[sdiy] Do Tempcos go bad?

[Ove Ridé]

The tempcos are integral parts of the circuit. If any of them went open
circuit, the oscillator simply wouldn't work correctly at all. Depending on
which one failed, you might see no oscillation, or a super low or super
high frequency.

On Thursday, 27 October 2016, Andrew Simper <andy at cytomic.com> wrote:

> Would the oscillators drift if they differed in temperature from each
> other with the tempco broken so it was an open circuit?
>
> On 27 October 2016 at 09:09, Paul Perry <pfperry at melbpc.org.au
> <javascript:;>> wrote:
> > I think the earliest tempcos were a coiled length of very fine copper
> wire,
> > so if they did fail, I expect the likeliest thing would be to go open
> > circuit,
> > which would be obvious. I don't think they would simply drift in value.
> >
> > paul perry Melbourne Australia
> >
> > ----- Original Message -----
> > From: Nicholas Keller
> > To: synth-diy
> > Sent: Thursday, October 27, 2016 3:31 AM
> > Subject: [sdiy] Do Tempcos go bad?
> >
> > Strange question, probably, and I imagine all parts can age and fail, but
> > are tempcos generally formidable?
> >
> > The reason I ask: as an SRM owner, a friend in another state asked me to
> > help troubleshoot his Cat SRM which is behaving in such a way that each
> VCO
> > is drifting independently (I apologize for the remote third-party help
> > request).  He's had the PSU looked at about a year ago or so and was told
> > that it was stable and that the keyboard CV is also reliable.
> >
> > I had heard that the Cats used poor quality trimmers and that often these
> > were the cause of jumpy and unstable pitch. However, a tech in his area
> > who's services he cannot afford has suggested that the tempcos are
> probably
> > the culprits.  Can anyone throw in some opinion or experience so I can
> pass
> > on some advice to him?  Swapping out tempcos is something he can probably
> > handle himself, although I've warned him that post-repair calibration
> could
> > be tricky without good test equipment. Thanks for any suggestions.
> >
> >  Below are links to some pics showing the location of the tempcos "as
> shown"
> > in the schematics and "as installed" on the VCO board, one is across the
> > AD821 and two (both labeled R150) are across the CA3046.  Keep in mind
> that
> > the schematics for the SRM do not always match the layout diagram, and
> > neither of those match the actual PCB :(  I suspect the "extra" R150 is
> > actually across the AD821 and that the "real" R150 and R83 are across the
> > 3046.
> >
> > https://imgur.com/a/3sRfG
> > https://imgur.com/a/9Wsl9
> >
> > Thanks
> >
> > Nick
> >
> > ________________________________
> >
> > _______________________________________________
> > Synth-diy mailing list
> > Synth-diy at dropmix.xs4all.nl <javascript:;>
> > http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
> >
> >
> > _______________________________________________
> > Synth-diy mailing list
> > Synth-diy at dropmix.xs4all.nl <javascript:;>
> > http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
> >
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at dropmix.xs4all.nl <javascript:;>
> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>


-- 
/Ove

Blog: <http://blog.gg8.se/>

"Here is Evergreen City. Evergreen is the color of green forever."
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://synth-diy.org/pipermail/synth-diy/attachments/20161027/d7351254/attachment.htm>