@Roger, thanks for the heads up... I solved the problem yesterday as per
Yesterday, after I posted the question to the group, I went back to the
schematics, resolute to find some additional component or connection to
that node of the input of the A/D processor.
It happened that the answer was right there on Diagram <1>, the low pass
filter comprised of C3023 (22n), C3024 (33n), R3023 (2M2) and U3023D (1/4
This low pass filter is engaged in all functions and in all ranges, EXCEPT
in OHMS *and* 20Meg range (which perfectly explains why, only when I set
that mode, I could see the right voltage).
I was blind to that part of the diagram because, in recollection to when I
got the scope, when the function TIME and 1/TIME was non functional
whatsoever, and when I first studied the schematics of the DM44, soon
enough I learned that this low-pass filter didn't have an *active* role in
any of the DM44's functions and simply started ignoring it from that point
Yesterday, when I systematically started searching for something else that
could still be connected to that node (that could explain the leak), I
finally paid attention back to this circuit and realized that it could be
Upon returning home, I just lifted, one at a time, C3023 and C3024... and
Voilà! C3024 (33n, PoliStyrene cap, 200V) was the one causing the droop.
I didn't have a PoliStyrene replacement, but did have a PP of exactly the
After replacing C3024 and confirming that the meter was stable again for
more than an hour (which never happened), I was able to remove the LF411
buffer from the A/D processor input, and it remained working fine and was
relieved to know that the LD111 was not faulty.
I think that - FINALLY - I got this 464 + DM44 FULLY FUNCTIONAL.
I will work now on documenting the main chapters of this story and posting
it to the Files / Pictures area (will take some time to put together).
2017-07-04 7:25 GMT-03:00 very_fuzzy_logic@... [TekScopes] <
[Non-text portions of this message have been removed]