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Re: AGC for the QMX?
Hi Mike, What I meant to point out is that, when you have two or more stations within the receiver bandwidth (and you are interested in one, of course), and if you have AGC on that receiver, the receiver gain will be dictated by the signal strength (and fading fluctuation) of the strong signals within the channel. That is a disaster, even with the fixed time frame of FTn where no new station is supposed to jump in mid-epoch. |
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Re: QCX + New Build - Display acting up
Hi John. Since it works then fades out, it's likely just a cold solder joint. There are a lot of solder joints between the microcontroller and the display unit... connections to the microcontroller itself, to the angled male pin headers on the main board, to the female pin headers on the front panel board and both ends of the little wire cutoffs used to connect the display to the display board. Make sure they all are good, especially the ground connections on the male pin headers since these large pins take some pretty good heat to get a good solder flow to the ground pads on the main board. It's rare but not unheard of to find an?open trace on the circuit board as well,?but that's the least likely scenario. Follow the schematic and use your ohm meter to verify end-to-end continuity from the appropriate pins of the microcontroller to the associated pins on the front of the display board (with the display board plugged into the main board and the unit powered?off).? 73 ... Ron On Thu, Oct 26, 2023 at 2:21?PM John Schreiner <jskcs1@...> wrote: Hello, just finished up my 2nd QRP Labs kit, this time I took on a 40M QCX + and just powered it up in the last hour. |
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Re: QCX-Mini no RF power
You're?doing great Daniel. So the indication is that you have an open?circuit somewhere between Q6 and Q1,2,3. Use your ohm meter to find it. The circuit trace between L4 and Q6 collector is a very short wide trace on the bottom of the board. The trace from L4 to the Drain of Q1 is on the top of the board, coming out from the center of L4. If the solder connections on both ends of both of the two traces are good, find which trace is open and replace it with a short wire jumper. The?drain of Q1 connects to the drains of the other two BS-170s via wide traces on the bottom of the board. These traces are probably OK since you are seeing the same issue on the drains of all three BS-170s.? Good luck .. 73 ... Ron On Thu, Oct 26, 2023 at 2:30?PM Daniel Servian <daniserdel95@...> wrote: Hi Ron, Thank you for helping me. I measured your suggestions: |
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QCX + New Build - Display acting up
Hello, just finished up my 2nd QRP Labs kit, this time I took on a 40M QCX + and just powered it up in the last hour.
The display was working, I adjusted the back pot to see it and then I appropriately set the rig for the wrong band LOL!! Anyway, the display lettering goes dead, its still backlit and powered but no text anymore. I tried adjusting the pot but no luck. I turned off the rig and read the manual on how to reset it to begin again and put in correct band. The display worked a 2nd time and while I was dialing up to a menu the text display went out and was just lit up, no text. I tried reflowing some solder on the pot and such, but now it wont work at all. I power it up, it lights up but there is no adjustment range now in that pot to? get the contrast right to show text.. Any thoughts appreciated. At least it did not smoke up like my first kit build!! 72 John-N2LK |
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QCX + New Build - Display acting up
Hello, just finished up my 2nd QRP Labs kit, this time I took on a 40M QCX + and just powered it up in the last hour.
The display was working, I adjusted the back pot to see it and then I appropriately set the rig for the wrong band LOL!! Anyway, the display lettering goes dead, its still backlit and powered but no text anymore. I tried adjusting the pot but no luck. I turned off the rig and read the manual on how to reset it to begin again and put in correct band. The display worked a 2nd time and while I was dialing up to a menu the text display went out and was just lit up, no text. I tried reflowing some solder on the pot and such, but now it wont work at all. I power it up, it lights up but there is no adjustment range now in that pot to? get the contrast right to show text.. Any thoughts appreciated. At least it did not smoke up like my first kit build!! 72 John-N2LK |
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QCX + New Build - Display acting up
Hello, just finished up my 2nd QRP Labs kit, this time I took on a 40M QCX + and just powered it up in the last hour.
