Date   

Re: New (was working fine) QCX+ 20 making loud buzzing, motorbike and clock audio after editing functions.

 

Absolutely: the output circuit is just a signal level op-amp, not a formal transducer driver, so the impedance of your headset should be at least 100 ohms or so. I haven't looked recently, but the spec on the website probably says something about this...
Adding a bit more info, the op-amp is operating in a unity gain configuration, with the output folded directly back to the inverting input, meaning that if you pull the output down hard, you're also pulling down the inverting input of a very high gain amplifier, without allowing the output to respond, and it won't take kindly to that at all.
--
Julian, N4JO.


Thermal Resistance, Junction to Ambient BS-170

Shawn Reed
 

And then, there is junction to case. Just some factors involved with the BS-170 failing. Not that I have experienced this, I am just a builder, at home. Non-operator. I was thinking about SOTA and the altitudes reached. As a youngster, I backpacked aplenty in the Sierra's, out of Bishop, Calif. Trailheads usually started around 8,000 ft. On to the higher chain of lakes where golden trout can be found, and or caught. This is at 10,000 ft and above. Might I add, 7x tippit leader is needed along with a 22 size midge, for success. I degress. So, At 8,000 ft ele. you have less air pressure and higher temp. ....


https://www.allaboutcircuits.com/technical-articles/junction-to-ambient-thermal-resistance-ic-package-thermal-performance/

........."There are several other factors that can affect the junction-to-ambient thermal resistance. For example, thermal resistance increases with altitude. A device operating at 8000 ft experiences smaller air pressure and can run 20% hotter compared to the same device operating at sea level. Interestingly, major system design companies employ pressure chambers to test the thermal performance of their design at different altitudes.

Thermal resistance is also a function of the ambient temperature. A 20% reduction in the overall θJA can occur by going from an ambient temperature of 0 °C to 100 °C. Additionally, θJA decreases as the power dissipated in a given IC increases".

I look to the homemade solution, if one is needed. thank you, 73, sreed. kf7yff.


Re: New (was working fine) QCX+ 20 making loud buzzing, motorbike and clock audio after editing functions.

Ron Carr
 

I seem to remember a motorboating issue if the headphones used are too low in impedance.  Or was that a different radio?


Re: New (was working fine) QCX+ 20 making loud buzzing, motorbike and clock audio after editing functions.

tony.volpe.1951@...
 

Thanks for the suggestion Terry, but the same power supply functions perfectly with my classic CQX and my CQX+ 40. In case you are suspecting RF feedback getting in on input lines, the problem happens without ever keying the TX. The issue is editing functions only, using the front panel buttons.  I can have a cw qso and no issues arise. 


Re: New (was working fine) QCX+ 20 making loud buzzing, motorbike and clock audio after editing functions.

terry schulz
 

Km6kje try putting a ferrite ring on the power cord for an easy start??

On Thursday, December 9, 2021, 07:35:07 AM PST, tony.volpe.1951@... <tony.volpe.1951@...> wrote:


I just got my QRPlabs factory built QCX+20 last week. Worked beautifully for a few days of WSPR and CW. All perfect. Delighted. Big grins.
 
Now all of a sudden, with no known accidents, it has started behaving very oddly.

On switch on, the rig works fine; sensitive receive and faultless transmit. Power normal. 

But then, on entering the edit menus, things started to go wrong. If for example setting time in beacon mode, I can edit the hour digits, but on clicking to enter the minute digits, a loud buzz comes into the headphones. This buzz can turn into a motorbike rapid popping sound as you come out of the menus and it changes volume and frequency as I press the menu editing buttons. Different menu setting modes can result in different amplitude of buzz or tone frequency. The only way to end this annoyance is to power cycle the radio. Then it comes back fine, until you start to edit any parameter and at some point in the editing process, it returns. The onset of the problem is not systematic, it can happen early or late in the edit process, always, I think, as I press the right button to leave a particular menu.

My first line of attack, was to do a factory reset. Forgot I had the TXO and the rig came back with a system frequency of 27MHZ, which for a time lost me my receive, until I figured out the issue and corrected it, but the Buzzing problem was still there.

Reluctantly, I opened the case and examined the board with a jeweller's loupe. I found a couple of dark, 'slaggy' looking, flux deposits on joints and removed them, along with a few small, 1mm sized, solder flakes, which might have made mischief  either now or later. I checked the seating of the AVR, raised it slightly and then re-seated it. The problem was still there on re-assembling the front panel

If I power the set down and reboot. It works normally until I need to change something in the menus.

It can also be brought on by unplugging the key or plugging it. My well used QCX+ 40 does not object to this.

