[sdiy] Jupiter 4 overall tuning drifts after it gets warm

[lanterma at ece.gatech.edu]

On Jan 5, 2011, at 9:56 PM, Gil W. wrote:

> Well the 726 ICs are on each of the four voice boards. Basically I assume the problem is not on any of the voice boards themselves as the total tune changes, not the tune of an individual voice... Also, if I'm not wrong, the 726 are not responsible for the tunning itself but for tone generation in the JP4 ??

They'd be used in the exponential voltage-to-current converter driving the integrator, and hence a very very very important factor in the tuning.

> But after an hour the overall tuning start to get up and down (a very slight change) slowly.... I believe that some specific part changes its value due to heating ? I checked the +15/-15/+5 voltage line as it happens, and they are very stable (meaning the tuning will rotate while the voltages will keep on being stable).

Huh... others more versed on the J-4 than I will need to chime in...

- Aaron