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QDX - No RF output, Tx line stays low
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I assembled my QDX this week, built for a 9v supply. ?All went well, interfaced with WSJT-X v2.5.1 on Toshiba laptop running up-to-date Windows 10. ?In WSJT-X under settings, the Audio tab shows ¡°Digital Audio Interface (QDX Transceiver)¡± as present for both Input and Output, and selected. ?The Radio tab shows Rig as Kenwood TS-480, CAT Control over Serial Port COM3, and PTT method CAT. ?Test CAT works, Test PTT puts QDX into Transmit mode it appears, with the LED?triple light flash mode on the QDX. ?The receiver works fine on all four bands. ?BUT there is no RF output at all. ?Putting the QDX into transmit with Test PTT in the Radio tab, or Enable Tx, or Tune, causes the LED to flash, but no RF output. ?Scoping the unit out, I see no signal on the gates of the BS170 transistors. ?Examining IC5, the 74ACT08, I see CLK0 at pins 9 and12 and CLK1 at pins 1 and 4 both present at expected levels. BUT the Tx line is low in both Receive and Transmit modes. ?So the outputs on pins 8/11 and 3/6 are always low, thus no drive to the BS170s. Resistance checks on the Tx line with the QDX not powered show 10K Ohms to the +5 volt rail (through R5) and 12.5K Ohms to ground. ?So there does not appear to be a short holding Tx low. ?Looks like something is pulling Tx low at all times, in both Receive and Transmit modes. ?Hard for me to see how it could be anything other than the microcontroller. ?Has anyone else experienced this with the QDX? ?I installed firmware 1.01a and the EEPROM.QDX and that made no difference.
73, Ben ?K0IKR |
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Hi Ben? See my message earlier about 1.01c. And install 1.01c. The diagnostics on the status LED will help understand what's going on.? The TX signal on the schematic is more of a "key down". It won't happen until the QDX receives an audio stream.? 73 Hans G0UPL http://qrp-labs.com -------- Original message -------- From: "Ben Bangerter, K0IKR via groups.io" <bwbangerter@...> Date: Sat, Nov 13, 2021, 12:06 AM To: [email protected] Subject: [QRPLabs] QDX - No RF output, Tx line stays low I assembled my QDX this week, built for a 9v supply. ?All went well, interfaced with WSJT-X v2.5.1 on Toshiba laptop running up-to-date Windows 10. ?In WSJT-X under settings, the Audio tab shows ¡°Digital Audio Interface (QDX Transceiver)¡± as present for both Input and Output, and selected. ?The Radio tab shows Rig as Kenwood TS-480, CAT Control over Serial Port COM3, and PTT method CAT. ?Test CAT works, Test PTT puts QDX into Transmit mode it appears, with the LED?triple light flash mode on the QDX. ?The receiver works fine on all four bands. ?BUT there is no RF output at all. ?Putting the QDX into transmit with Test PTT in the Radio tab, or Enable Tx, or Tune, causes the LED to flash, but no RF output. ?Scoping the unit out, I see no signal on the gates of the BS170 transistors. ?Examining IC5, the 74ACT08, I see CLK0 at pins 9 and12 and CLK1 at pins 1 and 4 both present at expected levels. BUT the Tx line is low in both Receive and Transmit modes. ?So the outputs on pins 8/11 and 3/6 are always low, thus no drive to the BS170s. Resistance checks on the Tx line with the QDX not powered show 10K Ohms to the +5 volt rail (through R5) and 12.5K Ohms to ground. ?So there does not appear to be a short holding Tx low. ?Looks like something is pulling Tx low at all times, in both Receive and Transmit modes. ?Hard for me to see how it could be anything other than the microcontroller. ?Has anyone else experienced this with the QDX? ?I installed firmware 1.01a and the EEPROM.QDX and that made no difference. |
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Hello Ben,
I had the same issue and after Hans's explanation on what is going on in the software I switched to a different platform (went from Windows to Raspberry Pi) and the TX signal appeared.? As stated in Hans's message, he has updated the firmware to let us know what is going on in the software. A quick summary of my transmit issue was the USB link with the Windows10 computer was dropping out and a tone was not being sent to the QDX so it never went into a signal transmit, it was just ready to transmit. Note, that computer still does not link properly with the QDX.? I have other computers running Windows10 that do.? The issue is the USB link dropping. 73 Evan AC9TU PS; be careful probing around the PA MOSFETs.? A brief twitch and both MOSFETs on one side of the push-pull amp let out the smoke.? It also took out IC5, the 74ACT08 PA Driver.? Asl me how I know.? Let's say I have practice now with repairing the full transmitter power chain.? The QDX is a very small device for this 69-year-old body to handle.? Extra care is required on my part. |
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Hans and Evan. Thank you for the quick replies. ?I had not seen that mention of a version 1.01c. ?I will do that. ?I have a Windows 10 laptop and a WinXP desktop. ?Yeah, I know - dated, but the best OS Microsoft ever put out. Used for film scanning and image processing. ?This may lead me to get an RPi and display I suspect. ?I was very cautious probing the QDX. ?These surface mount devices with small footprints make troubleshooting exceedingly difficult! ?And Evan: ?Oh to be 69 again. Ah, youth! ?I just turned 80.
