The new transistors are oscillating at about 1GHz, the frequency is frequency modulated by the incoming audio!
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The cure was a ferrite bead on the base and collector (now that's a first for me) and a 10pF SMD capacitor between base and emitter.
I grabbed my Tiny SA on a wild hunch, found a spike and borrowed a Signal Hound USB spectrum analyzer to confirm the oscillation.
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The semiconductor industry constantly "improves" their products.
Original 1N4004 switch slow enough to be a minimal EMI source, modern 1N4004 switch fast enough to be EMI sources from hell.? The silicon is purer, the junction is thinner and the turn off time is a lot faster.
Someday really soon I hope to post a simple test device to see how much commutation noise a diode produces.
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