Re: First HF radio..incensed a week ago...I think I blew up my uBitXv4.


Evan Hand
 

My first thought is to check the mic and key connections.  I have had similar issues with 3.5mm plugs that being pushed in all the way.  One of my key paddles has that issue, and I must constantly check that it is pushed in all the way.

I would verify the operation of the key input.  That is the line that needs the 4.7kohm resistor.  Check with a voltmeter after connecting a dummy load, or disconnecting the power to the power amp finals (the middle connector, brown wire, on the 3 pin header on the main board).

Did you by chance get one of the AmatuerRadioKits cases?  If so, I would verify the soldering on the front PCB, making sure that all of the 3.5mm jacks are soldered correctly, and no shorts.  You will also need another 3 pin header plug to separate the PA power, as the instructions for that case has you connect them together at the back PCB.

In any case, I think that you have a wiring issue that you need to resolve.  With the situation that you describe, even a short blip on the transmit key can cause the Nano to lock up due to RF feedback when you do not have a matched load.  Before breaking out the scope, I would attach a dummy load and verify that it operates properly. 

A good 20 watt low-cost dummy load can be ordered from QRP-Labs for $8.50 plus shippling.  Alternates can be had from Amazon, though without the power breakout circuit.
https://smile.amazon.com/Mcbazel-Surecom-0014-0153-PL259-1-0GHz/dp/B07MH6WPZL/ref=sr_1_12_sspa?dchild=1&keywords=qp+50+ohm+dummy+load&qid=1601068560&sr=8-12-spons&psc=1&smid=A263LSCPZJCHO0&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUFNVFBaN1dGWk1aNzEmZW5jcnlwdGVkSWQ9QTA0NTU4MjgzVVFLVFNaQjZNWExSJmVuY3J5cHRlZEFkSWQ9QTAzMjY5MjkzSlFaSlpRQUdGU0xNJndpZGdldE5hbWU9c3BfbXRmJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==

Hope this helps.
73
Evan
AC9TU

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