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Yesterday, I ran my QDX for the first time off a 9V / 160 mA power adapter. You know, one of those things similar for charging your phone.
It was receiving properly, and I was even able to make some QSO's.
Today, I decided to use the same kind of power adapter, but this time a 9V / 1A version.
The QDX started out normally by flashing the led rapidly, then the led went off and smoke came from the QDX.
What in Earth may have happened here ?
I did not raise the voltage. The only thing that was new was that the adapter can supply more amps.
Any help would be appreciated.
Tnx,
73 Hans
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Hans, ? Is the +9V/1A supply regulated?? How much voltage do you measure from it? ? Paul, W9AC ?
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From: [email protected] < [email protected]> On Behalf Of PA3CRZ via groups.io Sent: Saturday, July 22, 2023 12:18 PM To: [email protected]Subject: [QRPLabs] Another QDX went up in smoke ? Yesterday, I ran my QDX for the first time off a 9V / 160 mA power adapter. You know, one of those things similar for charging your phone.
It was receiving properly, and I was even able to make some QSO's.
Today, I decided to use the same kind of power adapter, but this time a 9V / 1A version.
The QDX started out normally by flashing the led rapidly, then the led went off and smoke came from the QDX.
What in Earth may have happened here ?
I did not raise the voltage. The only thing that was new was that the adapter can supply more amps.
Any help would be appreciated.
Tnx,
73 Hans
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I MHO, unless you have a genuine regulated power supply, ALL QRP rigs should be run from battery power only and even then the voltage should be very close to the specs of the rig without using buck converters unless a dedicated one.
Possibly your PS initially puts out excessive voltage?
John? KK4ITX? ?Each mistake is a learning opportunity.?
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On Jul 22, 2023, at 12:25 PM, Paul Christensen <w9ac@...> wrote:
? Hans, ? Is the +9V/1A supply regulated?? How much voltage do you measure from it? ? Paul, W9AC ? ? Yesterday, I ran my QDX for the first time off a 9V / 160 mA power adapter. You know, one of those things similar for charging your phone.
It was receiving properly, and I was even able to make some QSO's.
Today, I decided to use the same kind of power adapter, but this time a 9V / 1A version.
The QDX started out normally by flashing the led rapidly, then the led went off and smoke came from the QDX.
What in Earth may have happened here ?
I did not raise the voltage. The only thing that was new was that the adapter can supply more amps.
Any help would be appreciated.
Tnx,
73 Hans
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That’d do it.? I have a good, regulated supply, but when set to 5 VDC (for my U3) the voltage will spike on turn-on.? Took me a while to figure out why I was toasting microprocessors.? ? Mike WM4B ?
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From: [email protected] < [email protected]> On Behalf Of KK4ITX John via groups.io Sent: Saturday, July 22, 2023 5:43 PM To: [email protected]Subject: Re: [QRPLabs] Another QDX went up in smoke ? I MHO, unless you have a genuine regulated power supply, ALL QRP rigs should be run from battery power only and even then the voltage should be very close to the specs of the rig without using buck converters unless a dedicated one. Possibly your PS initially puts out excessive voltage? KK4ITX? ?Each mistake is a learning opportunity.?
On Jul 22, 2023, at 12:25 PM, Paul Christensen <w9ac@...> wrote:
? Hans, ? Is the +9V/1A supply regulated?? How much voltage do you measure from it? ? Paul, W9AC ? ? Yesterday, I ran my QDX for the first time off a 9V / 160 mA power adapter. You know, one of those things similar for charging your phone.
It was receiving properly, and I was even able to make some QSO's.
Today, I decided to use the same kind of power adapter, but this time a 9V / 1A version.
The QDX started out normally by flashing the led rapidly, then the led went off and smoke came from the QDX.
What in Earth may have happened here ?
I did not raise the voltage. The only thing that was new was that the adapter can supply more amps.
Any help would be appreciated.
Tnx,
73 Hans
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I always first plugs my power supply in the AC socket then after one minute plugs it in my QDX, expecting that any power on spikes are a matter of the past.
73?
Pierre?
