[R-390] R-390A calibrator oscillator

[Drew P.]

John Saxon wrote:


"...I am working on a 390A to sell.  It is pretty much ready to go, but the 100KC calibrator has a "raspy" sound rather than a more "pure" sinusoidal sound."  

The 100KC calibrator consists of a free running 100KC multivibrator injection locked by a 200KC crystal oscillator, plus a cathode follower. I encountered the same problem once - raspy calibrator note, and drifty calibrator as well.  Problem was a bad 200KC crystal - the multivibrator went uncontrolled.

Drew