Re: QDX and QMX+ (soon at least) what is the max safe swr?
Chris,
As I've stated many times before, NEVER exceed the absolute?maximum rating of a semiconductor as spec'd by the manufacturer. Doing so is asking for trouble, possibly short term, or maybe a gradual weakening of the device under stress until it fails long term. Furthermore, relying on a manufacturer?underrating their device is a bad idea. I've seen a few manufacturers underrate by as much as 20% but this is not at all typical across the semiconductor industry. You'll find that many devices have very little safety margin relative to their maximum ratings so my advice is to never exceed?the manufacturer's specs under any conditions.
As far as current-limiting to 100 uA or so during breakdown testing, I don't think it will save you from?permanent?damage but you can certainly try this on your first DUT and see what happens. If you see some odd behavior after the FET breaks down, you should consider it unreliable even if it seems to work when the voltage is lowered. I always consider breakdown voltage testing as destructive. If you test multiple devices, I'm not sure what the stats will look like unless you're willing to test hundreds of them. The same goes for any TN0110 testing you consider trying.
Your zener fix was one of a few that were discussed way back when. Hans added diode?pads to the schematic so he was OK with this workaround.?
How many BS170's are you planning to perform breakdown testing on?
Tony
On Tue, Sep 17, 2024 at 12:48?PM Chris KB1NLW via <chrisrey1= [email protected]> wrote: Thanks Tony;
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After I get the dissipation concluded I am thinking of measuring breakdown of my batch of BS170.? I think the QMX design is relying on the typical breakdown being significantly higher than the speck.? If I do this I should also check TN0110.
?
I'm thinking of limiting current during breakdown to ~0.1ma (concerned about damage), any thoughts?
It does seem that Hans should be more concerned.
?
?
I have three QMXs that have zeners across the BS170s.? Before I added the Zeners I had multiple failures, none since!
Of course I don't have them in my QMX+ so I could do these test.??
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Re: QDX and QMX+ (soon at least) what is the max safe swr?
Hi Chris
That is pretty bad luck. I have been operating QRP labs radios without any mods almost constantly since 2018 and never had any issues with finals. One was also working WSPR non stop.
It is very odd why only some folks suffer from blowning finals, given the vast number of sets Hans has sold.
I would be curious to learn about your antenna and PSU. Do you use an ATM?
I really hope you find the cause.
73s Ted
2E0THH
??
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Re: QDX and QMX+ (soon at least) what is the max safe swr?
Have you tried another tuner?? I find that mine is pretty much a dud, even after hours wasted troubleshooting it.? Maybe that's the issue.?
-Bill? W3WJ
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Hi Sardar;
Just saw your follow-up message.
1) With 9 - 12 Volts applied to the QMX+ power jack, what voltage do you see at the 3.3 Volt output of IC101 (78M33 3.3 Volt regulator) on plug-in power supply module pcb #2 when you press the power button?
2) With 9 - 12 Volts applied to the QMX+ power jack,?what voltage do you see at any of the VDD pins on the main board when you press the power button?
73, Steve, N3SB?
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-------- Original message -------- From: me@... Date: 9/17/24 10:55 AM (GMT-05:00) Subject: Re: [QRPLabs] QMX+ is dead after voltage drops to 5V #ATmega328 #QMXplus
Some details:
?
Correction: Arduino on dev board was powered from Vcc (5V) on JP106.
?
Firmware was 27.
Can not go to firmware update mode even with the jumper wire (Aux2 to ground).
When plugged to PC - no COM port to try putty. So, board exhibits a brain death.
?
When 12V applied and PWR encoder is long pressed - voltage on JP106 from VCC and GND goes to 0.1V then gradually within few sec drops to 0V.
?
Any help would be appreciated.
?
--
73,
Sardar ( AC8L).
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Re: QDX and QMX+ (soon at least) what is the max safe swr?
Thanks Tony;
?
After I get the dissipation concluded I am thinking of measuring breakdown of my batch of BS170.? I think the QMX design is relying on the typical breakdown being significantly higher than the speck.? If I do this I should also check TN0110.
?
I'm thinking of limiting current during breakdown to ~0.1ma (concerned about damage), any thoughts?
It does seem that Hans should be more concerned.
?
?
I have three QMXs that have zeners across the BS170s.? Before I added the Zeners I had multiple failures, none since!
