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Re: QDX Success story
Yes, agreed!
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I think the fatal mechanism though is gate oxide punch through rather than avalanche, and that avalanche, if it is the lower voltage condition, actually somewhat protects the transistor by putting a higher failure energy demand on the inductor. The problem is, it can go either way. I have seen "walking wounded" failures of the BS170s where it is clear they are leaking drain current through a gate oxide pinhole and into the 74act08 driver chip. Things still work, but with degradation. It all depends on how big the punchthrough is and where it is. Large enough and the driver chip dies along with the BS170. JZ On Tue, Aug 8, 2023 at 9:31?AM mux_folder2001 <canthony15@...> wrote:
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Re: QDX Success story
开云体育
Yes, exactly. This was the case with my antenna during rainy weather as measured with my nanovna.?
So, the manufacturer of these VN0606 and TN0106 may be binning 100 volt parts as 60 volts, maybe due to some other parameter. Who knows.?
Anyway, I am hopeful that time will demonstrate that the diode is all that I need.?
One thing to note is that the idea that avalanche for even a very short time will kill the device is not always the case. It appears to me that the BS170 is being hammered at every EOT into 50 ohms.?
Tony
From: [email protected] <[email protected]> on behalf of John Z <jdzbrozek@...>
Sent: Tuesday, August 8, 2023 7:16 AM To: [email protected] <[email protected]> Subject: Re: [QRPLabs] QDX Success story ?
That's quite a punch, Tony!
Consider this: It gets worse when the load is at a low impedance.?
The drain currents go up sharply, and then so does the energy stored in the inductor, as the square of the current.?
That magnifies the danger of the low Z/ high SWR case.
JZ
On Tue, Aug 8, 2023, 8:40 AM mux_folder2001 <canthony15@...> wrote:
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Re: QDX Success story
That's quite a punch, Tony! Consider this: It gets worse when the load is at a low impedance.? The drain currents go up sharply, and then so does the energy stored in the inductor, as the square of the current.? That magnifies the danger of the low Z/ high SWR case. JZ On Tue, Aug 8, 2023, 8:40 AM mux_folder2001 <canthony15@...> wrote:
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Re: Fed Ex Vacation Hold
I saw a video recently where a UPS driver put the package on the porch, took a photo of it, then picked up the package and went back to the truck. People like that should do jail time. Jack, W8TEE
On Tuesday, August 8, 2023 at 08:44:44 AM EDT, Daniel Walter via groups.io <nm3a@...> wrote:
Jack, ?I had a similar problem with a new USPS driver. I actually DID run over the package. Fortunately it was a very sturdy item with very good packaging and no damage was done to the contents.? -- 73, Dan? NM3A |
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Re: QDX Success story
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From: [email protected] <[email protected]> on behalf of mux_folder2001 <canthony15@...>
Sent: Tuesday, August 8, 2023 6:36 AM To: [email protected] <[email protected]> Subject: Re: [QRPLabs] QDX Success story ?
Yes, that makes sense. I am still learning my new scope. I had it set to measure "Top" instead of "Maximum". You can see from the graticule scale that it is about 70 volts. BS170 drain picture attached (into dummy load, 9 volt build).
Tony
AD0VC
From: [email protected] <[email protected]> on behalf of John Z <jdzbrozek@...>
Sent: Tuesday, August 8, 2023 6:12 AM To: [email protected] <[email protected]> Subject: Re: [QRPLabs] QDX Success story ?
