vco7c thermal results

[jorgen.bergfors at idg.se]

>I did a few experiments for the fun of it. I set the vco at 440hz then
>sprayed freeze on the 3046 for 1 sec. freq went up to 582hz . It took it
>about 60secs to recover to 440hz then after a little minor drifting
>stabilizing at 440hz in about 3mins. Then I took my 45w iron and placed it
>in the middle of the 3046 for 30secs. The freq went down to 382hz again it
>took it about 60secs to recover to 440hz stabilizing in about 3mins. So I
>got out the hair dryer full bore and max heat about 6" from the board for
>30secs freq went down to 332hz and took about 5mins to fully recover.
 >-tg

This might indicate that the temperature compensation does not work, but on the other hand these tests are rather extreme. You should perform some tests that more resemble normal use. Around ten degrees change inside the synth is probably realistic when you do a live gig. This corresponds to a larger change in free air, as the synth case isolates  more than you would expect. For studio use the temperature variation ought to  be less.
Below is an example how you can do a real world temperature test:

I put the VCO board (size 50 x 75 mm, 2 x 3") in a shoe box and put on the lid. 20 cm (8") from the box I placed a 300 watt infrared heater. After 15 minutes the temperature inside the box had rised from 24 to 34 degrees C. This was less than expected, as the box was just bearable to touch on the outside (the side facing the heater).
With the tempco the frequency of the VCO increased from 518 to 523 Hz. This corresponds to 17 cents or 1/6 of a semitone. With the tempco replaced by a normal 1% metal film resistor, the frequency increased from 424 to 470 Hz. That's 190 cents or almost two semitones.

/Jorgen