The display was working, I adjusted the back pot to see it and then I appropriately set the rig for the wrong band LOL!! Anyway, the display lettering goes dead, its still backlit and powered but no text anymore. I tried adjusting the pot but no luck. I turned off the rig and read the manual on how to reset it to begin again and put in correct band. The display worked a 2nd time and while I was dialing up to a menu the text display went out and was just lit up, no text. I tried reflowing some solder on the pot and such, but now it wont work at all. I power it up, it lights up but there is no adjustment range now in that pot to? get the contrast right to show text.. Any thoughts appreciated. At least it did not smoke up like my first kit build!! 72 John-N2LK |
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Re: QCX-Mini no RF power
Daniel, please measure the resistance?from the drains of Q1-3 to ground. Should be a high value. It it's very low then you might have one or more?shorted BS-170s. If?it's a high resistance value, then measure the voltage between the Q6 collector (not drain... it's a BJT) and the drains of Q1-3?while transmitting. This should be a very low, almost zero voltage indicating no voltage drop across L4. A voltage drop there indicates an open circuit in the DC path. Something in the area of L4 is suspect since you have close to 12v on the collector of Q6 and close to zero volts on the drains of Q1-3. With the radio powered off, you can also check for continuity between the collector of Q6 and the drains of Q1-3.? 73 ... Ron On Thu, Oct 26, 2023 at 1:33?PM Daniel Servian <daniserdel95@...> wrote: Hi, thank you for your response. |
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#qmx #troubleshooting New QMX troubleshooting advice?
#qmx
#troubleshooting
Hello all,
I finished building my QMX yesterday and powered it up today with partial success - the terminal interface works (sort of) but that's about it. Here are some notes on my observations: ¡¤??????? Powered it up at about 8 VDC. No current draw. Pressed the left encoder and current went to 170 mA. No backlight and no text on the LCD. ¡¤??????? Plugged the USB in to my PC. I saw the simulated flash drive. Downloaded the firmware and dragged it to the flash drive. ¡¤??????? Apparently it did install because I found drive COM3 and when I connected using PutTY and pressed Enter, a diagnostic screen came up. The LCD is still blank. ¡¤??????? Some things don¡¯t look right in the diagnostics screen. The 3V3 SMPS shows ¡°linear¡± and 2.55 VDC. The 5V SMPS shows 5.69 VDC, 62% duty cycle. Supply voltage is shown as 8.6 VDC but it¡¯s actually 7.50 V or internally, it¡¯s 7.4 V. ¡¤??????? I pressed the encoder buttons and tactile buttons and rotated the encoders and all gave the expected response on the screen. ¡¤??????? The manual talks about going to various menus in the terminal mode, but I¡¯m not able to leave the diagnostics screen. ¡¤??????? I plugged in some phones and hear no sound ¨C no hiss, hum or anything. ¡¤??????? I don¡¯t know what the expected voltages would be, but I checked the accessible (top) pins of the SMPS supplies, L to R with the pins facing me:? 5 V unit: 7.40 V, 1.77 V, 7.47 V, 2.88 V and 3V3 unit: 0 V, 2.88V, 7.45 V. ¡¤??????? On the troubleshooting page, I see that the LCD contrast control should be fully CCW, so I disassembled the unit to get at the pot and set it there. Now I get a series of dark blocks on the top line and nothing on the bottom line. I was able to make more contrast adjustments, but no text appeared. The rectangles get lighter and finally disappear. ¡¤??????? I looked for some pins where supply voltage should appear. I found a couple of Vcc pins that read 5.00 VDC. The supply pin (pin 1) for the Si5351 reads 2.83 VDC. ¡¤??????? Checking the LCD pins on top of the display board, I show most are close to 0 V, while Vo (contrast) is around 0.68 V depending on where I set the contrast. Backlight ¡®A¡¯ is 5.00 V and ¡®K¡¯ is 2.7 V. ¡¤??????? I think the 3V3 supply may not be starting and the reference voltage may be wrong. But I don¡¯t know enough to pursue those ideas. |
John Schreiner
Ryuji Suzuki AB1WX
Ronald Taylor
Nick Kennedy