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Old 20th Dec 2018, 5:56 pm   #8
Bazz4CQJ
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Join Date: Apr 2009
Location: Oxfordshire, UK.
Posts: 4,924
Default Re: Valve Multivibrator

Some time ago, I built a small test rig to draw Ia-Vg curves for valves which could then be used as standards for a valve tester. The first time I put in an ECC81 (with just one side hooked up), it started oscillating with no help at all from me. I had to go to some trouble to stop it; lots of ferrite beads on the leads etc.

I think it's Tanuki who occasionally points out that every amplifier aspires to be an oscillator. I think you can add to that that once a valve finds out it can oscillate, it prefers to do that rather than just amplify .

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