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[To reduce potential confusion, I've deleted my original response (that Hans subsequently pointed out was in error)?to Razvan's question (post #117718) and reposted the response here corrected.]

For the Rev 1 PCB?there are a few?optional?modifications that could be done, none are necessarily recommended.

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I've replaced the stock Zener diode on the 5V smps board with a 5W version as a precaution. Not easy as one has to remove the original, then add a couple insulated leads to the pads since the 5W Zener will need to ride above that spot in order to fit. I'd recommend just purchasing a set of replacement SMPS boards from QRP-Labs as the path of least resistance (not measured in Ohms).

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If you need USB-C to USB-C connectivity to a PC, there are 2 smd resistors that will make that type of connection work more reliably. Again these are tiny components needing careful very fine tip soldering to the USB connector pads, which are very closely spaced. If you instead just use a USB-C to a USB A cable (very common), things will work fine. I recommend this one, as it effectively isolates RF from getting into ones PC (likely more common an issue with end-fed antennas):?

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If you?need?the functionality of the PTT Out jack to be "grounded" (ex: to trigger an SDR switch if using an external SDR as a panadapter), then a jumper wire needs to be installed across two points on the opposite side of the board from that jack. The 5V PTT Out works fine without this mod. (This particular mod applies to Rev 1, 2, & 3 QMX main boards).

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The only other mod I've made is removing the power coaxial jack, and replacing that with about 6 inches (15 CM) of good grade silicon insulated wires terminated with power pole connections. This helps avoid a power disruption if the QMX is jostled while operating. An intermittent power disruption could cause, in some rare cases, the older 5V SMPS board to be damaged.

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So that's the list. Again, these are not necessarily "recommended", as they are entirely optional.