73, Ben ?K0IKR |
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On Fri, Nov 12, 2021, at 04:10 PM, Ben Bangerter, K0IKR wrote:
This may lead me to get an RPi and display I suspect.Ben, I use one of my older flat-screen TVs with HDMI input for the Raspberry Pi (RPi) monitor and speakers.? The one that I have is 24" 1080p so nice high resolution for the RPi.? The sound is sent over the HDMI cable.? Suggest a Ras[berry Pi 4, though the 3 can do WSJT-X, just a little slower.? I bought a Cana Kit that included the heatsink as part of the case.? You do need to keep the processor cool, and this is the best non-fan version that I found.? You will need a USB mouse and keyboard as well. 73 Evan AC9TU |
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I finished the QDX today and experienced the finals failure. Wound the transformer for 12 volts, used a LIOn battery at 12.2 volts. Receive worked incredibly well. Transmit tested with a dummy load. Output was about 1 watt on 20 m and 40m but no output on 80. I measured the voltage on the finals and was 12 v on all in receive. Next time I transmitted there was no power and that ominous smell started being emitted. A visual inspection found that R37 was missing. Apparently knocked off rather than unsoldered by mistake. I¡¯m not sure a bypass capacitor would have that much effect on output power or failure. I will disconnect the 12 v feed to the finals and see if the IC5 is also dead.?
Conditions: 12 ?v? Win10 Wsjtx Stock firmware? -- Jginaz |
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Update on the debug. First replaced C37 with .1uf. Inserted a 560 ohm resistor in series with L14. Measured the final¡¯s gates with a scope. Q8,10 had squashed signal,?Q9, 11 had 5 v square wave. The drain of these also looked ok with a sawtooth wave. Q8,10 drain looked bad. Removed Q8,10 remeasured and now tx signal never goes high. Loaded latest firmware and I¡¯m getting the 3 quick flashes but no tx signal. Will likely replace IC5 but I need to think about how to remove while the replacement?part is in transit.?
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Jay On Saturday, November 13, 2021, 5:19 AM, Steve via groups.io <qed28@...> wrote:
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Jginaz |
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John, thanks for the tip it¡¯s coming tomorrow.
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Jay On Saturday, November 13, 2021, 3:30 PM, John AE5X <ae5x@...> wrote:
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Jginaz |
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I resolved my problem today, not a hardware problem (the rabbit hole I went down initially) but a computer issue. ?Setting both the computer audio output and the power level in WSJT-X at maximum, and trying a few different USB cables, I got RF output: ?80M, 5.6W; 40M, 5.2W; 30M,5.5W; 20M, 3.6W. ?I had a couple QSOs on 20M, and saw many spots on PSKReporter. ?I found it was necessary to connect the USB cable between the QDX and the computer (Win10 laptop) BEFORE powering on the QDX (9V) to get the computer to recognize the rig. ?I found it was sometimes necessary to repeat the process of turning on the QDX then launching WSJT-X a couple times to establish a connection. ?I suspect it is more an issue with this particular PC than with the QDX. ?So today zi am a happy camper!
73, Ben ?K0IKR |
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Hi Ben,
Congratulations on finding the problems and the QSO. FYI, I too have the issue of needing to power cycle the QDX a number of times to get a connection.? I have the issue on more than one Windows PC, so it is a compatibility question with Windows.? As Hans has stated he has not done extensive testing with Windows as he has a long startup situation with his current Windows PC.? I was given a tip to disable the suspend function for the USB connections.? That may have helped in reducing the reoccurrence of the problem, but I was able to connect prior to making the change.? The tip is in this message from Gregg Myers: /g/QRPLabs/message/74548 I have found that after I get the QDX connected it does work well. 73 Evan AC9TU |
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Hello Jay,
FWIW, I had to replace IC5 after determining that it was not working.? I removed the 4 BS170 MOSFET finals and then tested the output of IC5 to the gate pads.? One side had nice square wave signals, the other did not.? IC5 was bad, probably taken out when the finals became resistors and not MOSFETs anymore. To repair IC5, I simply cut off all of the leads of IC5 with a fine diagonal cutter right next to the IC.? Clip parallel to the chip side to reduce any strain on the pad.? ?I then cleaned off the left behind leads with my iron and solder wick. Then installed the 74ACT08 replacement.? I verified that the drives to the gate pads were correct (On the first test I found that one of the output leads of IC5 had a cold joint) and then installed the BS170s.? I would have had issues if I had not found the joint issue with one of the pins on IC5. You might want to replace all 4 of the BS170 MOSFETs while you are at it.? The ones that check out as OK could be weakened, and they are not that expensive.? Better to start with a fresh set of tested BS170s. If you do decide to use Chip Quick be sure to clean off all of the solder after the removal of the IC as per the instructions.? That solder is very brittle and will cause long-term issues if not removed properly before installing the new part. Good luck with the repair. 73 Evan AC9TU |
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Thanks for the advice, Evan. How did you clear the solder from the BS170 holes? I tried wick and was only successful with 2 holes. I didn¡¯t want to be too aggressive as the pads were starting to lift.?
