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#qdx QDX and a smoked BS170
#qdx
Hi everyone. I need a little help if you could.
I've had my QDX v4 (12volt) up and running for quite some time with no issues. Yesterday I was doing ft8 on 20m and heard a pop and caught a whiff of magic smoke. The LED light went out. After investigating I found that one of the bs170's had burned popped open. Maybe I had a bad swr at the moment, I'm not sure.? I got busy replacing the blown fet and hooked everything back up. I noticed that the frequency and bands weren't changing and the audio was strange with no perceived signals.? I measured the current draw on power up RX and found it to be about 700ma. I removed all 4 bs170's and the current didn't change. I then removed IC5 and now the current draw is around 900ma.? I'm at a bit of a loss of what to check next. Can anyone suggest some test points with expected voltage or resistance levels? Many thanks! James Shrum - AB9LM |
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Re: Theory of operation (circuit theory)?
Hi Peter There aren't yet full theoretical notes. You can find some stuff in my FDIM 2023 conference proceedings article at and a lot of the design is similar to QDX which is described in some detail in it's manual at . Despite this various material there are still some gaps and a detailed explanation does need to be penned... But there's a lot to do and it hasn't been done yet... 73 Hans G0UPL On Sun, Feb 25, 2024, 4:50?PM Peter AA2VG <Petersdeluca@...> wrote: Hi. Last evening I finished assembling my QMX and loaded the firmware. Today I¡¯ll see how she performs. Having built the QCX years ago, I keep searching for the alignment instructions but since there were no adjustable pots in the build (except for the LCD screen) can I assume there is no alignment?? |
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Re: Noise around 150Hz on digi mode with my
#qmx
Hi Hans, ? Thanks a lot, I ignore that feature exists on WSJTX. ? 73, |
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QMX Diagnostic Power Out Vs Meter
My QMX Rev 2 Putty Diagnostic is showing <.5w with a voltage of 10.1. ?Supply voltage into the QMX was 11.9. ?My SWR/power meter is a good CB unit that shows 2watts on 80m, and about 2.5 watts on the other bands. This CB meter should differentiate between .5 and 2.5 watts I would think.
-- |
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Theory of operation (circuit theory)?
Hi. Last evening I finished assembling my QMX and loaded the firmware. Today I¡¯ll see how she performs. Having built the QCX years ago, I keep searching for the alignment instructions but since there were no adjustable pots in the build (except for the LCD screen) can I assume there is no alignment??
It is noted in the assembly manual that the circuit theory is found in another location. Can anyone tell me where I can find the circuit theory? Is there any alignment needed other than adjusting the coils on the band pass filters? I appreciate the engineering that went into getting all the functionality into such a small and compact package. 72 Peter/AA2VG |
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Re: USB Powered QDX ?
Hi Hans,
Thanks again for the great QRP Labs products. You're right about me getting my wires crossed somewhat. I was thinking about the following QMX issue when I made the comment:?. I was also thinking of the 1.5V SMPS transmit bias circuit in the QDX. I had an unexpected failure of my QDX during initial testing of the diode modification I described. The failure occurred while powered by 5V from the USB cable and then connecting 12V, and the symptoms were similar to what Gunnar explained in his original post. I believe it was a Rev 4 QDX. It has been a few months since this happened, and it sounds like I need to revisit this scenario. The initial intent of the diode solution was to allow 5V operation via the existing USB connection, while also allowing 12V operation when desired. This solution seems to work reliably as long as, when your want to run full power, you connect 12V first. |
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Re: QMX early use fail - dynamic vdd signature
Hi Steve,
This is not the typical cpu VDD short to ground behavior. ?Check with a DVM in continuity mode for VDD shorted to ground on the main board without any other boards plugged into it. ?You can trace where the short is (if there is one) with a milliohm meter. ?If you can¡¯t find it, I¡¯m glad to take a look. ?My backlog for repairs is small. 73, Jeff W1NC |
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Re: QMX PTT Not Working
Hi,
you can also test it with the Diode function if your AVO has it which operate at a higher voltage. But the simplest test if a GND PTT line at the tip of connector is working is if you - enable both the +5V and the GND PTT in the configuration menu and - then measure the voltage between the tip and ring. It should be around +5V. -- 73 Bojan S53DZ |
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Re: USB Powered QDX ?
