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Re: #qmx Don’t Use USB-C PD to power your QMX?!
#qmx
My first impression was "What a neat hack!" ?but there are a few unanswered issues besides the ones Hans brings up:
Did you change D108 to a 5V zener? ?Which one? What's the reverse leakage current on that zener? What's the pulldown resistance? What's the transistor? What's the turnon voltage that'll shut down the SMPS pin? More generally, given all the above, what's the Vcc voltage that'll disable the PWM_5V signal? What's the CPU pin configured as, and what are the results of shorting it to ground? [Only Hans knows...] If you put a resistance into the PWM_5V line to reduce the current, how does that effect the drive signal?
73, Willie N1JBJ
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On Sep 3, 2023, at 7:05 AM, Hans Summers <hans.summers@...> wrote:
Hi Gunnar, all
A few comments/questions...
1) this circuit has been proposed, but has anyone actually tried it for real, and then verified that on the step change from 6V to 12V it does protect the circuit without killing the zener?
2) As far as I can see the transistor will be shorting the processor's GPIO pin directly to ground. In other words the transistor will be fighting whatever transistor is inside the microcontroller. Does this worry anyone??
3) More fundamentally... Does it work at all, even theoretically? So the voltage input suddently jumps from 6V to 12V. The SMPS is then running at a too high duty cycle and the voltage at the SMPS therefore jumps. Ordinarily the 5.6V zener is supposed to eat this spike by passing the current to ground. It has to do that for up to 2ms until the processor control loop detects the situation and acts to fix it. Apparently that couple of milliseconds is a bit too much for a 0.5W zeners and there is a possibility of killing it. Which brings me to my question. Now that same current is going through the zener and though the base-emitter junction of the transistor. It could be for a much shorter time because it will (hopefully) win the fight with the GPIO pin and shut down the PWM; still, by that time substantial energy has been stored in the 330uH inductor and now that has to dissipate as a current pulse onto the base-emitter junction of the transistor. Why is the transistor going to survive this?
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Re: #qmx Don’t Use USB-C PD to power your QMX?!
#qmx
Hans, The proposed circuit has problems but the concept shows promise.? I didn't look at it very carefully. I saw the issue of "?the transistor will be shorting the processor's GPIO pin directly to ground. In other words the transistor will be fighting whatever transistor is inside the microcontroller." That could be fixed by adding a resistor in series with the GPIO output pin to limit the GPIO pin's current when the transistor turns on.? I haven't looked at the other more difficult questions you bring up or whether this fixes the input voltage jump issue at all or is it not a robust fix.? I do though like the idea of a "dead-man switch" so no matter what the software is doing, the circuit should have some hardware protection if it can be implemented at very low hardware cost with relatively few components.? OMG the density, the density of that wonderful 3D art packaging.? One can't appreciate it until you get the plugging all the boards together in the final assembly steps!
-Steve K1RF
------ Original Message ------
Date 9/3/2023 7:05:52 AM
Subject Re: [QRPLabs] #qmx Don’t Use USB-C PD to power your QMX?!
Hi Gunnar, all
A few comments/questions...
1) this circuit has been proposed, but has anyone actually tried it for real, and then verified that on the step change from 6V to 12V it does protect the circuit without killing the zener?
2) As far as I can see the transistor will be shorting the processor's GPIO pin directly to ground. In other words the transistor will be fighting whatever transistor is inside the microcontroller. Does this worry anyone??
3) More fundamentally... Does it work at all, even theoretically? So the voltage input suddently jumps from 6V to 12V. The SMPS is then running at a too high duty cycle and the voltage at the SMPS therefore jumps. Ordinarily the 5.6V zener is supposed to eat this spike by passing the current to ground. It has to do that for up to 2ms until the processor control loop detects the situation and acts to fix it. Apparently that couple of milliseconds is a bit too much for a 0.5W zeners and there is a possibility of killing it. Which brings me to my question. Now that same current is going through the zener and though the base-emitter junction of the transistor. It could be for a much shorter time because it will (hopefully) win the fight with the GPIO pin and shut down the PWM; still, by that time substantial energy has been stored in the 330uH inductor and now that has to dissipate as a current pulse onto the base-emitter junction of the transistor. Why is the transistor going to survive this?
