Bill ... 13.8VDC would be the absolute max for the main boards ( BITX40 and uBITX). I would suspect this level is stressing the raduino, relay coils etc. over time, and stuffing the gear in an enclosure would raise the internal temp very quickly as well.
FUSE your PA and BOARD appropriately! I use a 12v sealed battery portable or a switch mode wall wart repurposed for the BITX. Output is 12.1 VDC at 2.5 Amps. There is no stress on my motherboard and in the unfortunate event of a IRF510 current runaway (high swr) or failure, the most current drawn will be limited to a couple of amps. My main shack supply would supply 30 amps plus and a lot more smoke. I have run the BITX40 for over a year now making over a hundred contacts across 3 continents with no problems, often having the rig on for the whole day. Using original heatsink on the PA but I did put another sink on the 5V regulator for the raduino just in case. Went through a few wall warts before I found a "quiet" one. Stable clean DC power is paramount.?
I plan on using same power for the new uBITX but will do the 5V reg mod on my TDA2822M chip just in case. I use a built in small speakers and/or external DSP audio filter/amp/spkr - no headphones. Will be mounting? the PA's to a metal backpanel with mica insulators on this build and a sink on the raduino 5V regulator? too.
73 Tom VE3THR
