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
> >
> >
> > ------------------------------------
> >
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> >
> >
> >
> >
>