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These can also be found for around the same price on eBay sold by rapidonline. Free postage too.?
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Re: #qmx Don’t Use USB-C PD to power your QMX?!
#qmx
Hi Gunnar, all
A few comments/questions...
1) this circuit has been proposed, but has anyone actually tried it for real, and then verified that on the step change from 6V to 12V it does protect the circuit without killing the zener?
2) As far as I can see the transistor will be shorting the processor's GPIO pin directly to ground. In other words the transistor will be fighting whatever transistor is inside the microcontroller. Does this worry anyone??
3) More fundamentally... Does it work at all, even theoretically? So the voltage input suddently jumps from 6V to 12V. The SMPS is then running at a too high duty cycle and the voltage at the SMPS therefore jumps. Ordinarily the 5.6V zener is supposed to eat this spike by passing the current to ground. It has to do that for up to 2ms until the processor control loop detects the situation and acts to fix it. Apparently that couple of milliseconds is a bit too much for a 0.5W zeners and there is a possibility of killing it. Which brings me to my question. Now that same current is going through the zener and though the base-emitter junction of the transistor. It could be for a much shorter time because it will (hopefully) win the fight with the GPIO pin and shut down the PWM; still, by that time substantial energy has been stored in the 330uH inductor and now that has to dissipate as a current pulse onto the base-emitter junction of the transistor. Why is the transistor going to survive this?
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Re: QMX Shipped, panic stage
#qmx
Billy, et al,
If you are going to continue building kits like this you definitely need this:
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There are cheaper versions elsewhere. I kept my two units when I retired from medical practice and use them daily for radio and other household repairs (and sliver removal too). ?The Donegan products are cheap when you figure how much you will use them. ?Radios and radio parts aren’t getting any larger these days. ?If you look around there was a useable unit a few years ago for less than $15. I bought one for my grandson and an extra one for me. ?Works better than Hans suggested jewelers loupe. Two eyes are better than two. ?
Also using your smartphone camera and enlarging the photo to look at certain areas in greater detail is also a use for an older smartphone….. I have the iPhone 12plus (larger screen) and the camera part is worth the cost of the phone to me at times looking for whiskers and other shorts….. did I say reading the little numbers on the small parts? ?I couldn’t build without it. ?
Dave K8WPE since 1960
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On Sep 1, 2023, at 7:35 AM, N5SE <bwmoore@...> wrote:
?
Karl, you sent this to the WRONG topic and guy. NOT ME! Checking all messages sent on groups.io, I found the original message as below. Not upset, trying to help both of you.
["Dire need of a part
David R Hassall WA5DJJ
Dear group,
While convalescing with all the ills I have acquired since July 4th, I decided to dig into my kit pile and spend the time building the neat kits that I had bought. ? While working on a QDX Rev
3, I was building along and noticed that L11 looked funny. ? It was broken in half. ? I may have done it or some shipper may have. ?I am not concerned with "who killed John". ? I just need a part. L11 is a SMD 47uh choke. ? I thought I had a "hanger queen"
QDX but I think someone else got it when they need a part.
So I need an SMD 47uh choke for my QDX. ? Does anyone have a stock of them that would part with one or two? ? I will pay postage etc. as required.
and if you bought them I will pay for two. ?I just need the part and don't think that DigiKey ?would be happy for a order and the postage would not be pretty.
Thanks for the time and I hope I can come up with one of these so I can get my QDX running. ? Address is good in QRZ .
73 Dave WA5DJJ
SUPER GRABBER https://www.qsl.net/wa5djj/
?WEBSITE: ? "]
Send Dave WA5DJJ this information, I am sure he will appreciate it.
Have you checked this yet?
<Screenshot_20230901-060851_DuckDuckGo.jpg>
--
73
Karl
KI4ZUQ
--
N5SE
Billy Wayne Moore
7066 Shady Knoll Ln
Willis, TX 77318-6324
Phone: 936-537-2975???
Re: #QMX #BPF problems with fault finding
#qmx
#bpf
Chris and Mike
Thank you for your input, it is much appreciated. Today propagation is s**t so good time for tinkering with radio gear. I will report later on today.
---------------------------------
73 de Marek SP9TKW
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possibly either a duff jack socket or duff phones..
