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Ive seen circuits that use reverse biased diodes connected from ground to the plates of output tubes as “transient spike preventers”. How does this work?

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Ive seen circuits that use reverse biased diodes connected from ground to the plates of output tubes as “transient spike preventers”. How does this work?

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The 1N4007’s serve mainly as an amulets against the voltage gods in this case. An inductive flyback pulse will go to literally ANY voltage until it finds a discharge path. Ideally, transients that would cause very high positive voltages on one push-pull plate would cause high negative voltages on the other plate, and the diodes on the negative going plate would clamp the voltages on the positive going plate through the output transformer. This does indeed happen for small, extremely-tightly coupled transformers. However, any leakage inductance between the two primaries prevents the tight coupling that would let the negative going diodes protect, and worse yet, it’s the leakage inductances that cause the spikes on transients anyways. What really happens is that the first few flyback pulses that occur will break over the 1N4007’s rather than than arcing the plates on the positive side, so there really is some protection, it’s not just where it looks like it is. If you’re lucky, the 1N400

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