EDIT:

I have removed and re-seated the front panel a couple of times and have found a change in behaviour. There may be an issue in the seating of the panel or the pins, perhaps a dry joint - don't know yet. I have managed to operate the rig menu features a few times without the fault. This persisted until I wiggled the front panel and then it returned. 

I will investigate further. Maybe there is an issue with the front panel and an intermittent connection issue. I don't have time right now to investigate, but in the meantime, If anyone has a clue what might be causing this, I'd appreciate their input. 

Thanks

Tony G0BZB


Re: QDX #40m #qdx #manual RFSweep waveform different to manual #qdx #manual #40m

Mark ZS6MDX
 

Thanks Alan, much appreciated, will check these on the weekend and hope that sorts it out... A great build otherwise!


On Thu, Dec 9, 2021 at 9:56 AM Alan G4ZFQ <alan4alan@...> wrote:
> QDX is built and firmware loaded, on dummyload the RF Filter sweep (top)
> looks quite different than the example in the manual (v 1.06 page 89)  -

  Mark,

Assuming v 1.02 is loaded then maybe something in the BPF or LPF.

Do you have TX power on all bands? If not any band maybe LPF switching
or bad joint in common path.

The RF sweep checks LPF and BPF so if TX is good then maybe a bad joint
on L12.

73 Alan G4ZFQ








--
Mark Walker
+2782 385 2688


New (was working fine) QCX+ 20 making loud buzzing, motorbike and clock audio after editing functions.

tony.volpe.1951@...
 

I just got my QRPlabs factory built QCX+20 last week. Worked beautifully for a few days of WSPR and CW. All perfect. Delighted. Big grins.
 
Now all of a sudden, with no known accidents, it has started behaving very oddly.

On switch on, the rig works fine; sensitive receive and faultless transmit. Power normal. 

But then, on entering the edit menus, things started to go wrong. If for example setting time in beacon mode, I can edit the hour digits, but on clicking to enter the minute digits, a loud buzz comes into the headphones. This buzz can turn into a motorbike rapid popping sound as you come out of the menus and it changes volume and frequency as I press the menu editing buttons. Different menu setting modes can result in different amplitude of buzz or tone frequency. The only way to end this annoyance is to power cycle the radio. Then it comes back fine, until you start to edit any parameter and at some point in the editing process, it returns. The onset of the problem is not systematic, it can happen early or late in the edit process, always, I think, as I press the right button to leave a particular menu.

My first line of attack, was to do a factory reset. Forgot I had the TXO and the rig came back with a system frequency of 27MHZ, which for a time lost me my receive, until I figured out the issue and corrected it, but the Buzzing problem was still there.

Reluctantly, I opened the case and examined the board with a jeweller's loupe. I found a couple of dark, 'slaggy' looking, flux deposits on joints and removed them, along with a few small, 1mm sized, solder flakes, which might have made mischief  either now or later. I checked the seating of the AVR, raised it slightly and then re-seated it. The problem was still there on re-assembling the front panel

If I power the set down and reboot. It works normally until I need to change something in the menus.

It can also be brought on by unplugging the key or plugging it. My well used QCX+ 40 does not object to this.

EDIT:

I have removed and re-seated the front panel a couple of times and have found a change in behaviour. There may be an issue in the seating of the panel or the pins, perhaps a dry joint - don't know yet. I have managed to operate the rig menu features a few times without the fault. This persisted until I wiggled the front panel and then it returned. 

I will investigate further. Maybe there is an issue with the front panel and an intermittent connection issue. I don't have time right now to investigate, but in the meantime, If anyone has a clue what might be causing this, I'd appreciate their input. 

Thanks

Tony G0BZB


Re: QCX Mini 40M smoked #qcxmini #rip

Paul Christensen
 

To me, it seems dangerous to bring active circuit voltages (i.e., PTT jack) directly to the outside world without some form of buffering.  Even some amount of series R often helps. 

 

Has anyone added a logic converter/buffer in front of the PTT jack to simply “ground on TX?”  For example, a 10K resistor from the TX line to the (G)ate of a SMD 2N7000 (or equiv.) provides a Vdss max open key line voltage of 60 VDC.  Max current = 200 mA that will safely key any modern external amplifier.  2N7000 (S)ource to circuit GND, (D)rain to the PTT jack “tip.”   I know someone recently made a post about a mod to the QRP Labs 50W amp, but IMHO the mod really belongs inside the QCX Mini. 

 

It may be possible to Dremel the trace around the PTT jack and solder the 2N7000 (D)rain to the tip lead.  This forms the mounting of the 2N7000 right at the PTT jack.   Short Kynar wire to the other leads. 