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On 2 Sep 2023 at 7:34, Donald Gover wrote:
Well I have tried all the suggestions, quadruple checked the solder joints.
There is NO sound other then the initial click at power up. It will work fine
on Ft8. With FLdigi I can decode CW. The Device successfully Will transmit CW
and decode CW both with the Key and on the air. Just nothing out of the head
phone jack. I purchased another kit and am going to build it and then compare
and contrast the two. If anyone has any other suggestions I'd love to try
them.
Don..
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Interestingly, they are cheaper in the USA but its a UK based Welsh company..
Rip-off Britain again !
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On 2 Sep 2023 at 10:05, Mike Besemer - WM4B wrote: Or for those of us in the U.S.:?? t4857/?brutto=1¤cy=USD&gclid=Cj0KCQjwusunBhCYARIsAFBsUP_EVi8PHCBtLhehgC7g 3LPECuCShiVZ8q6sFk2P3BPtWFl2e3lDm8AaAlD9EALw_wcB 开云体育 Links: You receive all messages sent to this group. View/Reply Online (#109102) | Reply To Group | Reply To Sender | Mute This Topic | New Topic Visit group: /g/QRPLabsQRP Labs webpage: QRP Labs shop: Your Subscription | Contact Group Owner | Unsubscribe [mike@...] -- Linux is free if your time is worthless
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Re: QDX - protection of BS17O PA
Here’s how I’ve protected the BS170’s with Zener diodes with no side effects as far as I could tell. It’s been reported here before, but I hope it’s OK repeating? -- Sverre
LA3ZA
http://la3za.blogspot.com
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shop.qrp-labs.com Forgot Password
Morning Hans,
I am trying to reset my QRPLABS password.
However, I dont get the email...
?An email with a confirmation link has been sent your email address.
Is there a known problem currently with resetting one's password?
73 Stewart
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Re: #qmx Don’t Use USB-C PD to power your QMX?!
#qmx
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Re: #qmx Don’t Use USB-C PD to power your QMX?!
#qmx
There is such a solution, please refer to /g/QRPLabs/message/108946
With this mod, the QMX will be immune to input voltage steps, and I believe it will not confuse the software regulator.?
I have sent for the parts and will modify my QMX next week.?
This is such a smart fix and should be a candidate for the rev 2 board!?
73 de SM5EIE /Gunnar?
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Re: QDX - protection of BS17O PA
Dear Paul,
Thank you for that clarification.?? 1N4148 across the choke? with the cathode towards the 12V lead.?? OK? I got it.
Take care and have fun.? Happy Labor Day weekend
73 Dave WA5DJJ
SUPER QRSS/WSPR GRABBER
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Re: #qmx Don’t Use USB-C PD to power your QMX?!
#qmx
Brainstorming. Don't have the schematic in front of me... How
about if something were added to rob the SMPS of drive, when that
rising voltage transient occurs?
On 9/2/23 16:59, Roy - KI0ER via
groups.io wrote:
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So after a month using my QMX with great success. However, it's
now broken ;-( ... likely due to this current discussion. It was
powered up, not transmitting, and the power cord going to a 12V
trigger USB-C device got bumped when I turned my PC a bit. So I
suspect it took a 5v to 12v power hit.
I've not opened it up yet, but the QMX powers up, menu works,
hardware diagnostics on the terminal all look good including
showing power from the 3.5v and 5V supplies in the hardware
diagnostics as expected. But I just get static noise on the
audio output, and all the RF filters sweeps which used to look
great, are all garbage. Paddle input does not work in Practice
Mode like it used to.
Would these symptoms point to that D108 Zener, or do I have
something else gone wrong?
I'll be digging into it later this week to see what I can see.
Thanks!
Loved this little QMX while it worked, so am anxious to get her
back on the air!
73
de Roy - KI0ER
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Re: QDX - protection of BS17O PA
"There was mention of putting a 1N4148 across the choke but was
confusing as to which way to mount it"
David-- Cathode towards Vcc!
Paul -- AI7JR
On 9/2/23 16:11, David R. Hassall
WA5DJJ wrote:
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Dear Group,
I am just finishing up 5 QDX's ..... 3 Rev 3's and 2 Rev 5's.???