Of course I don't have them in my QMX+ so I could do these test.??
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Re: QDX and QMX+ (soon at least) what is the max safe swr?
Hi Chris,
Long ago, JZ noted high-voltage peaks exceeding 100V at the BS170 drains. They showed up in simulations we ran as well. There were some fixes suggested which seem to calm things down a bit but based on our results, I recommended TN0110 as an alternative device for two reasons - 100V Vds max and lower Vgs threshold to enable harder saturation with the existing 5V drive level. With the BS170, I had to drive the simulation from about 6.5V at the gate to get the same output as TN0110 with 5V at the gate.
Your first graph highlights the dangers of reflections but I also conclude that the higher frequency bands are ¡°safer¡± which is likely due to less gain at those frequencies.
Tony AC9QY
On Mon, Sep 16, 2024 at 5:30?PM Chris KB1NLW via <chrisrey1= [email protected]> wrote: I'm doing a deep dive into cause of BS-170 failures.??
Currently I have finished evaluating peak BS-170 Drain to Source voltage and am in the middle of power dissipation for various SWRs.
- On 160m and 80m Peak voltage exceeds the BS-170 60v spec.? Probably should not use at 12V operation, particularly at 160m
- Using an Elecraft TI ATU there are spikes during tuning of over 100v!
I will am putting together a detail presentation.? Here are a couple of charts:
?
?
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Hi Sardar;
VDD in the QMX+ is 3.3 Volts. Is this what you had your Nano connected to?
Can you explain what you mean by "showed 5V" - how was this voltage measured?
73; Steve, N3SB?
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------- Original message -------- From: me@... Date: 9/17/24 1:26 AM (GMT-05:00) Subject: [QRPLabs] QMX+ is dead after voltage drops to 5V #ATmega328 #QMXplus
Hi,
?
I was experimenting with a dev board and Arduino Nano on it powered through QMX+ Vdd. Everything was going on fabulously until I turned radio off while ardiono was plugged to PC through USB for programming. Radio turned off, then showed 5V and that was it. It does not come back anymore.
?
Is there a chance I can revive the board or it is gone?
--
73,
Sardar ( AC8L),
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Re: A ¡°pluggable¡± firmware architecture?
On Tue, Sep 17, 2024, at 16:46, Mike KK7ER wrote:
In my teens, I spent quite a few hours with the latest Commodore 64 magazine entering (literal) pages of assembly code one byte at a time (remember PEEK and POKE?? :)).
Checksums prevented most typos.
At the end, the payoff was getting to play some new game described in the magazine.
My first word processor came out of _Compute!_ magazine!
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Re: A ¡°pluggable¡± firmware architecture?
DLL?? Perhaps. I was thinking more like JNI (Java Native Interface) in a Java VM.
https://docs.oracle.com/javase/7/docs/technotes/guides/jni/spec/intro.html
?
In my teens, I spent quite a few hours with the latest Commodore 64 magazine entering (literal) pages of assembly code one byte at a time (remember PEEK and POKE?? :)).
Checksums prevented most typos.
At the end, the payoff was getting to play some new game described in the magazine.
?
If we will be able to enter a BASIC program into the QMX over the serial terminal, it should be possible to store literal machine code along with the BASIC source code.
Just a thought, although I can appreciate how it might be beyond the scope of what you had planned.
?
73, Mike KK7ER
?
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Re: New Build but can¡¯t get firmware to load
Thanks for that info. I actually have ordered some inductors so I¡¯ll wait for the replacement. In the mean time, I had already ordered 2 (accidentally) 15-60 units. I will only need one so I can use the PCB2 from the extra to get this one running so I can find what OTHER surprises await!!!?
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Not being critical, but ...
I remembered seeing a pretty clear warning, highlighted in red, about not drawing any appreciable current from the VDD OR VCC rails when interfacing through the dev board. It's on page 68 of the assembly manual.
Hopefully new SMPS board(s) will bring it back to life.?
Greg
On Tue, Sep 17, 2024 at 10:55 AM, me@... <me@...> wrote: Some details:
?
Correction: Arduino on dev board was powered from Vcc (5V) on JP106.
?
Firmware was 27.
Can not go to firmware update mode even with the jumper wire (Aux2 to ground).
When plugged to PC - no COM port to try putty. So, board exhibits a brain death.
?