FK8IH
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What can you tell us about your antenna SWR?? We assume you weren't connected to a dummy load since you were receiving and then transmitting.
Your small power adapter had very low current sourcing rating, so it was probably sagging voltage considerably.? If true, that means you were remaining lucky -- only because of your limited power input.
PA3CRZ >> I did not raise the voltage.
With the more robust power adapter you presumably reached at-or-near full voltage, and maybe overvoltage ... and then not so lucky.
Hopefully the only smoked parts were the final amplifier transistors.? Those are a relatively easy fix.
Don't damage your board trying to get parts out.? Start here with "Mr SolderFix":
This guy has very helpful videos on board repair.? Very reassuring, "you can do this" tutorials.? Worth your time to watch even if you don't learn anything new.
If you need to replace your final amplifier transistors, change them all.?They're cheap.? Cut those BS170s out with your diagonal cutters first.? Then you can remove the lead remnants one at a time, flux, soldering iron, tweezers.? If you have to remove any other multi-pin parts, like ICs, use desoldering alloy or a heat gun or the techniques in Mr SolderFix's video above.? Personally I favor desoldering alloy.? If an IC has a heat sink pad underneath, soldered to the board, the only way to remove it is with a heat gun.? But I don't think QDX has any parts like that.
Beware overvoltage on those plug-in power adapters.? You cannot trust them!? If you don't have a voltage-regulated, current-limiting power supply to do your initial testing with, buy a buck converter or a buck/boost converter and set it to a lower voltage than your rig's specified max input voltage.? It is very much worth it to treat your new radio gently.? 5 to 6 volts is a good place to start on a 9 volt max input transceiver.
Turn your power supply on first so it stabilizes, then connect your radio to turn it on.? Three people above have already mentioned that.? A lot of radios have been toasted by turning the power supply on with the radio already connected.? This is not a problem if you're running on batteries (with voltage less than the rig's max input voltage), but it can be a problem with many electronic power supplies.
Don't try for maximum output power.? Be happy with a watt or two less.? Lower the input voltage.
Don't use an automatic antenna tuner/matcher.? You will fry your finals, sooner or later.? I promise.
Good luck with your new rig!
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Pierre, the better approach is to power up the power supply or wall wart or whatever and measure its output voltage under no load conditions.? In my experience most wall warts are unregulated and will put out too high a voltage at no to light load and a more proper voltage at the current they are rated for.? Unless a particular power supply or wall wart is specified for rated voltage under no load conditions, you are taking a risk damaging your QXX.? The better ones also have specified current limiting or short circuit protection.? I'vee had good luck with CUI Inc series SWM12-N.? They come in different voltage output and are overvoltage, overcurrent, and short circuit protected. They are not inexpensive but they have good specifications.? I used the 12V one, a?SWM12-12-NH-P5, which cost $14.60 at Mouser.?
?
-Steve K1RF
------ Original Message ------
Date 7/22/2023 10:24:52 PM
Subject Re: [QRPLabs] Another QDX went up in smoke
I always first plugs my power supply in the AC socket then after one minute plugs it in my QDX, expecting that any power on spikes are a matter of the past.
73?
Pierre?
FK8IH
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I bought a 9V/1A wall power adapter planning to use it for my QDX, but it measured 10.8 volts under light load. Rather than risk my BS170s, I built a 9 volt series regulator using a LM317 instead, to drop my 13.8 volt supply down to a variable 7 to 10 volts instead. It's not as efficient as a buck regulator, but I don't need to filter out switching noise.
--
Larry. K0YPC
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My QDX is wired for 12V. To power it I use a 12V 2A SMPS brick salvaged from an old and decommissioned Netgear WiFi Router. The brick is compact, voltage regulation is excellent and I am not suffering switch mode noise. It works great!
JZ KJ4A?
I bought a 9V/1A wall power adapter planning to use it for my QDX, but it measured 10.8 volts under light load. Rather than risk my BS170s, I built a 9 volt series regulator using a LM317 instead, to drop my 13.8 volt supply down to a variable 7 to 10 volts instead. It's not as efficient as a buck regulator, but I don't need to filter out switching noise.
