hi-
i recently acquired an [older] belton btdr-1h and experienced the same strong
lfo modulation discussed here in the newer version. thought i'd share my "fix".
reference to the patent shows [indeed] an lfo
built around a single schmitt-trigger inverter. wishing to turn this off, i cracked
open the brick itself. this was easier than i'd imagined - not nearly full with epoxy
and the plastic parts quite soft. sure enough, the diagram in the patent turns out
to be seemingly identical to the actual object, albeit a smd board. finding the
lfo was pretty quick with a probe, and then some continuity tracing led me to the
resistor that feeds the lfo to the clock as a modulating signal. this turns out to
be r9 [clearly labeled] and i fine point soldering tip got the thing off, stopping
the modulation. it'd be easy to re-enable by replacing the SMD part with a bigger
one and a switch. i can send drawings to those who might be interested and
adventurous enough. no idea how easy this'd be with the newer, smaller bricks,
though they seem to be functionally identical.
-michael johnsen
i recently acquired an [older] belton btdr-1h and experienced the same strong
lfo modulation discussed here in the newer version. thought i'd share my "fix".
reference to the patent shows [indeed] an lfo
built around a single schmitt-trigger inverter. wishing to turn this off, i cracked
open the brick itself. this was easier than i'd imagined - not nearly full with epoxy
and the plastic parts quite soft. sure enough, the diagram in the patent turns out
to be seemingly identical to the actual object, albeit a smd board. finding the
lfo was pretty quick with a probe, and then some continuity tracing led me to the
resistor that feeds the lfo to the clock as a modulating signal. this turns out to
be r9 [clearly labeled] and i fine point soldering tip got the thing off, stopping
the modulation. it'd be easy to re-enable by replacing the SMD part with a bigger
one and a switch. i can send drawings to those who might be interested and
adventurous enough. no idea how easy this'd be with the newer, smaller bricks,
though they seem to be functionally identical.
-michael johnsen