 

Perhaps the next QCX Mini board revision can include the two parts? 

 

Paul, W9AC       

 

From: QRPLabs@groups.io <QRPLabs@groups.io> On Behalf Of Steve Greffe - VE3SGV
Sent: Thursday, December 9, 2021 8:57 AM
To: QRPLabs@groups.io
Subject: Re: [QRPLabs] QCX Mini 40M smoked #qcxmini #rip

 

Yup, shorting out the PTT line claimed my 80M Mini too.
But for me it was hot plugging the PTT to the companion 50W amp. Toasted the Ver. 1 regulator and pretty much everything else on the board that was black and had more than two leads. I'm not equipped to do SMD so it was most economical to start over with a new kit, minus the case. Live and learn as they say. Sorry to hear of the magic smoke experiment you had, but don't feel bad--it's easily done and we're not the first.

73
Steve VE3SGV 


Re: QDX 40m Receive/transmit Issue

Zachary Painter
 

I'll check this too!


Re: QDX 40m Receive/transmit Issue

Zachary Painter
 

Ronald, thanks! I will look into it when I get home!


Re: QCX Mini 40M smoked #qcxmini #rip

Daniel Conklin
 

I covered mine with black gaffer's tape, but here is a link to a 3D printed plug: https://youtu.be/TMTnHdHTC4M


On Wed, Dec 8, 2021 at 09:38 PM, <jakob@...> wrote:
I got a 3D printed cootie from a friend and wanted to test it on my QCX Mini after I had used it a bit on my main rig. By mistake I did plug it into the PTT plug, not as I should have done into the Paddle plug. I powered on and moved the paddle and Bang!! I smelled amperes after I heard a suspicious click in the box. The display went bars. What happened? First and foremost, my mistake to choose the wrong plug for the jack of the cootie. Second, on the cootie stereo jack the tip and the ring are connected together. The result is a perfect shortcut of the +5V bus the ground via the cootie contact.
I have not yet assessed the full damage to the board. It is a Gen 1 version so I guess the voltage regulator is now a solid shortcut.
AA0JR Jakob

 
--
73, Dan - W2DLC


Re: QCX Mini 40M smoked #qcxmini #rip

Steve Greffe - VE3SGV
 

Yup, shorting out the PTT line claimed my 80M Mini too.
But for me it was hot plugging the PTT to the companion 50W amp. Toasted the Ver. 1 regulator and pretty much everything else on the board that was black and had more than two leads. I'm not equipped to do SMD so it was most economical to start over with a new kit, minus the case. Live and learn as they say. Sorry to hear of the magic smoke experiment you had, but don't feel bad--it's easily done and we're not the first.

73
Steve VE3SGV 


Re: 50W Amp problem

K4ALE
 

Evan,
This is hugely constructive and I sincerely appreciate your time and attention to put this together with me. 
Refreshed this morning, I will tackle this again this evening after work as outlined above.
You should be pleased to know that I took each of your prior posts, copied the operative parts, and made a checklist to proceed.
As to the IRF510s:  if a component is available from Digikey or Mouser, that is where I get them.  I have the Vishay parts in my cart at Digi Key in this instance.

The more I mess with this, the more I appreciate the details Hans has taken to design these products, and respect the knowledge required to service, or at least understand the interplay of the components. It's really magic, you know...
Bevin
K4ALE


Re: QCX+ 6 meters ? #6m #qcx

sylcou12@...
 

Thanks Dean,

so a transverter might be the solution then... 
i am not sure though of what frequency would be converted to 6m.  Would it work from 40m?

73,

Sly VA2YZX


Re: #17m #vfo #troubleshoot #qcxmini #17m #vfo #troubleshoot #qcxmini

Hans Summers
 

Hi Paul

If I had your callsign or surname or order ID I could check what you ordered. 

But to me this looks like an issue of having the wrong reference frequency setting (menu 8.5) for your reference option. If you used the 25MHz TCXO you need 8.5 set to 25,000,000 but if you are using the 27MHz crystal, set it to 27,004,000 to start off with. 

73 Hans G0UPL
http://qrp-labs.com

On Thu, Dec 9, 2021 at 2:07 PM Paul <nemo0@...> wrote:
New 17m QCX-mini 1.34 MHz off

Hello, all.  I'm new at this Groups thing, so please do forgive me if my format is incorrect or the question has been asked before.  I've been reading the threads, on and off for about a year, deciding to purchase a pre-built unit for 17m.  Even so, I've not encounter this particular problem in my cursory reading here.