Tony,
My guess is that when you were running the BS170s and seeing a flat-topped 60V you were observing avalanche breakdown of the BS170 drain. Drain-gate oxide breakdown can also happen at that voltage. The TN0106 and VN0606 also have 60V breakdown specs, but the spec is a minimum and actual breakdown may occur at substantially higher voltage. In any case, you have seen first-hand what the inductive kick looks like and what damage it is capable of inflicting. JZ KJ4A On Tue, Aug 8, 2023 at 8:01?AM mux_folder2001 <canthony15@...> wrote: > > The diode is a good idea I think. This is based not only on simulation but on measurements I have made with my scope. > > In my case, the loss of two or three sets of BS170 in my two QDX units led me to try different transistors. I ran the other transistors without any failures for months. But I was curious why the BS170s would fail and the TN0106 and VN0606 would not. Yesterday I got a new scope that allows me to see transients and I decided to look at the QDX with VN0606 transistors in it. To my surprise, the glitch at the end of a transmission was over 120 volts measured at the center tap. The transistor drains were similar. The spike was 100ns wide at the 60 volt level. And this is into a dummy load. The transistors must just be capable of dealing with this. > > I then replaced the transistors with BS170s and discovered another surprise. The spike was below 60 volts and had a broad flat (but ragged looking) top. > > Then I added the commutating diode and the spikes were gone. > > Right now my theory is that the BS170s are operating in a "make before break" mode which minimizes the di/dt. The VN0606 (and TN0106) might be in the "break before make" mode. The specific operating conditions might possibly allow the circuit to move between these two cases and the BS170s are just not capable of handling the over-voltage spike while the other transistors can. Just a theory mind you. I have not tried yet to make measurements to verify this. Prior to these measurements, I was thinking that the opposite would be the case, thus explaining why the VN0606/TN0106 did not fail. > > In any case, I am now running with BS170s again but with the diodes installed. We shall see how long this lasts. > > Tony > AD0VC > > ________________________________ > From: [email protected] <[email protected]> on behalf of John Z <jdzbrozek@...> > Sent: Monday, August 7, 2023 6:14 AM > To: [email protected] <[email protected]> > Subject: Re: [QRPLabs] QDX Success story > > Simulations are here: > > /g/QRPLabs/message/105254 > > JZ > > On Mon, Aug 7, 2023 at 8:07?AM John Zbrozek <jdzbrozek@...> wrote: > > > > Hi Pierre, > > > > The diode simply is in parallel with the 47uH inductor L14, with the > > orientation shown in the photo provided by Paul W9AC. Cathode towards > > the power supply connection, anode to the transformer center tap. > > Any of the diodes he mentioned? (1N4448, 1N4148, 1N914) will do a fine > > job of absorbing the end-of-transmission voltage spike it produces. > > I have used a 1N914. > > > > /g/QRPLabs/message/105256 > > > > Here you can see simulations with and without the diode present. > > > > On another thread, Evan, Hans and I explore the ability of QDX to > > withstand SWR. It seems to have a reputation for SWR intolerance but I > > think there is a case that the problem may actually be as described > > above. > > > > /g/QRPLabs/message/106759 > > > > Regards, JZ KJ4A > > > > On Mon, Aug 7, 2023 at 7:46?AM Pierre FK8IH <jb.gallauziaux@...> wrote: > > > > > > Could you please elaborate: what diode, how did you connect it? A handmade schematic and a photo would be nice. > > > 73 > > > Pierre > > > FK8IH > > > > > > > > > |
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Re: Fed Ex Vacation Hold
Those of you who have had good experiences with Fed Ex being responsive to your delivery instructions owe your local Fed Ex a big hug.? I have found my local Fed Ex to be impervious to requests.
On the good side.? I know what my next QRPlabs purchases will be, and I know that there is no chance that I will build them within six months.? So I am going to place orders now via the slow but reliable postal service. 73 Chris W2BPL -- Chris / W2BPL |
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Re: QDX Success story
开云体育
Yes, that makes sense. I am still learning my new scope. I had it set to measure "Top" instead of "Maximum". You can see from the graticule scale that it is about 70 volts. BS170 drain picture attached (into dummy load, 9 volt build).
Tony
AD0VC
From: [email protected] <[email protected]> on behalf of John Z <jdzbrozek@...>
Sent: Tuesday, August 8, 2023 6:12 AM To: [email protected] <[email protected]> Subject: Re: [QRPLabs] QDX Success story ?
