There have been a lot of discussions about protecting the BS170 power amplifier transistors from our bad SWR mistakes.? Zeners and TVS diodes get a lot of consideration.
BS170s cost about $.40 each and are very easy to replace.
The microprocessor is not easy to replace.? Fry it and you're back to Square One winding toroids for a new kit.? And probably grumbling even if you're a nice person.
So would overvoltage protection here be a good idea?? Even just on a temporary basis on a newly built board?? Maybe a nice burly 3V3 zener rated for 3 amps, to clamp VDD, at least until you know the transceiver works properly.? Here's an OnSemi part: 1N5913BRLG, under 50 cents at Mouser, qty 1.? It can dissipate 3 watts continuous.? It probably won't be happy at that, but you'll use your on-board test equipment (your educated finger) to see if it's happy.
Yes, I do see D109 on the 3V3 power supply board.? It's a 3.6 V zener but max dissipation is 1/2 watt.? I want a burly diode on my side during initial testing.? If your temporary zener even gets warm, you know there's a problem, but the MPU lives on to fight another day.
Look, I'm not a EE.? I can fix your brakes.? Is this a dumb idea?? Sanity check me, please.
