开云体育

Hello, all.? You may have seen me jump in with some photos with a burning Q7 saga.? Well, I bypassed Q7 after it burned a hole in my board for unknown reasons and made a few contacts on JS8 (never checked output power.)

Today I was finishing up my multi-banding of the 50W amplifier to work with the QDX and was testing the outputs of the X6 band select pins.? Pins 0 and 1 were giving me a positive indication when moving from 80m to 40m but pin 2 never went high for 20m.?

In troubleshooting I did the following:
1. I checked IC2 for voltage and it was putting out 5.03v.?
2. IC1 is putting out 3.3 volts.?
3. So I checked the pad at Q5 to see if it was getting voltage; it was not.?
4. I removed Q5 and checked for voltage; still none.
5. I checked continuity to ground... pad on Q5 and X6 pin2 were both grounded.?
6. I traced every pad, via, and trace and could not find a short along the 20m LPF signal line.? I scraped the edges of the pads, added flux, and reflowed the solder that was there to make sure it wasn't contacting the ground plane; still shorted.
7. I cut the trace between Q5 and X6 pin 2; short existed at X6 but not at Q5.
8. I cut the trace between X6 pin2 to and the uC (IC8); X6 no longer shorted but the pin on the microcontroller still is.??

So... how could I have an internal short in the microcontroller for the 20m LPF?? Something is awry.

Joshua
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For comparison, I just checked my other QDX (also V3 and also wired for 12v.)??

IC2 is running at 57C where the dead QDX is 78C.
All X6 pins show 3.3v at correct times and 0v when not activated. (dead QDX shows .8v on pin 0 when not activated.)

Joshua

Well, I figured it out...? ?

I was pulling power off the 12v connector on the top of the board.? The only place to get a ground off the DC jack is on the side but it turns out that is not a real negative lead, it is open once you plug something into the DC jack.? So, my buck converter powering my nano was getting a ground backward, through the band pads, through the uC on the QDX, and through the Nano I was using for band switching my LPF kit.? I just killed my other (good) QDX.??

I figured it out by disconnecting my band wires from X6 and plugging in my LPF switching circuit alone.? It did not power up.? So I touched a band wire to a X6 pad and the circuit was powered.? I guess I'm putting in another order with Hans.

P.S.? I just noticed I called the microcontroller on the QDX an Atmel and it isn't; it's an STM.
Joshua

After sleeping on it, there are two solutions to keep this from happening in the future.

1. Use a high impedance resistor between the QDX and the Arduino Nano to keep it from ever sinking enough current to cook the STM pins (and use a proper ground like the USB connector shell.)

2. Forget the microcontroller and buffer the QDX band signals with some transistors (I'll probably do this).? The microcontroller is easy to change configurations on with software where as the transistors would require a soldering iron to change things up.? But... the microcontroller is also subject to crashing due to RFI and it would be nice to take that out of the equation.??

I have two more QDX on order now so I'll get to test in the coming week or two.? I am happy to receive the V4 board since I still got occasional popping on the V3 even after the firmware updates and HF packet really doesn't do well with the deviations in frequency.

Joshua

I must be in a building funk!? I built my 20m QCX-Mini, finishing up last night.? I performed an alignment and listened to some signals.? Then I added the AGC board and set to a level I liked before continuing on to frequency adjustment.? While moving through the menus, my tactile buttons stopped doing what I wanted.? Now I have high current draw, a hot 5v regulator, 22ohms across the 5v rail, and a non-functioning right button.? I removed the 328P and all is fine.? I must have murdered another microcontroller and created an internal short.??

My first thoughts were faulty solder joints, AGC module causing a ruckus, a cutoff shorting something, or ESD.? I removed the AGC, inspected the board very closely, and I work on wood.? I have no carpet, don't sit on a fabric chair, and the table is wood so ESD is possible but less likely than an average home.

I learned my lesson with the QDX mishap... I'm not taking my 328P from my 40m QCX to try on this board...? I am going through the process of burning fuses and uploading the firmware to a 328P I have on hand.??

Hopefully no more smoke!

Joshua

QCX is back up and running.? Built another QDX and it is functional.? I assembled a BPF buffer board and managed to keep all the magic smoke in all the components.? They say it comes in threes.? Hopefully I got all three out of the way.

Joshua.