I powered up the mini several weeks ago and was very surprised to hear no signals at all in the amateur portion of 17m.  Even when CW signals are sparse, one can almost always count on hearing FT8 signals, and usually very strong, at their watering hole frequency circa 18100 kHz.  Nothing.

I was, however, able to hear coast station XSQ, transmitting from the Hong Kong area, I believe, and quite well.  But this was outside the ham bands at 18202 kHz.  Well, at least 18202 kHz on my particular unit.

After some very basic tests, I determined that the unit is 1.34 MHz too high.  All the settings look to be correct, from Hans and Co. 

What is happening here?  How do I go about fixing this?

Thank you, kindly.

Paul


#17m #vfo #troubleshoot #qcxmini #17m #vfo #troubleshoot #qcxmini

Paul Cooper, V7/KA4WPX
 

New 17m QCX-mini 1.34 MHz off

Hello, all.  I'm new at this Groups thing, so please do forgive me if my format is incorrect or the question has been asked before.  I've been reading the threads, on and off for about a year, deciding to purchase a pre-built unit for 17m.  Even so, I've not encounter this particular problem in my cursory reading here.

I powered up the mini several weeks ago and was very surprised to hear no signals at all in the amateur portion of 17m.  Even when CW signals are sparse, one can almost always count on hearing FT8 signals, and usually very strong, at their watering hole frequency circa 18100 kHz.  Nothing.

I was, however, able to hear coast station XSQ, transmitting from the Hong Kong area, I believe, and quite well.  But this was outside the ham bands at 18202 kHz.  Well, at least 18202 kHz on my particular unit.

After some very basic tests, I determined that the unit is 1.34 MHz too high.  All the settings look to be correct, from Hans and Co. 

What is happening here?  How do I go about fixing this?

Thank you, kindly.

Paul


Re: #qlg1 #qlg1

Andrew Lenton
 

Hi All,

All good points, and yes there seems to be oscillation, at 5V which a cap did not cure, Data is valid and working at 4.8V at 48mA. Hans came back to me with the answer. see below:

"Hi Andrew

 

 

The T in 74ACT08 means that it has TTL compatible voltage levels. This means a "1" is anything over 2.4V. 

 

The part you used is 74HC08, and has CMOS family voltage thresholds which are higher and are a percentage of the supply voltage. At 5V the 2.8V logic level from the GPS module is not enough to trigger a "1" bit. As you lower the voltage the "1" threshold lowers and this is why it starts to work. 

 

So the cause of your problem is that you chose an unsuitable substitution. You should use either 74ACT08 or 74HCT08 which will also work. 

 

73 Hans G0UPL

http://qrp-labs.com"


It was my TTL to RS232 converter's 12 Volt wire got too close to the 5V line, that caused the destruction in testing, so I just may remove IC1, and put in two transistors to invert the output and run at 12V, the pseudo RS232 (upside down TTL, should work fine on my IC9700, unless it wants a real -12V for logic one? The LEDs' will blink off instead of on, but who cares, as long as the blink.

Why CMOS was not made compatible with TTL is beyond me, the same way the arrow in the transistor points the wrong way, when explaining how a NPN, PNP transistor works is tricky to students, as the current flows from negative earth to the so called positive supply! (why did we do that?)

I was brought up with PNP transistors and positive earth, as in my Philips EE8 kit

73


Andrew G8UUG


Re: Surprised by Tx power

YU1WC Vladimir Ljubojevic
 

George, could you upload the spreadsheet you use to compensate the SWR reading?

I will probably get me one of those QRPGuys SWR/Power meters, so the compensation chart would be handy.

73 Fric YU1WC


Re: QDX #40m #qdx #manual RFSweep waveform different to manual #qdx #manual #40m

Alan G4ZFQ
 

QDX is built and firmware loaded, on dummyload the RF Filter sweep (top) looks quite different than the example in the manual (v 1.06 page 89)  -
Mark,

Assuming v 1.02 is loaded then maybe something in the BPF or LPF.

Do you have TX power on all bands? If not any band maybe LPF switching or bad joint in common path.

The RF sweep checks LPF and BPF so if TX is good then maybe a bad joint on L12.

73 Alan G4ZFQ


Re: QDX 40m Receive/transmit Issue

Alan G4ZFQ
 

On 09/12/2021 01:48, Zachary Painter wrote:
I have noticed my QDX receive on 40m is around half the receive db I am getting on the other bands.  I am also struggling to make any contacts on 40m only.
If your power output is about correct then maybe a bad joint on L12 or one of the 4 associated capacitors.

73 Alan G4ZFQ

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