[sdiy] Weird JFET in Korg MS-10/20/50 style VCO

[lanterma at ece.gatech.edu]

Howdy y'all,

Consider the VCOs in the middle of this page:

http://www.korganalogue.net/korgms/images/service/ms20/circ1.gif

C2 (and the equivalent cap in the similar VCO circuit below it) appears to be an integrating cap for the VCO, fed by the current sinked from a C1583 NPN pair through a 10K resistor.

But there's also a JFET there (Q5). The current flows through the source and drain of the JFET, and the gate of the JFET is grounded.

Anyone by any chance know what the purpose of that JFET is?

- Aaron