In a message dated 2/7/02 9:49:12 PM,
motm@yahoogroups.com writes:
<< "corelli44" <
john@...> wrote:
Hello List,
I have an old Volume/Modulation pedal that I got with my original DX7
back in 1985. I'm trying to measure the resistance to see how to use
it with the pedal interface but I'm not getting very clear numbers.
I get readings between 25 and 40 most of the time with the pedal up
or down. It does go up to as high as 150 sometimes but very briefly
(could this be my DVM? It's quite cheap).
Also, I only get readings with leads on the very tip and behind the
first ring on the plug. I get nothing with one of the leads between
the two rings (and the other on either side of either ring). Is this
the way the newer Yamaha pedals are wired?
I'm just wondering if older pedals might have been made a bit
differently than the newer Yamaha pedals or if they should be
somewhat similar (if anyone has any experience with older pedals).
>>
The foot pedal you have is a model FC4. The pedal they are currently making
is the FC-7. The old FC-4 is an opto-electric pedal. It contains a small
incandescent light bulb and a photoresistor. Two of the TRS plug conductors
are connected to the photoresistor; the other conductor supplies DC voltage
to the light bulb. Movement of the pedal opens and closes a small shutter
between the bulb and the sensor, allowing in or shutting out the light from
the bulb. With no power applied to the lightbulb, moving the pedal (opening
and closing the window) won't really change the measured value of the
photoresistor (it's dark in there!). This is in contrast with the newer
"passive" FC-7 pedals, which are potentiometer-based, so their resistance can
be varied with no power connected.
For more reasons than one, it's probably a better idea for you to try to
obtain one of the newer pedals for use with your analog equipment.
Michael Bacich