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Jay On Saturday, November 13, 2021, 9:38 PM, Evan Hand <elhandjr@...> wrote:
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Jginaz |
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Jay,
I have found a tool like this to be the best: Note: This is not the exact tool that I have, as I cannot find the link that I used a couple of years ago. I find that positioning the hole of the tool right over the lead sticking through, putting slight pressure on the lead until I feel it give a little, then try to center and then release the bulb.? Be sure to squeeze the bulb with you thumb before you put it over the board.? I have an old box that I keep beside the work surface that I pump the bulb a couple of times to clear before going to the board to remove the part.? Again, be sure to squeeze the bulb away for anything that can be damaged, and holding the bulb squeezed, place it on the joint to be processed. Here is the video that I used to learn how to do it: I have not had a solder pad lift using this tool and technique.? Your mileage may vary. 73 Evan AC9TU |
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It may seem counterintuitive, but this tool works better if there is plenty of solder on/in/around the hole. The reason is that with more solder, there is more contact with the tip of the desoldering tool, so more heat flows all the way through the via to the other side and melts the solder on the other side too, which is critical for a good clear. You really want to have to do it only once, otherwise too much pressure and the high (420C) temperature will damage &/or lift the pad, so be brave, add enough extra solder to cover the entire flat surface of the tool tip.
This technique of adding a little extra solder is especially important if the hole you're trying to clear is on the ground plane, which will do its darnedest to pull all the heat away and prevent a successful clear.? As with all soldering, make sue the board is properly restrained and not wobbling around, plan your angle of approach, make sure you don't touch plastic parts with the shaft of the tool, and be careful not to slip and remove surface mount parts instead. -- Julian, N4JO. |
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Hi Evan? I did test on Windows. It takes a while to boot up but if you're patient Win10 does work OK. I find it frustrating but it works.? I didn't have any problems connecting or operating QDX from Windows. Quite a few reports from other users here also confirm the same. So Windows works... But then again other people are having problems with it. So it seems not all Windows systems are equal.? 73 Hans G0UPL http://qrp-labs.com -------- Original message -------- From: Evan Hand <elhandjr@...> Date: Sun, Nov 14, 2021, 7:21 AM To: [email protected] Subject: Re: [QRPLabs] QDX - No RF output, Tx line stays low Hi Ben, |
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Hi Hans,
I still do not know what the underlying issue is with the two Windows 10 systems that I have tried so far.? I can say that I can now reliably connect and use the QDX on one of them, it may just take 3 restarts to get it to work.? I do not have that issue with the Raspberry Pi system unless I first have the issue with one of the Windows systems.? So it seems to be a state issue in the QDX that can take 3 power cycles to resolve.? Once resolved it does work well on both systems.? Maybe it has something to do with the upgrade system in the QDX.? Not sure that I have the tools to work this one out. As long as I know about the 3 power cycle fix, I see it only as a nuisance.? If you are careful on the first startup after a power down it does not happen.? The sequence seems to be the thing: 1 Connect the antenna and USB cable 2 Be sure the PC is on and ready to go 3 Connect the QDX power 4 Then start whatever program you want to connect to. If the program will not work, then power off the QDX, reapply power, and try again.? You may have to repeat this a second time to get it to work.? If I do need to start again, I always start with the terminal connection to ensure it is not in update mode.? I also ensure that I always exit out of terminal mode before closing the PuTTY program.? A power switch on the QDX would have made this easier.? I am looking into modifying the case and board to see if I can squeeze one in.? I have two extra to experiment with as two of our builders opted not to build the kit. 73 Evan AC9TU |
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Hi Evan To know where QDX is in firmware update mode or not, you only need to look at the status LED. A slow continuous flash means firmware update mode.? In power up in normal operating mode the status LED flickers quickly for 5 seconds. During this time if you disconnect power and reconnect, it will enter firmware update mode.? There are a lot of posts and I can't refer to it precisely but I seem to remember someone posting their sequence of operations, their recipe for success... That included waiting for the status light flickering to stop and become steady. In fact this is not necessary. QDX operates in those first 5 seconds, there is no need to wait for connecting PC etc. You don't need to wait for the steady LED.? 73 Hans G0UPL http://qrp-labs.com -------- Original message -------- From: Evan Hand <elhandjr@...> Date: Sun, Nov 14, 2021, 9:36 AM To: [email protected] Subject: Re: [QRPLabs] QDX - No RF output, Tx line stays low Hi Hans, |
Julian N4JO
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