[sdiy] ARP VCO drift - update

[Tom Farrand]

I didn't know about that part ... thanks!

Nice little part in a DIY package.  I wonder if that part could
tolerate a Panasonic SMT tempco nestled underneath the SC-88 package
by "stretching" the BC847 leads.  Maybe a little shot of thermal
grease and then overmolded with an epoxy cap.  Hell, even better to
use one of those SMT to DIP adapter boards and bodge that up with the
thermal grease and epoxy.  Then plug it into a socket like any IC
component.

Hmmm.  Lots of possibilities there.

Tom Farrand


On Sun, Aug 17, 2008 at 3:26 PM, rob <rob at emulatorarchive.com> wrote:
> Hi list,
> Quick update on progress.....I fitted a BC847BPN dual NPN/PNP transistor to
> the Tempco using heat paste and wrapped the 2 together using insulation
> tape, even though this is remote from the main PCB. The BC847 was fun to
> wire up....its super glued to a tiny piece of veroboard with thin wires to
> the SMD transistor and larger wires to the PCB.
>
> VCO frequency drift has now reduced to a similar level as a Dual
> SSM2210/Tempco based VCO (Oakley or E-mu Systems). I test with a frequency
> counter, but the real test is to listen to the 2 VCO's at the same pitch and
> hear the tones beating. They are now nicely beating against each other with
> a 5 - 10 second phase rather than quickly going away in pitch.
>
> The transistors and tempco will now be put on the main PCB and I'll carry
> out the next set of tests. 1v/octave Tracking....maybe I'll pot the whole
> circuit....
>
> Thanks - Rob
> www.emulatorarchive.com
>
>
>
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