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QMX+ V2 - I've killed it
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Reassuring that the load is fairly constant.
Interesting or not, I would not vary the Vdd load if the 3.3v SMPS
is still hooked up to the rest of the board.
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A case of me creating a problem that doesn't need solving.
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Jerry, KE7ER
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On Mon, Oct 28, 2024 at 10:01 PM, Hans Summers wrote:
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Soundcards would have AC coupled audio inputs.
So won't work to monitor DC levels, even with appropriate scaling resistors.
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Jerry, KE7ER
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On Mon, Oct 28, 2024 at 06:17 PM, Jerry Gaffke wrote:
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开云体育Jerry, 1) I am not sure I will be able to assemble it, not willing to
touch a functional unit afterwards. I won't touch anything on the
QMX+ board, except to probe some analog voltage eventually and
injecting digital commands (like mimic encoders and pushbuttons).
Too risky already, I will surely make the magic smoke come out
fiddling. Could just testing the power without touching anything
else as first test, then add paddle and encoders control. 3) If SMPS alone and in itself is the TOE, well we will stick to the SMPS but since V2 has them onboard, for the QMX+ alone that make less sense to me. 4) This is somewhat? different on QMX, I preferred the QMX+
because size does not bother me and I hope it will be easier to
assemble. I have successfully completed a QCX on 20m, while a 30m
and 40m are still to be assembled, fearing the mod for the LDO. I
also have a QCX+ that I like very much.
Alan, >Record via COM or USB I can use a Teensy, it has some ADC inputs, 10bit resolution, and if needed is fast. Else I can use my multimeter, but I would need to create a program for it and it will be much slower (like some readings/s max). Probably the best option is to have a DSO trigger on some kind of overshoot and capture programmatically(if I know what to look for of course, trigger options can't do AI yet), Let's assemble the QMX+ I will start slow with a Teensy, a relay for the power and something to measure Power supply and current. Any suggestion for a schematic for controlling a Mosfet instead of the relay, in any case with a opto-coupler? Which Current range should I monitor? TIA |
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The Teensy could do it.
Ideally, it samples the 12 bit ADC's at around one millisecond, and sends that on
to a USB host computer as they happen.? The host computer can store hours
of readings to disk.
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Two ADC channels might be sufficient, just Vin and VDD.
If you have two more channels, then could also monitor PWM_3V3 and ADC_3V3.
ADC_V3V since there will be a voltage drop across Q111 due to on resistance.
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Don't; need to monitor current, Hans has said current should be fairly constant,?
and that can be verified by watching the difference between ADC_3V3 and VDD.
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Q101, Q102 and R102 show how to switch a 12v supply using a 3.3v logic signal
from the Teensy.? R101 is not needed, since the Teensy output will never be?
tristated.? Power the rig from a 7 volt supply through a diode, the diode prevents
the 12v supply from pushing current back up into the 7v supply when the switch
is on.
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Much easier would be to just monitor VDD with a scope while wiggling the power?
connector.? That may be good enough.? But going further could be fun.
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Jerry, KE7ER
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You could have a 6 or 7 volt supply giving the rig power at the normal power port
through a diode to prevent flow of current when rig voltage rises due to the 12v switch.
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On Tue, Oct 29, 2024 at 03:53 AM, Giuseppe Marullo[iw2jww] wrote:
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Robert AD6XJ
Great suggestion Don. I'm wondering if a TL431 could do D109's job. Also wondering if some robustness would be obtained by paralleling a pair of 3.6V 500mW zeners in D109's place without sacrificing any of the desired properties of a single component.
Someone previously said "most of these (zeners) fail shorted" implying that some fail open...could that be the case in Han's example that he shared was demonstrably reliable? The radio continues to work without D109 so without it crowbarring the 3.3 rail one would not notice that it failed open (like a fuse) until the next microcontroller blasting spike occurs.
'73 Robert AD6XJ |
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It’s hard to say whether paralleling two 3.6V, 1/2W Zeners in place of D109 would be more robust. Doing so *might* keep the 3.3V rail at or below the 4V maximum rating of the MCU’s 3.3V power rail in a given failure scenario. The problem is we don’t know how much current it takes to melt these Zeners into a short, how long it takes for them to fail, nor how much current can flow through Q111 during a failure condition. You might run a test outside of the radio with a couple of them in parallel and slowly crank up the current while measuring the voltage across them. Looking at the I/V curves Hans supplied, I doubt you’ll gain much, if anything, additional protection. Tony On Tue, Oct 29, 2024 at 4:13?PM Robert AD6XJ via <91710robert=[email protected]> wrote:
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Robert AD6XJ
Thanks Tony,
I am one of the two jiggling the power cord failures Hans found in his D109 search. I think his 50 of thousands data is corrupt because I've seen posts where the QMX+ died but the builder didn't know why (so no "D109" data as yet) so several QMX+ deaths might not post "D109".