Tony,
My guess is that when you were running the BS170s and seeing a flat-topped 60V you were observing avalanche breakdown of the BS170 drain. Drain-gate oxide breakdown can also happen at that voltage. The TN0106 and VN0606 also have 60V breakdown specs, but the spec is a minimum and actual breakdown may occur at substantially higher voltage. In any case, you have seen first-hand what the inductive kick looks like and what damage it is capable of inflicting. JZ KJ4A On Tue, Aug 8, 2023 at 8:01?AM mux_folder2001 <canthony15@...> wrote: > > The diode is a good idea I think. This is based not only on simulation but on measurements I have made with my scope. > > In my case, the loss of two or three sets of BS170 in my two QDX units led me to try different transistors. I ran the other transistors without any failures for months. But I was curious why the BS170s would fail and the TN0106 and VN0606 would not. Yesterday I got a new scope that allows me to see transients and I decided to look at the QDX with VN0606 transistors in it. To my surprise, the glitch at the end of a transmission was over 120 volts measured at the center tap. The transistor drains were similar. The spike was 100ns wide at the 60 volt level. And this is into a dummy load. The transistors must just be capable of dealing with this. > > I then replaced the transistors with BS170s and discovered another surprise. The spike was below 60 volts and had a broad flat (but ragged looking) top. > > Then I added the commutating diode and the spikes were gone. > > Right now my theory is that the BS170s are operating in a "make before break" mode which minimizes the di/dt. The VN0606 (and TN0106) might be in the "break before make" mode. The specific operating conditions might possibly allow the circuit to move between these two cases and the BS170s are just not capable of handling the over-voltage spike while the other transistors can. Just a theory mind you. I have not tried yet to make measurements to verify this. Prior to these measurements, I was thinking that the opposite would be the case, thus explaining why the VN0606/TN0106 did not fail. > > In any case, I am now running with BS170s again but with the diodes installed. We shall see how long this lasts. > > Tony > AD0VC > > ________________________________ > From: [email protected] <[email protected]> on behalf of John Z <jdzbrozek@...> > Sent: Monday, August 7, 2023 6:14 AM > To: [email protected] <[email protected]> > Subject: Re: [QRPLabs] QDX Success story > > Simulations are here: > > /g/QRPLabs/message/105254 > > JZ > > On Mon, Aug 7, 2023 at 8:07?AM John Zbrozek <jdzbrozek@...> wrote: > > > > Hi Pierre, > > > > The diode simply is in parallel with the 47uH inductor L14, with the > > orientation shown in the photo provided by Paul W9AC. Cathode towards > > the power supply connection, anode to the transformer center tap. > > Any of the diodes he mentioned? (1N4448, 1N4148, 1N914) will do a fine > > job of absorbing the end-of-transmission voltage spike it produces. > > I have used a 1N914. > > > > /g/QRPLabs/message/105256 > > > > Here you can see simulations with and without the diode present. > > > > On another thread, Evan, Hans and I explore the ability of QDX to > > withstand SWR. It seems to have a reputation for SWR intolerance but I > > think there is a case that the problem may actually be as described > > above. > > > > /g/QRPLabs/message/106759 > > > > Regards, JZ KJ4A > > > > On Mon, Aug 7, 2023 at 7:46?AM Pierre FK8IH <jb.gallauziaux@...> wrote: > > > > > > Could you please elaborate: what diode, how did you connect it? A handmade schematic and a photo would be nice. > > > 73 > > > Pierre > > > FK8IH > > > > > > > > > |
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Re: #qmx QMX receive appears slightly deaf, birdies
#qmx
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Re: #qmx QMX receive appears slightly deaf, birdies
#qmx
Voltages good then. Every time I've had an Rx issue I've had bad voltages there. One required a new multiplexor (because of excess probing) and the other needed the trifilar toroid rewound. I did have one where the soldering on the BPF caps was not making correct connections. I had to reflow the solder on those caps... Double check T507. I might start with a signal at the antenna and start tracing back through the receiver. Maybe someone else has another idea...
-mike/w1mt |
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Re: #qmx QMX receive appears slightly deaf, birdies
#qmx
R401/R402 and C406 are designed to provide a 2.5v bias to the signals passing through the demodulator? switches (IC 403) and the? following amplifies that all need non-zero dc signals.? On my QMX C406 was damaged and replaced before powering up.??
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Re: QDX Success story
Tony,
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Show quoted text
My guess is that when you were running the BS170s and seeing a flat-topped 60V you were observing avalanche breakdown of the BS170 drain. Drain-gate oxide breakdown can also happen at that voltage. The TN0106 and VN0606 also have 60V breakdown specs, but the spec is a minimum and actual breakdown may occur at substantially higher voltage. In any case, you have seen first-hand what the inductive kick looks like and what damage it is capable of inflicting. JZ KJ4A On Tue, Aug 8, 2023 at 8:01?AM mux_folder2001 <canthony15@...> wrote:
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Re: #qmx QMX receive appears slightly deaf, birdies
#qmx
The voltage at the top of C406 (feeding T401)? is 2.5v, exactly as expected.
I've checked voltage levels around pins 3, 4, 5 of IC402?and are all at 2.5v, also as expected. I can't see any rf signals aournd IC402 with my 'scope only having 10mV sensitivity (even with the the signal generator output turned up). What other probing would you suggest? I did wonder whether there was an issue with Q508 or surrounding circuitry, but that would surely show up with the Audio filter sweeps? Cheers, Dave M0JTS |
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Re: Fed Ex Vacation Hold
I ordered a Hantech 200MHz scope and FedEx delivered it by leaving it in front of our detached garage, which made it invisible from the house. Later that evening after a two hour torrential rain, I started to back my car out of the garage and, for some unknown reason, I stopped, got out of the car, and looked behind it. There was my soggy box that narrowly escaped being pancaked by my car. Fortunately, the internal styrofoam clam shell packaging kept the scope dry, but Fed Ex got an earful about their delivery. From then on, every package from Fed Ex has been left on the back porch. Jack, W8TEE
On Tuesday, August 8, 2023 at 07:18:55 AM EDT, Chris / W2BPL <kwaj.speedo@...> wrote:
I used that Fed Ex feature when I found myself in a similar situation with my QCX mini shipment. They just ignored it. ?When I returned home I found it sitting slightly soggy in the driveway having been delivered on the day predicted when it was shipped. Maybe you will have better luck. 73 Chris W2BPL -- Chris / W2BPL |
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Re: QDX Success story
开云体育
The diode is a good idea I think. This is based not only on simulation but on measurements I have made with my scope.
