MOTM

--- In motm@yahoogroups.com, "Paul Schreiber" <synth1@...> wrote:
>
> The caps were melted due to soldering, not of the circuit.
>
> I use the ones from Mouser.
>
> Paul S.
>
> ----- Original Message -----
> From: "lexvortex" <lexvortex@...>
> To: <motm@yahoogroups.com>
> Sent: Tuesday, August 26, 2008 3:53 PM
> Subject: [motm] MOTM 440 problem
>
>
> > Hi everybody, I just finished building a MOTM 440 filter but am having
> > some problems with it. I bought some polystyrene caps from a surplus
> > place that didn't have any voltage rating on them like pauls does on
> > his polystyrene caps (I also have a MOTM 440 built by him, loved it so
> > much I needed another!). After powering it up and trying to use it
> > there was no sound only what sounded like a quiet bleed through of the
> > oscillator hooked up to it which the none of the controls had any
> > effect on. I took it back to the bench and started trouble shooting
> > and what I found was that some of the polystyrene caps were melted, I
> > assume because they had too low a voltage rating (they are smaller
> > than Pauls).
> >
> > What I want to know is if this could have damaged any of the ICs? I'm
> > gonna see if I can find some more polystyrene caps with a higher
> > voltage rating but I'd be surprised if the place has them :(
> >
> > Thanks a lot for any help :)
> >
> > Dave
> >
> >
> > ------------------------------------
> >
> > Yahoo! Groups Links
> >
> >
> >
> >
>

On Sep 16, 2008, at 7:59 PM, Dave wrote:

> As an update to others who may run in to the same problem I had with
> my MOTM 440 build I'll post the solution to my problem. I took my
> MOTM 440 to a tech friend of mine who literally spent hours trying to
> figure what went wrong as at first glance everything was done right.
> After comparing the schemes to the PCB he noticed that the BC550
> transistors were a different configuration (EBC) than what he is
> normally used to seeing (CBE) which I think is fine for most TO-92
> BC550 transistors but not good for the BC550 trans that I got from
> Futurelec which are (CBE). I had all the trans in backwards even
> though I put them in to match the silk screen (I of course didn't
> think to question the orientation of the trans). I'm not sure why my
> BC550s were opposite of Pauls but I did learn a lot about transistors
> as a result of this problem which has actually helped me trouble shoot
> other modules I have built :)
>
> I hope this helps others if they build this and can't figure out
> what went wrong :)
>
> Dave
>
> --- In motm@yahoogroups.com, "Paul Schreiber" <synth1@...> wrote:
> >
> > The caps were melted due to soldering, not of the circuit.
> >
> > I use the ones from Mouser.
> >
> > Paul S.
> >
> > ----- Original Message -----
> > From: "lexvortex" <lexvortex@...>
> > To: <motm@yahoogroups.com>
> > Sent: Tuesday, August 26, 2008 3:53 PM
> > Subject: [motm] MOTM 440 problem
> >
> >
> > > Hi everybody, I just finished building a MOTM 440 filter but am
> having
> > > some problems with it. I bought some polystyrene caps from a
> surplus
> > > place that didn't have any voltage rating on them like pauls
> does on
> > > his polystyrene caps (I also have a MOTM 440 built by him, loved
> it so
> > > much I needed another!). After powering it up and trying to use it
> > > there was no sound only what sounded like a quiet bleed through
> of the
> > > oscillator hooked up to it which the none of the controls had any
> > > effect on. I took it back to the bench and started trouble
> shooting
> > > and what I found was that some of the polystyrene caps were
> melted, I
> > > assume because they had too low a voltage rating (they are smaller
> > > than Pauls).
> > >
> > > What I want to know is if this could have damaged any of the
> ICs? I'm
> > > gonna see if I can find some more polystyrene caps with a higher
> > > voltage rating but I'd be surprised if the place has them :(
> > >
> > > Thanks a lot for any help :)
> > >
> > > Dave
> > >
> > >
> > > ------------------------------------
> > >
> > > Yahoo! Groups Links
> > >
> > >
> > >
> > >
> >
>

--- In motm@yahoogroups.com, kheck73@... wrote:
>
>
> Paul's obviously the expert here. To me, it sounds like most
everything is
> OK, but it shouldn't be doing what you describe across the frequency
range.
> The first thing I would do is to double check is that the proper
component
> values are where they should be. This includes the potentiometers.
You have the
> benefit of being able to directly compare the one you built to your
> Synthtech-built module. Also be sure all IC's are in the correct
orientation,
> especially all of the SSM chips.
>
> -Karl.
>
> In a message dated 10/23/2008 12:09:35 P.M. Eastern Daylight Time,
> lexvortex@... writes:
>
> HI,
>
> I just finished a MOTM 440 filter and for the most part it seems to
> work fine, but I noticed as I turn the freq knob past 9 with the
> resonance cranked the resonance stops unlike my other MOTM 440 filter
> that Paul built. Also if I have the resonance turned down and have no
> audio going through the filter quite a bit of noise comes out of the
> filter after I turn the freq knob past 9. I also noticed that the 440
> that Paul built has a more even sounding resonance across the audio
> spectrum, for example if I use a sequencer on the 1V/Oct input and
> compare the two my 440 sounds weaker and muddier in the lower freq.
> Is this normal?
>
> Thanks for the help,
> Dave
>
>
>
>
>
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