My exact conditions of death were-- AF connected to 99? store amplified speaker using a pair of AAA batteries, a key (VK3IL pressure paddle ), a dummy load which I was swapping for telescoping BNC antenna, and most important-- a 12V WARRIOR Harbor Freight Drill battery connected to my QMX+ with alligator clips. As I was changing from the dummy (50Ω) load to the whip I bumped the alligator clip on the negative post, presumably dropping input voltage to zero then back to 12VDC very quickly. Perhaps (said with great caution) the BMS on the HFT drill battery, which normally delivers a nice 12VDC, saw the absence of, then presence of, current and did some Whacktacular voltage swing? Or the L/C in the QMX was...? I'm glad a friend is mailing some zeners to me so I can "safely" use my QMX+ (it works fine with no D109, but dad {Hans} says that's a no-no, and I believe him). If any of you adventurous types don't want to build a computer controlled switching relay assembly test set-up and maybe find it easier to jiggle an old alligator clip to stress test your QMX+ I'm sure dad {I mean Hans} would like to hear the results, as would I. I am quite curious if the battery's BMS might be at fault instead of the SMPSU in the rig.
We will solve this, if only for the fifty few.
73 Robert AD6XJ
PS "crowbar" is what D109 does, not "fuse". |
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The D109 failure of my QMX was apparently caused by a short 12V power fail.
I didn't notice that my DC power plug is a 2.5mm size plug, and did not even know that there are 2.1mm and 2.5mm versions.
Well, it worked OK perhaps 10 - 20 times until I somehow touched the plug and the QMX got quite warm and did not react in any way. The 3.3V SMPS was burning hot.
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I replaced the SMPS'es by the ones borrowed from my QMX+. Everything works, but no output power. The hardware test shows 1.0 SWR and 0.0W output power on all bands. Of course all filter and swr sweeps fail when there is no output.
What to do next? Is it enough to replace the PA transistors?
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I feel that the QMX should have some protection against such short power inerrupts.
This is very important. As the SMPS voltages are controlled only at 1ms intervals, it is clear that the design relies on the assumption that no millisecond-scale power failures can occur.?
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Could it be as simple as adding a suitable large electrolytic capacitor to the pins of the 12V power input jack?
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73 Matti OH6BEX |
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Matti, a couple of comments:
1) Keep in mind that using the wrong power plug with a too-large inner conductor hole, may well have caused dozens of very short power interruptions, perhaps some every time you used it.? So it wasn't necessarily a single power interruption that caused the failure.
2) Hans has described several times why he believes the 1ms scan has very little to do with sub-millisecond power failures, so there may be something else going on here.
3) The 3.3V supply has nothing to do with the PA transisitors, so I wouldn't assume that they are the problem.? The IC501/502 xor gates that drive the clock into the transmitter are powered by the 3.3V supply, so you may want to check those.? Check first to see if there is a transmit-frequency clock on CLK2 out of the 5351, then see if it also appears on the output pins of IC501 and 502.
4) When it is determined what really causes the failure, then we can tell whether adding a large-value electrolytic cap to the input or 12V rail would help - but it probably wouldn't hurt.? Certainly using the correct power connector will help.? That one is easy.
Stan |
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On Wed, Oct 30, 2024 at 03:03 AM, holoma47 wrote:
I'm not at all sure this will help because when there is a power interruption the big capacitor will hold the voltage up for longer so that there is more time for the SMPS controller to react, trying to keep the voltage up. Then when the voltage is restored a lot of current can flow into the SMPS before the controller has had a chance to react.
Robert's description of his failure conditions - using a battery capable of delivering a lot of current may also be significant.? I'd actively avoid any sort of controllable power supply if I was trying to induce this problem.
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BTW I've seen the 2.5mm vs 2.1mm power plug issue a lot but most power supply circuits don't fail and all that happens is that people complain of things shutting down or running incorrectly.? Computer controlled telescopes had this a lot.
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Chris, G5CTH |