ATS-3A keying thump revisited
- I made a serendipitous discovery today. I noticed the processor
wasn't resetting normally in K2OQ's newly completed ATS-3A, so I
pulled out the board to fix an unsoldered pad on the twisted U12
reset chip. I also swapped out the 22uF cap for a 100uF. At the same
time, I noticed that L3 had been wound with 14 turns instead of 13,
so I corrected that as well. When I was done, I found that the key-
release thump was much more pronounced; a real thump instead of just
a click. Tacking the 22uF cap back in on top of the regulator chip,
in parallel with the 100uF changed nothing. The thump is now as
heavy as it was on my ATS-3A before doing the Mute-line resistor and
I figure that the reset-chip fix is totally unrelated, so my
conclusion is that changing the number of turns on L3 made the
difference. I don't know what to make of that, though. I know I'm
counting the turns correctly (1 pass through the center = 1 turn); my
counts on the band-module coils match the pictures in the manual.
Any thoughts? Aside form the thump, what's the effect of using 14
turns on L3 instead of 13 turns (increasing the inductance by 16%)?
Measured power output is the same with either 13 or 14 turns.
- Never mind. I tried reversing the changes I had made (except for that
which fixed the reset circuit) and the click/thump remains about the
same. In this case, the 100uF cap doesn't seem to do any better than
the 22uF either. It appears that this ATS-3A will need the resistor
and cap on the Mute line, as did mine.