Greetings all,
I have read posts related to T1 in the QDX getting hot as well as various other specific components getting hot, but what could cause the entire PCB (or close to it) to get hot? As in, 'want to drop it right now' hot, despite the fact that you're holding the PCB by the edges? Since the heat also appears on the shell of the USB connector and the outer part of the BNC connector, factoring in that Hans states that most any surface area of the PCB not otherwise in use is used as a ground plane, my guess is that something(s) is/are generating that heat and dumping it to the ground plane.
For those keeping up, I was able to successfully jumper from T1 over to the drain of Q11 (see below). The jumper is just a piece of insulated 22ga solid wire with the bare ends bent into hooks. The heat issue began before I put the jumper into place. As for Vcc, with 11.98V coming in, 11.87V reaches the center tap of T1. Checking the drains for Q8 and Q10, I get 11.87V. The drains for Q9 and Q11 also meter 11.87V. The gates on Q8 and Q10 meter ~2.4V. The gates on Q9 and Q11, however, read ~51 mV. One note I should make is that when I was troubleshooting the Vcc supply issue, while I did not have it connected to a computer, neither did I have even a 50-Ohm terminator on the antenna port (*embarrassed look*). I completely forgot about it. I don't know if the voltages on the gates for Q9 and Q11 mean that I've fried the MOSFETs by accident due to that OR the lack of an antenna or dummy load is causing something to heat up the PCB.
While I plan on checking the QDX temperature again with a dummy load attached and also see how (if?) things change when I use a buck converter to lower the supply voltage (it was built for 12V), what else should I look for when I get back to the bench? Are there any particular components I should check?
I appreciate the help!
Charles Johnson
KF4AYT
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