I have been trying to follow this thread but it is a little
confusing as to what modifications really help prevent
destruction of the PA transistors and what parts to use
one should use.... There was mention of putting a 1N4148 across
the choke but was confusing as to which way to mount it and
something about using a power supply at 12V @1 amp.?? There
there was two or three messages that put two diodes (zenners or
TVS???)and one had them hooked to a different spot than the
others.?? Since, I am a careful sort, who follows Hans Summers
instructions to the limit.? But I have also had BS170 FETs fail,
I would like to give my 5 QDX's at least a fighting chance of
survival,? I would really like to see a message from some one
that explains what to do and what to use with part numbers to I
can keep all my new QDX's running for a long time.? At least as
good as my original version 1 which is still going strong after
a couple of final transistor failures and an IC5 failure.??
Hope everyone has a great week.?? If anyone needs any 0805 47uH
inductors like L11, I will have 200 of them after September 15
and will gladly share.?
Take care and have fun.
Dave WA5DJJ
SUPER QRSS/WSPR GRABBER
?
?
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Re: #qmx Don’t Use USB-C PD to power your QMX?!
#qmx
Forgot to mention that I am getting about 5W out when I transmit ("T" key) from the hardware test Diagnostics screen. And I also did a Factory Reset (for the first time), and that has not helped; still get nothing but static on audio.
Ideas on what I may have fried?
Roy - KI0ER
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Re: Blew the PWR_HOLD port on the CPU
#qmx
Perfect! And you didn’t even have to mod your board to “fix”.
-Mike/w1mt
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Re: Blew the PWR_HOLD port on the CPU
#qmx
Hi Mike,
I share your pain.? Mine seems to be blown too, but instead of grounded, mine is sitting at 2.48V.? This is not so bad as when you press the left encoder, it powers up and stays up.? It won't shut down though.? When the left encoder is pressed again, it shows shutdown but stays on.??
The port was damaged when moving Q103.? A tiny almost invisible solder whisker between Q103 source and the connector JP102 pin 7 sent Vcc to the power hold port.? There isn't much clearance between those pads.
Glenn VK3YY.
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Re: #qmx Don’t Use USB-C PD to power your QMX?!
#qmx
So after a month using my QMX with great success. However, it's now broken ;-( ... likely due to this current discussion. It was powered up, not transmitting, and the power cord going to a 12V trigger USB-C device got bumped when I turned my PC a bit. So I suspect it took a 5v to 12v power hit.
I've not opened it up yet, but the QMX powers up, menu works, hardware diagnostics on the terminal all look good including showing power from the 3.5v and 5V supplies in the hardware diagnostics as expected. But I just get static noise on the audio output, and all the RF filters sweeps which used to look great, are all garbage. Paddle input does not work in Practice Mode like it used to.
Would these symptoms point to that D108 Zener, or do I have something else gone wrong?
I'll be digging into it later this week to see what I can see.
Thanks!
Loved this little QMX while it worked, so am anxious to get her back on the air!
73
de Roy - KI0ER
|
Re: QDX - protection of BS17O PA
Dear Group,
I am just finishing up 5 QDX's ..... 3 Rev 3's and 2 Rev 5's.??? I have been trying to follow this thread but it is a little confusing as to what modifications really help prevent destruction of the PA transistors and what parts to use
one should use.... There was mention of putting a 1N4148 across the choke but was confusing as to which way to mount it and something about using a power supply at 12V @1 amp.?? There there was two or three messages that put two diodes (zenners or TVS???)and one had them hooked to a different spot than the others.?? Since, I am a careful sort, who follows Hans Summers instructions to the limit.? But I have also had BS170 FETs fail, I would like to give my 5 QDX's at least a fighting chance of survival,? I would really like to see a message from some one that explains what to do and what to use with part numbers to I can keep all my new QDX's running for a long time.? At least as good as my original version 1 which is still going strong after a couple of final transistor failures and an IC5 failure.??
Hope everyone has a great week.?? If anyone needs any 0805 47uH inductors like L11, I will have 200 of them after September 15 and will gladly share.?
Take care and have fun.
Dave WA5DJJ
SUPER QRSS/WSPR GRABBER
?
?
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David Wilcox K8WPE
Marek SP9TKW
Mike
Stewart ZR1WT
Paul - AI7JR
Glenn S