Date   

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


Re: #qlg1 #qlg1

 

By unstable do you mean oscillation at one or more of the outputs?
Maybe a decoupling capacitor of 0.01u across the power pins right at the chip might help...
--
Julian, N4JO.


Re: 50W Amp problem

Hans Summers
 

Hi TIm, all
 
you made a comment about getting more  IRF510s - be aware that the only mafr of  this IRFs approved by Hans is Vishay.  He tried various other mafr's output and he was not as happy with the results.  All mfr's dies for the semiconductors vary a bit and they are not intended for or tested as RF power amps so it is hardly surprising that some are better than others.

To be clear - what I said was, buy from a reputable distributor. This was the outcome of my own investigations. In the case of IRF510s from Digikey, the only available brand is Vishay (which also happens to be what I am using in the QRP Labs kits). During testing I did also work with original IR-branded parts from Farnell UK and those were fine also. 

What IS a problem, is when you buy "IRF510" from eBay, Amazon, AliExpress, etc. In many (most, even) cases, what you will get is some kind of generic TO220-cased MOSFET which works sort of. I believe these are super-mass-produced and then the manufacturer just slaps various labels on the part, for sales purposes: IRF510, IRF520, IRF530 etc. For many applications you would never know the difference. But in an RF amp the capacitances are of importance. This "generic part", in my testing, behaved more like an IRF530 than a '510. 

So to summarize: my recommendation is, get your IRF510 from a reputable distributor (Digikey, Mouser, Arrow, RS, Farnell, WhatHaveYou), not from online marketplace sales. 

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


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

Dean Smith
 

I've successfully built a 10m version,  but stopped short of 6m one as the fst3253 ic is being pushed a little to far for this band. Having said that I know of one ham that has built and is using one for qrss grabber purposes.
Dean (G7EOB)


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

Mark ZS6MDX
 

Hi

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)  - any ideas? 

Appreciate any help 

73's

Mark ZS6MDX


Re: 50W Amp problem

Timothy Fidler
 

Bevin

you made a comment about getting more  IRF510s - be aware that the only mafr of  this IRFs approved by Hans is Vishay.  He tried various other mafr's output and he was not as happy with the results.  All mfr's dies for the semiconductors vary a bit and they are not intended for or tested as RF power amps so it is hardly surprising that some are better than others.

Don't plug or unplug the  keying cable  from the Qcx Mini to the PA with power on both unless you have a  470 R resistor in the hot lead of that cable and even then it is not a good idea.  The respective  O point of the microprocessor  gets destroyed sometimes when you do this and nobody has  a better fix. The additional resistor in now way affects the control signal but stops  voltage / current being pumped into the  micro'  OP port.   I believe the issue may relate to independent grounding of the   PA and the  Qcx's supply but that's not proven (clearly the zero volts  can be explicitly tied to prevent this if one wishes). 



Re: 50W Amp problem

Evan Hand
 

On Wed, Dec 8, 2021, at 08:38 PM, K4ALE wrote:
I have tested until I am cross-eyed.  From the schematic, pin 1 of the 78L05Z connects to one end of the 4.7 trim pot.  The other end is at ground.  The middle pin (the wiper pin) goes from dead short to ground at full anticlockwise to 2.02 k ohms at highest and back to short at full.  I think the pot is squirrelly and shot.  I also think the two IRF510s are also probably shot, because the gates are not working at all and pin 3 (source) shorts to ground, and I don't see that path on the schematic, except through C6 and C7 (which do not test as shorted.).
So, I will get my hands on a collection of 78L05Zs, IRF510s, proper winding wire, and 4.7k trim pots and rebuild the whole network from regulator through the power transistors.  Unless you have a better suggestion.
Brevin,
The data you just provided indicates that the IRF510 gates are not shorted, as they connect to the R5 wiper and that resistance to ground is changing with adjustment of R5.  If the IRF510s were shorted, pin 2 of R5 would stay at zero ohms.  What could be happening is that IC1 output is shorted.  That would put ground on both sides of R5 and give the results that you are seeing.  In a prior posting, you did state the output of IC1 was 4.97volts.  This does conflict with the current data.

