[Elecraft] Interesting KPA100 partial power control loss
Ted Turk
tedg7bqm at fastnet.co.uk
Sat Jan 23 16:55:19 EST 2010
Good evening all,
K2/100 #5822 started yesterday producing nearly double the requested
power. Below 10W fine. 50W requested gave about 100W and max power
was approaching 160W on lower bands!! I searched the reflector
archive to confirm my memory of posts on the problem over the years.
As suggested by Don W3FPR in the past, I replaced D16-17 with 1N4148
diodes to see what happened before delving further, fearing damage to
U5 or U6. On reassembly the problem was fixed!
I checked the removed 1N5711's with a Peak DCA55 and both appeared
normal (low voltage test only I suppose).
Have been playing with a kit built Linear Amp Ranger (572B) recently
(circuit similar to Ameritron AL-811HD) and I am suspicious that on
powering down the heavy toroidal mains transformer may be producing a
small 'EMP' since occasionally it freezes up a nearly G4 iMac. The
antenna is either disconnected or switched to a dummy load when off-
air. No recent thunderstorm activity here - midwinter.
Does anyone have any ideas on how to reduce this turn-off spike, in
case this is the cause? All gear is fed from UK 240V mains via surge
protected power outlets. Meanwhile I will be even more vigilant with
antenna disconnection and grounding.
73,
Ted G7BQM
More information about the Elecraft
mailing list