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Had my uBitX v.6 do something strange today. I hooked it up to my laptop via the USB cable, and the display came on as usual. I connected antenna and power, and was ready to go. Only I couldn't get any RF out. I also noticed that when I turned the volume control up, the side tone was distorted, but turning the volume back down it was OK again.

I could hear signals perfectly fine, but I had zero power output. I checked it with several different meters, no joy. I thought I had blown the finals or something.

Eventually I unplugged it from the computer, turned it off and then turned it back on again. Tried transmitting, and I now had full power output again. And everything still worked fine after connecting it to the laptop again.

Has anyone else experienced this before? Or is this just some strange glitch unlikely to ever happen again?


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Tom Sevart N2UHC
St. Paul, KS

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Tom,
This fits the behavior of not having the 12V power supply connected/turned-on.
I've experienced listening to RX while forgetting to turn on the power supply.? (not saying you forgot, just that I have)
USB 5V back feeds through the regulator on the Raduino and powers the uBITX main board.? RX is operational.
I chose to remove the diode on the Nano that allows for the Nano to be powered from USB.
This is one method to leave the USB plugged into the computer and actually shut off the uBITX.

That removed diode now resides in series with R52.? Two birds with one stone.

Rgds,
Gary

Yes, 5v from the Nano can go back through the LM7805 and power the uBitx?
main board from the USB port.? That's asking a lot from the tiny diode
on the Nano.? If you work with the Nano much, it is very handy to be able to
have it powered?from the USB port when programming it.

Could add a diode between the 12v pins of the Raduino and pin 1 of the LM7805.
That way there is no need to repeat the mod if using multiple Nano's,
and the voltage drop across that new diode takes some of the heat off the LM7805.
Protects the Raduino if somebody plugs power into the uBitx with leads reversed
(though reversed power can still damage to the main board).
One of the axial leaded 1n4000 series parts (1n4004 or 1n4007 perhaps) works fine.

Jerry, KE7ER

On Sun, Mar 27, 2022 at 08:25 AM, Jerry Gaffke wrote:

Could add a diode between the 12v pins of the Raduino and pin 1 of the LM7805.

Agree that this is how the Raduino should have been revised.

Yes, the Nano diode mod would have to be repeated per Nano, but you have to get your iron out to build another "an upside down Nano", so not much extra work while you are at it.? I don't reprogram the Nano out of the radio, and I have other ways to supply Vin if the need arises to program stand alone.?

For normal use, I like having the Raduino and Display power controlled by the uBITX power switch. I can leave a normal USB cable connected without them being USB powered.? I also like not having the port available if the radio is powered off.? You would not get these features with the diode mod only on the Raduino.? My simple mod suits me well for now, may not be the best for others.?

The display on the V6 is pretty power hungry when running at 5V, but that's another thread.

Rgds,
Gary?

On 3/27/2022 10:04, Gary Anderson wrote:

I've experienced listening to RX while forgetting to turn on the power supply.? (not saying you forgot, just that I have)
USB 5V back feeds through the regulator on the Raduino and powers the uBITX main board.? RX is operational.

I've never had that happen with mine. When I plug into the USB, it turns the display on, but I don't get any audio until I connect power. Or at least I think that's how it works, usually I plug in the power before I switch it on. Maybe I never noticed that plugging into the USB powers the receiver. I've only had this radio for a few months.

It could have been a bad power connection. The power cord was plugged into the cigarette lighter jack on the power supply and may not have been pushed in all the way.

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Tom Sevart N2UHC
St. Paul, KS

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I leave the USB connected all the time for CAT control - logging and digital modes. I just didn't connect the power lead to the USB connector, so 5V never gets to the Arduino.?

No problem at all programming the Nano with only the UBITX power.

Dean