I've been wondering why some people regularly blow BS170s and the associated ICs while others don't.? Could it be how people are powering their devices?
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If a user has a non current limited supply, such as a battery then a momentary glitch in the system , for example TX being active while CLK2 is not running while the DAC power is active, could cause high currents through one bank of the BS170s.? There's no inherent current limiting and it would not need excessive voltage.? It would only take a few milliseconds, that could make it difficult to spot.
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People using current limited power supplies - limited to around an amp - could be largely immune to over current failures because the current limit would prevent them.
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The power modulator seems to be derived from the one in the 5W HF PA kit, the difference is mainly that the PA kit has foldback current limiting and the QMX PA modulator doesn't.? Would having hardware PA current limiting help to preserve the output FETs?
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