The available space for another jack was too tempting, so I planned out this
modification before initial assembly of my MOTM-101. You have a couple of
options for the clock out signal. It could just be a buffered INTCLK
signal, which would make the 555 clock available as a separate output. But
I chose to bring out the signal originating at pin 7 of U7B, which is the
comparator that generates the clock from the external input (normalled from
the INTCLK). That way the clock out is integrated with the module. It
yields the signal that is currently triggering the S&H, whatever the source.
Of course if you are not using the S&H output, you can still use the clock
out.
I bent pin 5 of U3 (U3B) upwards before soldering in the chip and wired the
pin later to buffer the output of U7B. (You also have U8B as a candidate
for the buffer.) You can select the voltage level of this output. I made
a voltage divider with a 39K resistor between U7B-7 and U3B-5 and a 15K from
U3B-5 to ground. That yielded a signal of approximately +/- 4V (a bit
smaller than I had expected, but I didn't redo it). A 1K resistor connects
U3-7 to the new clock out jack.
This mod requires no trace cutting. If you do this on an assembled
MOTM-101, you can probably cut pin 5 on U7B close to the PCB and carefully
bend up what's left. You'd have to solder two resistors to it, if you chose
my approach.
Richard Brewster
----- Original Message -----
From: "Adam Schabtach" <adam@...>
To: "MOTM listserv" <motm@yahoogroups.com>
Sent: Sunday, November 10, 2002 4:24 PM
Subject: [motm] Adding CLK OUT to MOTM-101?
> Today I was watching the LED on my MOTM-101 Noise/S&H module blink merrily
> away. It crossed my mind that it would be handy if that clock signal could
> be used to drive other things. Sure, you can use an LFO to drive the S&H
and
> other things, but if you could drive everything from the 101's clock,
you'd
> free up an LFO for more interesting tasks. So then I noticed that there's
> even room for another jack in the lower row of the 101's panel, whereupon
my
> interest was sufficiently piqued to pull out the schematic.
>
> It looks like tapping the output of the 555 timer would be easy enough. It
> even looks like there is an unused section of a TL072 wired as a
unity-gain
> buffer which could be used to buffer the 555's output, although you'd have
> to cut a PCB trace to free the grounded input, which is kind of scary.
>
> Has anyone tried this? Any reason why it's not a good idea? I realize that
> the 555-based clock probably isn't as stable as the MOTM oscillator core
> found in the 320 LFO, but in many instances it is probably good enough.
>
> --Adam
>
> --
> Adam Schabtach
> adam@...
> http://www.studionebula.com ∗ ∗ CD now available! ∗ ∗
>
>