You could do a quick resistance check on the IRF510 drains (middle pin) to ground.  Those should be an open high resistance.  if it is not, then yes, you will need to replace the IRF510s. 

I opened my 50w PA and checked the resistances around R5
Pin 3 is 0 ohms
Pin 2 is 2.41k ohms
pin 1 is 2.94k ohms

That is what I would expect as there is some resistance in the output of IC1 even without power (I stated it should be an open circuit, which is in error).  I did not change R5 as I did not want to upset the bias setting.

Three possible paths forward, all of which will require the removal of the board from the case.
1 - Assume that IC1 is bad.
     a - remove IC1 from the board and verify that now R5 pin 1 measures 4.7k ohms to ground
     b - if R5 measures correctly then replace IC5 and test bias circuit with power applied, the QCX in practice mode, and the PTT line turned on. 
             This should be able to be done with the board out of the case as long as you keep the tabs of the IRF510s from shorting to any ground connections.
             Always use a dummy load when testing, even if you do not expect RF on the output.

2 - Assume that the IRF510s are bad.
     a - Remove both IRF510s (these are best replaced as a pair from the same lot.  That is not required, just reduces bias differences between devices).
     b - Test the bias voltage on both gate pin tabs before putting the IRF510s back in.  You will need the QCX to turn on the PTT line.  Again, make sure the QCX is in practice mode.

3 - Assume there is a wiring or solder problem.
     a - Do the continuity test suggested in the assembly manual
     b - Reheat the coil connections
     c - redo the resistance tests.

When you reinstall the board into the case remember to do the short circuit tests in the manual to verify that the heat sink insulators are keeping the drain tabs isolated from the heatsinks.  This is in section 5 page 40 of the manual.

The above are just suggestions.  Please take proper care when doing the tests with applied power.
73
Evan
AC9TU


Re: 30 M band pass filter #problem #30m #building

Ronald Taylor
 

It’s just an extra. Toss it in your junk box. I suppose you could parallel it with C2 or C5 if one of the trimmers didn’t peak correctly. But you normally just add or remove turns or squeeze or spread turns on the inductors to fix that issue. 

Ron

On Wed, Dec 8, 2021 at 18:56 Syd via groups.io <nhuq1=yahoo.com@groups.io> wrote:
In this kit I have 2 trimmers and 4 caps. C2, C3 & C5 are installed, but the table mentions an "extra" 10 pf and no C4 listed.  I can find nothing about this extra cap and what to do with it. I certainly cannot find anything about it in the manual. What is going on with this cap?
73 wt1v


Re: QDX 40m Receive/transmit Issue

Ronald Taylor
 

Hi Zachary. One possible culprit is the 40 meter lowpass filter since you say receive level is low and transmit power may be low too. Check your soldering and enamel removal on L3 and L8. Also make sure there is continuity between the drain of Q4 and the point where L3 and L8 connect together. If you accidentally lifted the pad when removing the L7 SMD part then the new leader part may not be in the circuit. 

Good luck …. Ron

On Wed, Dec 8, 2021 at 18:48 Zachary Painter <zachary.painter@...> wrote:
Hey I'm sure its something I jacked up but 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.  I'm just curious if there are any components I should look at specifically that wouldn't prevent receive but would make it significantly weaker than other bands?

Thanks again!
 K9WBZ


Re: 50W Amp problem

K4ALE
 

Evan, et als.,
I have tested until I am cross-eyed.  From the schematic, pin 1 of the 78L05Z connects to one end of the 4.7 trim pot.  The other end is at ground.  The middle pin (the wiper pin) goes from dead short to ground at full anticlockwise to 2.02 k ohms at highest and back to short at full.  I think the pot is squirrelly and shot.  I also think the two IRF510s are also probably shot, because the gates are not working at all and pin 3 (source) shorts to ground, and I don't see that path on the schematic, except through C6 and C7 (which do not test as shorted.).
So, I will get my hands on a collection of 78L05Zs, IRF510s, proper winding wire, and 4.7k trim pots and rebuild the whole network from regulator through the power transistors.  Unless you have a better suggestion.

Thank you for your patience and great help.  I have learned a lot tracing all this down.
Bevin
K4ALE


QCX Mini 40M smoked #qcxmini #rip

jakob@...
 

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

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