Re: KX1 MAZX supply voltage

Posted by N6KB on Mar 12, 2011; 8:52pm
URL: http://elecraft.85.s1.nabble.com/KX1-MAZX-supply-voltage-tp6095842p6165025.html

Adhering to the instruction manual stated limits is good advice.

On the other hand, check out the schematic and see what parts the supply voltage feeds directly. Only the TX driver and PA, and voltage sense input to MCU chip. The rest is fed by 78L05 and 77L06 regulators. 77L06 data sheet says max input voltage is 16.74 volts. I would certainly not exceed that voltage.

Aside from frying that regulator, the other possibility with too high voltage may be oscillation or thermal runaway in the driver and/or PA transistors. Maybe that could happen below the max input voltage of the 77L06, but I sort of doubt it. The driver and PA transistors are not exotic parts or SMD, so it would not be real hard to replace them if you did smoke 'em.

I have been running mine on 14.9 VDC (according to the onboard "bAt" reading), not because I want to push it to the limit, but rather because the HT charger power supply I found, that conveniently plugs right into the KX1, happens to deliver that voltage. I get about 6 watts out, and haven't smoked any parts yet.

DE N6KB