When 12V applied and PWR encoder is long pressed - voltage on JP106 from VCC and GND goes to 0.1V then gradually within few sec drops to 0V.
?
Any help would be appreciated.
?
--
73,
Sardar ( AC8L).
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Re: New Build but can¡¯t get firmware to load
And don't worry about trying to connect that lead under the edge of the coil form, which could be very difficult.? Depending on which side of the coil was disconnected (it's hard to tell from your photo), it can be connected to the top terminal of D107 or C106.? See the schematic and board drawings.?
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Re: QMX+ High Current and Self Start
On Tue, Sep 17, 2024 at 03:17 AM, Damon wrote:
V+ takes a couple of minutes to build up
You definitely have a bad or misplaced component in the Vin circuit.? The voltage should come up in milliseconds.?
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You likely back-fed 5V from the USB into the un-powered QMX 5V power supply, killing it.? Looking at the schematic, you may have fried Q108 or Q105.? I would check that area of the circuitry.
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Sardar, did you measure Vdd when pressing the PWR On command. If you did and it was not there either, you might try a new 5 volt power regulator board. It may have been damaged by the backfeed, although I can't see the reason that might?happen. But it does provide for the initial startup sequence of events by seeing the Power On command from the switch and supplying 12v to the linear regulator which then boots up the processor which sends PWM back to both regulator boards and shuts down the linear regulator. Just a thought ... Ron
Some details:
?
Correction: Arduino on dev board was powered from Vcc (5V) on JP106.
?
Firmware was 27.
Can not go to firmware update mode even with the jumper wire (Aux2 to ground).
When plugged to PC - no COM port to try putty. So, board exhibits a brain death.
?
When 12V applied and PWR encoder is long pressed - voltage on JP106 from VCC and GND goes to 0.1V then gradually within few sec drops to 0V.
?
Any help would be appreciated.
?
--
73,
Sardar ( AC8L).
|
Re: QMX+ test ADC I/Q shows one phase missing
I¡¯ve seen this before. ?It¡¯s difficult to diagnose without a scope. ?But if you have a multimeter you can check the dc bias. ?There should be about 2.5 volts dc on pins 1 & 7 of IC405 & IC406. ?Also check the soldering on the trifilar transformer and make sure it¡¯s installed correctly. ?Beyond that, a scope would be helpful.
?
good luck.
--
73
Jeff Moore
W1NC
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Some details:
?
Correction: Arduino on dev board was powered from Vcc (5V) on JP106.
?
Firmware was 27.
Can not go to firmware update mode even with the jumper wire (Aux2 to ground).
When plugged to PC - no COM port to try putty. So, board exhibits a brain death.
?
When 12V applied and PWR encoder is long pressed - voltage on JP106 from VCC and GND goes to 0.1V then gradually within few sec drops to 0V.
?
Any help would be appreciated.
?
--
73,
Sardar ( AC8L).
|
Re: QDX and QMX+ (soon at least) what is the max safe swr?
Donald>
I totally agree phase of the reflected power is critical for each of the harmonics, thus affecting how the two components from the LPF and SWR will add or subtract,? and affect the peak voltage across the BS-170.? I have probably 40 scope photos and a few hundred measurements showing this.? Ultimately I will publish much of this info.
?
In the past I have stated that BS-170 failures are most likely from excessive D-S voltage.? My effort demonstrates this is the case for both some bands and steady SWR and very bad for ATUs during tuning.??
Anyone with a good scope and the ability to make dummy loads of various impedances can replicate this.?
Can you do similar test?
(FYI I have the same digital scope as Hans).
?
Currently I'm in the middle of determining BS170 power dissipation -? a little more difficult? since it require differencing various power dissipations.? So far I have used two approaches and now looking at a third approach to see if I can get more consistent results.
?
(In the past I have been responsible for many failure analyses for NASA and the Military so I may be a little anal for Ham applications)
?
?
?
?
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Re: QMX+ High Current and Self Start
On Tue, Sep 17, 2024 at 12:17 PM, Damon wrote:
V+ takes a couple of minutes to build up from Vin upon first application of input power.
Sorry, what do you mean by "V+"?
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Re: New Build but can¡¯t get firmware to load
Don't worry if you need to unwind a turn or two to make slack.? The circuit will still work fine?
73, Don N2VGU?
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Ted 2E0THH
Ronald Taylor
Donald S Brant Jr