Hi William,
The product that AJ8S suggests is a Buck Boost converter.? ?It converts the input power and current to the set voltage output as long as it is within the range of the device.? It will maintain the 12 volts to the point where the battery can not supply enough power to convert to the higher voltage. 73 Evan AC9TU |
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Re: 10W HF Linear Power Amplifier
#10W_PA
On 25/02/2024 09:07, timo.vandermerwe@... wrote:
I measure the ohms between *Ground and In* as well as *Ground and Out*. To my surprize it is around 0.3 ohms - basically a dead short.To DC. If you look at the schematic you see input and output has transformers. DC resistance very low. But reactance to RF is not low. 73 Alan G4ZFQ |
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Re: QMX PTT Not Working
Hi Jim.?
I had made the same assumption as you when I first tested my QMX PTT out after firmware 017 was released and I installed the jumper as you have done. But Hans explained that the circuit in the QMX sinks an external current, and a multi-meter can't be used to simply test tip to ground. It doesn't work that way.? The device you want to trigger needs to supply some (low) voltage and current, and the QMX in the tip to ground configuration, will sink that current, looking like a short to the external device (but not to an ohm meter).? In my case I need to trigger an external TX RX switch which allows my SDR Play receiver to share the same antenna that QMX uses. That device supplies 4v and a few mA of current (I forgot the amount) to that lead coming from the QMX, and the QMX effectively shorts that line (tip to barrel of PTT out) and triggers the device. So, the QMX PTT out does in fact, work properly (once the board has the jumper installed, and the configuration settings are enabled for each band, as you've already done). It can't be tested with only an ohm meter, however.? It can be tested using an external power source (3.2v for a typical LED) and an LED with current flowing through (in series with) PTT out tip and barrel. In QMX RX mode, the LED will be bright, when it goes to TX the LED will significantly dim or go off. (when configured as grounded on TX)? So it does work as advertised, just not as both you and I assumed it would work.? 73 Roy - KI0ER? |
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10W HF Linear Power Amplifier
#10W_PA
I measure the ohms between Ground and In as well as Ground and Out.? To my surprize it is around 0.3 ohms - basically a dead short.? What resistance would be expected here.? The amp seems to start-up fine and can be adjusted for bias.?
73 de ZR6TM Timo?? |
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Hi Ludwig Frequency calibration hasn't been implemented yet. It's not high priority because QMX has a high performance 25 MHz TCXO as standard, for it's frequency reference. Unlike QCX where it's an option. The 25 MHz TCXO is normally within a few Hz anyway.? 73 Hans G0UPL On Sun, Feb 25, 2024, 12:59?AM <DH8WN@...> wrote: Hello, I have a question. |
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Re: QMX Audio Noise when switching to Digital mode
Or it might be no issue at all. The volume level on digital is just much higher than when on CW. Perhaps something I need to add an adjustment for. So this could be NO issue at all, just an expectations thing? 73 Hans G0UPL On Sun, Feb 25, 2024, 3:59?AM <w6csn@...> wrote: My original post title may be misleading. The symptom I¡¯m seeing is the noise is present continuously when Digi mode is enabled, not just during the switching transitions. |
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Re: Noise around 150Hz on digi mode with my
#qmx
Hi Quentin This is a WSJT-X feature called "Flatten", which is intended to compensate for the imperfect passband of some crystal filters etc (with suitable calibration). On QMX the passband is already flat, it's a DSP filter and very flat. You need to switch off "Flatten". It's a checkbox at the bottom of the waterfall display screen of WSJT-X. 73 Hans G0UPL On Sun, Feb 25, 2024, 9:14?AM Quentin VA4HSW/F4HSW via <qrp.le8b2=[email protected]> wrote: Hi, |
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Re: USB Powered QDX ?
Hi Howard > BE AWARE! There is a known > "issue" with the QDX switching > regulator when rapidly > transitioning from a lower > voltage to a higher voltage You're mixing up with QMX. QDX doesn't have switching regulators. There isn't any such issue on QDX... 73 Hans G0UPL On Sun, Feb 25, 2024, 4:11?AM Howard <howard@...> wrote: I have not used a 5V to 12V boost converter, but I have added a couple diodes to my QDX to pull 5V from the QDX USB data port and apply it to the +12V and VCC rails to power the rest of the radio. Since the QDX transmit power is relative to the input voltage, powering it will 5V results in about 100mW of transmit power. I have made contacts at 1000 miles using JS8Call with this modification. Powering the QDX with 5v has been discussed in other posts in the past. |
Barb WB2CBA
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