I've just completed a couple preamp boards by Greg Ball - called the SKA Pre. Each channel is on a separate board. One board works fine. The other seems to be oscillating at about 14MHz but only with the input shorted. In other words, with the volume potentiometer turned for minimum (i.e. input connected to ground) the oscillation is at its maximum. As the volume potentiometer is turned up, the oscillation disappears. Attached is the schematic. Any suggestions will be appreciated.
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I'll give it a try in a few minutesYes, if you stand that new resistor on end, then the end with the short lead should go
to the bases of the input transistors.
Oscillation can be caused by feedback that is not carefully controlled. A lower frequency pole
(from the added resistor) reduced the net HF phase shift enough to restore stability.
An introduction: http://ocw.uc3m.es/tecnologia-elect...-1/Lesson2_Stability_in_Feedback_Circuits.pdf
(from the added resistor) reduced the net HF phase shift enough to restore stability.
An introduction: http://ocw.uc3m.es/tecnologia-elect...-1/Lesson2_Stability_in_Feedback_Circuits.pdf
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