused by a faild LM1117-5.0, where 13,8 V got fed into the 5 V rail? Is it a better advice to build strsight away a new kit instead of dealing with all those faied comopnents?
2.) Aside from a better regulator like 78M05, is there anything one shoud do externally to avoid high current peaks during power-up, like a coil in series?
 
73 de Fredi, HB9BHU


Re: Help needed diagnosing newbuild QCX+

Leo
 

Thanks.
Naturally I have read the troubleshooting sections including the page you linked, which is why I included a reasonably exhaustive list of actions and measurements taken. Unfortunately the remedial actions had no effect which is why I am asking here.


Re: Puff of smoke, what now?

howard winwood G4GPF
 

Ah! Puff the magic dragon, I think most of us have been there at some point.
My last one was on a self build Quadcopter, a very small ball of solder got flicked off the end of the soldering iron and landed 
on the only place on the main circuit board where it could do any damage, and it did!
The main controller + 4 esc’s all on one board, dead before I could blink.
Sometimes the gods have it in for you, bite the bullet and move on.
Hope you have not done too much damage.

On 23 Jan 2021, at 13:51, N0IIV - Rob Sullivan <rbsllvn@...> wrote:

I'm still not sure what I did wrong but I was trying to test voltage on one of the transistors. Possibly had meter in ohms, not sure. Doesn't matter. Time to move on. I haven't messed with it since the show, but I guess I'll see what I can salvage and order the rest. What is a good source for parts? 


Re: Puff of smoke, what now?

Daniel Conklin
 

Don't give up! You can get it working with a little persistence!
--
73, Dan - W2DLC


Re: Help needed diagnosing newbuild QCX+

Alan G4ZFQ
 

Leo,
Visible symptom: line of black characters at top of display.
Unfortunately you start here. http://qrp-labs.com/qcxmini/trouble.html#blank Most of the rest of your tests need to be done when the LCD is reading correctly.

73 Alan G4ZFQ


There is
the expected seashell whisper in earphones.
Checks performed: ATmega seated okay. Solder joints checked visually and by continuity from lead to pad and pad to next circuit point.