--
Larry. K0YPC
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Rich,
"Don't use an automatic antenna tuner/matcher.? You will fry your finals, sooner or later.? I promise."
Why do you say this? Is it because the ATU might slip up or make a poor match? Never heard of this.
tnx es 73,
Casey
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Casey,
ATUs go through multiple passes to find a match. Some of these passes have horrible SWR matches. Eventually it finds the better match and you are good to go. In addition, switching different combinations of C and L involves instances where there is a momentary open (or short) circuit. Either of these scenarios can present very high voltages to the finals. If they go over the voltage limit of your finals (~60 V for BS170), it can kill them nearly instantaneously unless you have some sort of protection for them. QRP Labs radios currently do not have any protections.?
Commercial radios have higher voltage limits and usually lower the power drastically when tuning. They also fold back power whenever they sense bad SWR. Things most QRP radios can't do. If you want to use an ATU, you should either drop power (usually by lowering input voltage significantly), or better yet, use a resistive/absorptive bridge while it is tuning.?
--
73, Dan? NM3A
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Yeah, what he said (about blowing finals with an automatic tuner).? Thanks, Dan NM3A.
Hey, I made an assumption that I'm embarrassed about.? Hans PA3CRZ did not actually say his QDX was transmitting when it blew its magic smoke.? If not transmitting, he'll have other cooked parts that he'll have to find and fix.? Maybe on the power bus etc.
Hans, if it helps, I bet most of us have seen the magic smoke.? I have.? I fried an AtMega328 microcontroller by probing around on a live radio, trying to figure something out.? That's when I learned how good it is to use low-temperature desoldering alloy, removing those 24-pin chips.? I had to replace it twice because the first replacement I put in was a damn clone chip and wouldn't work properly.? This was on a (tr)uSDX kit, not a QRP-Labs product.? Anyway, no board damage because the special alloy lets you remove your part with low temperature.
C'mon everybody, chime in and tell us about how you've smoked your radios (TVs, stereos, microwave ovens, ...) and had to deal with repairing your own goofs.? The dumber your mistake, the better the story.? This is how we learn, from our own mistakes and the mistakes of others.
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OK, but the statement was not explicitly about non-protected QRP radios, which made me think Rich was applying it more generally. There's always something new to learn, thought I'd missed something.
Yeah, best practice is always to lower power when tuning. You might not know when something goes wonky with an antenna and you are trying to tune into a short or open! Thanks for the clarification.
73
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I always tune my antenna manually with a transmatch fed by a NanoVna and when it's tuned I disconnect the NanoVna and connect the QDX.
73
Pierre
FK8IH
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Well, not just a component?
We summer in Maine and when closing up in the fall place the toaster in the microwave to keep critters and dust out.
This year I opened the place up myself ahead of my XYL and the clock was flashing so proceeded to set it and accidentally hit the on button. ?Only a couple of seconds went by but the toaster was indeed toasted (;-(
Duh,
John
We travel to Maine _._,_._,_
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After seeing the recurring reports of BS170 failures and the suspicion it is a VWSR
induced problem, I built a 6 dB PI attenuator to insert between the QDX and the
antenna tuner.? With a 6 dB attenuator in output during tuning, the worst Return
Loss that will occur is 12 dB, (VSWR of 1.7:1) even with an open or short on the
output side of the attenuator. For convenience I used a slide switch to bypass the
attenuator during? operation.
Regards
Chuck WD4HXG
On Jul 23, 2023, at 7:05 PM, Casey Bahr <hansva9@...> wrote:
OK, but the statement was not explicitly about non-protected QRP radios, which made me think Rich was applying it more generally. There's always something new to learn, thought I'd missed something.
Yeah, best practice is always to lower power when tuning. You might not know when something goes wonky with an antenna and you are trying to tune into a short or open! Thanks for the clarification.
73
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A very cheap solution, like the one proposed by Chuck:?
In tuning position the SWR is always under 2:1 and in operate position this tuning indicator is by-passed. I even use it with my Alexloop, a magnetic loop, the worst danger for a QDX!
73
Pierre
FK8IH
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Paul Christensen
KK4ITX John
Mike Besemer - WM4B
Pierre - FK8IH
Larry Reeves