> Seems a little less-likely to be the problem, given(?) as well that you have > fairly consistent (is deterministic overstating it?) behaviour.
Yeah. We've gotten to the point now where enough layered problems have been cleared away that the remaining behavior is quite deterministic. > If you wanted to test it by experiment, without having to remove the > installed Rs, you could test-clip another R in parallel with the 38.4K, > probably something around 200K, to shorten the 555 period. Yes; and I think a quick solder tack for that would even be easier to manage than clips in there. Will give that a go this weekend. cheers, --FritzM.