Re: sBitx Developer¡¯s Edition (v1) ¡ª how to protect the RPi4?
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It depends on what upgrades were installed. I would first remove the raspberry pi and check if that survived, then regulators (AMS1117-3.3V) and the 5v regulator.
On Tue, Sep 19, 2023, 11:06 PM Dave New, N8SBE < n8sbe@...> wrote:
I had a 10 yr old Elecraft P3 blow up when the AMS1117 shorted the 13.8 VDC supply to the internal 3.3V bus.
Over $400 in repairs later (and a new revision power supply board in the P3), it's working again, but I found out that the 2KW TXMon that was attached to the P3 when the AMS1117 went out is also defective - it has 3.3V-fed surface-mount opamps in it, so I figured it blew out one or both of the opamps, as well.
Beware the AMS1117....
73,
-- Dave, N8SBE
On 2023-04-27 00:38, Shirley Dulcey KE1L wrote:
The first version of the QDX experienced high failure rates of the AMS1117 regulators (same basic design as the LM1117, different supplier). A major problem with the 1117 is that the most common failure mode is a SHORT, letting the full supply voltage through and typically destroying every downstream IC. Later revisions replace the 5V regulator with a 78M05, and run the 3.3V regulator from the output of the 5V regulator rather than directly from the power source.
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Different radio, but the experience with those regulators is relevant.
On Tue, Apr 18, 2023 at 4:55?PM ajparent1/kb1gmx < kb1gmx@...> wrote: Farhan,
ITs not the device loading its the posible reverse path due to that parts failure.
Fr example if that mosfet develops a gat to dran short then the GPIO pin
sees 12V and that's bad. the uln2003 fails or ther eis a board level short to it?
the relay select lines can fail at the Pi.
If everything works, its never an issue, only when something is wrong it becomes one.
As a development radio the expectation of >>>oops<<< should be foreseen.
--
Allison
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Please use the forum, offline and private will go to bit bucket.
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