MOTM

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

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
> 
> 
> 
>

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
> > 
> > 
> > 
> >
>

Hopefully Paul will add Mouser part numbers to the BOMs someday. I've  
gotten some bad parts myself.

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
> > >
> > >
> > >
> > >
> >
>

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

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@yahoo.ca 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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Hi,

  I double checked all the component values and also had a friend of
mine who specializes in synth repair look at it and all the components
are correct.  I'm using alpha pots so maybe the +-%tolerance of the
alpha pot takes the filter sweep out of range at the top end?  I don't
really know... I would think it would take more than that.  Any other
guesses as to the problem?

Thanks,
Dave


--- 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
> 
> 
> 
> 
> 
> **************Play online games for FREE at Games.com! All of your
favorites, 
> no registration required and great graphics â€" check it out! 
>
(http://pr.atwola.com/promoclk/100000075x1211202682x1200689022/aol?redir=
> http://www.games.com?ncid=emlcntusgame00000001)
>