In my case, the loss of two or three sets of BS170 in my two QDX units led me to try different transistors. I ran the other transistors without any failures for months. But I was curious why the BS170s would fail and the TN0106 and VN0606 would not. Yesterday
I got a new scope that allows me to see transients and I decided to look at the QDX with VN0606 transistors in it. To my surprise, the glitch at the end of a transmission was over 120 volts measured at the center tap. The transistor drains were similar. The
spike was 100ns wide at the 60 volt level. And this is into a dummy load. The transistors must just be capable of dealing with this.
I then replaced the transistors with BS170s and discovered another surprise. The spike was below 60 volts and had a broad flat (but ragged looking) top.?
Then I added the commutating diode and the spikes were gone.?
Right now my theory is that the BS170s are operating in a "make before break" mode which minimizes the di/dt. The VN0606 (and TN0106) might be in the "break before make" mode. The specific operating conditions might possibly allow the circuit to move between
these two cases and the BS170s are just not capable of handling the over-voltage spike while the other transistors can. Just a theory mind you. I have not tried yet to make measurements to verify this. Prior to these measurements, I was thinking that the opposite
would be the case, thus explaining why the VN0606/TN0106 did not fail.?
In any case, I am now running with BS170s again but with the diodes installed. We shall see how long this lasts.
Tony
AD0VC
From: [email protected] <[email protected]> on behalf of John Z <jdzbrozek@...>
Sent: Monday, August 7, 2023 6:14 AM To: [email protected] <[email protected]> Subject: Re: [QRPLabs] QDX Success story ?
Simulations are here:
/g/QRPLabs/message/105254 JZ On Mon, Aug 7, 2023 at 8:07?AM John Zbrozek <jdzbrozek@...> wrote: > > Hi Pierre, > > The diode simply is in parallel with the 47uH inductor L14, with the > orientation shown in the photo provided by Paul W9AC. Cathode towards > the power supply connection, anode to the transformer center tap. > Any of the diodes he mentioned? (1N4448, 1N4148, 1N914) will do a fine > job of absorbing the end-of-transmission voltage spike it produces. > I have used a 1N914. > > /g/QRPLabs/message/105256 > > Here you can see simulations with and without the diode present. > > On another thread, Evan, Hans and I explore the ability of QDX to > withstand SWR. It seems to have a reputation for SWR intolerance but I > think there is a case that the problem may actually be as described > above. > > /g/QRPLabs/message/106759 > > Regards, JZ KJ4A > > On Mon, Aug 7, 2023 at 7:46?AM Pierre FK8IH <jb.gallauziaux@...> wrote: > > > > Could you please elaborate: what diode, how did you connect it? A handmade schematic and a photo would be nice. > > 73 > > Pierre > > FK8IH > > |
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Re: Fed Ex Vacation Hold
We have a table on the front porch, and all our delivery folks have figured out that?it's a Good Idea to put packages on the table. ? N6OTQ On Tue, Aug 8, 2023 at 6:18?AM Chris / W2BPL <kwaj.speedo@...> wrote: I used that Fed Ex feature when I found myself in a similar situation with my QCX mini shipment. |
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Re: Fed Ex Vacation Hold
I used that Fed Ex feature when I found myself in a similar situation with my QCX mini shipment.
They just ignored it. ?When I returned home I found it sitting slightly soggy in the driveway having been delivered on the day predicted when it was shipped. Maybe you will have better luck. 73 Chris W2BPL -- Chris / W2BPL |
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Re: Short circuit in buck converter QMX
Do NOT try to move a SMD device without heating all the pads. You will
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break something. Go to the local hobby/hardware store and get a heat embossing tool. Mine cost me 10USD from amazon. Or use a low temp alloy like from ChipQuik to remove the device then clean and reinstall. -mike/w1mt On Tue, Aug 8, 2023 at 5:45?AM Crni Mrki, DK4BN <crnimrki@...> wrote:
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Karl
Ed Oxer, W8EO
jjpurdum
Chris / W2BPL
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