Are there cases of damage to the rig involving the SMPS's
that result in anything other than D109 failing as a short?
If not, perhaps all that's needed is to have a few spare zener's on hand.
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Does the zener on 5v ever get nailed?
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Of the four short term solutions I suggested, the SCR clamp
might be best because it is the simplest and most foolproof to apply.
Works like a zener by shorting out the supply, but recovers when power is removed.
Can be designed to have a more accurate trigger voltage than a zener,
operates faster, and could handle more current without damage.
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When the 3.3v rail is shorted to ground by either D109 or this new SCR clamp,
the STM32F drops PWM_3V3 and PWM_VCC and everything shuts down.
When an SCR clamp brings down the 5v rail, the STM32 might still be
running PWM_3V3 and PWM_VCC, burning out Q103, Q105, Q108 and L101.
So perhaps best to build both clamps on one board, a high detected on?
either 3.3v or 5v causes both SCR's to trigger and bring down the rig.
This board requires connections to 3.3v, 5v and ground, could plug
into JP103 or JP105 for those connections so no soldering required.
Note that 3.3v is enough to power an op amp and a precision voltage reference.
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Jerry, KE7ER
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On Mon, Oct 21, 2024 at 01:42 PM, Jerry Gaffke wrote:
Short term solutions include:
