[sdiy] uA726 temp setting

[Grant Richter]

Hi Kevin,

May I suggest looking at the setup procedure for the Moog Source
oscillators?

Those are based on a thermostated CA4046. The procedure is given for setting
the internal temperature to 130 degF, by measuring the millivolt drop at the
expo transistor base-emitter junction. The BE drop increases by 2.2
millivolts per degree, so you can measure the internal temperature by
measuring the BE voltage. The formula is given in the Source service manual.

Reliability of solid state devices is directly related to temperature. Using
a lower temperature will extend the uA726 lifetime.

> 
> So, does anyone have any idea what this should be set to?
> I don't care how it's expressed: resistance, voltage or current.
> One would guess the setting to be somewhere 150K or over, or they
> would have installed a 100K trimmer (or expect 726 tolerances to be
> very different from each other.)
> 
> Any clues would be nice.
> Getting a Sonic Six to track well is hard enough when the temp IS set
> correctly, but it's almost impossible if it's off.
>