Bob, I would think Q3 is OK since it simply acts as a switch - it does not produce any voltage. The MCU (U1) pin 39 is the source for voltage on the drain of Q3, and a high level of somewhere near 5 volts is to be expected.
Look somewhere else for the problem. It is difficult to see directly whether the microprocessor is creating the correct output because it is fed to the relay drivers as serial data, but the relay driver pins should have the outputs for the selected relays at a low level, and go to about 12 volts on the pins connected to the unselected relays. Check the schematic sheet 1 to see which pins correspond to which relays. 73, Don W3FPR > -----Original Message----- > > In troubleshooting a relay problem on my KAT100, Gary advised me > to check the > signal /8R, generated by Q3. I think Q3 may be faulty, since > (using a Fluke > DMM) signal /8R alternates between zero and only 4.99v as the KPA100 is > cycled between receive and TUNE. Signal 8R alternates between > 7.91v and zero, as > I would expect. > > Before, I disassemble, de-solder, and install a new Q3, however, could > someone verify that 4.99 v is indeed lower than it should be and > Q3 is probably bad. > Thanks. > > -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.338 / Virus Database: 267.9.4/57 - Release Date: 7/22/2005 _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
