[Commotion-dev] TP-Link WDR4300 with more than 12V power supply

[Ben West]

The regulator circuits on the TP-Link that develop the 5V, 3.3V, and
whatever other logic supply voltages from the bulk 12V will usually have
rated tolerances of up to 2x the stated input (e.g. 24V).  However, the
reason for designing in these tolerances is to ensure a reasonable life
span for the power regulator's electronics, and also to elegantly tolerate
variation on the actual output of the mass-produced 12V wall-warts (which
may range 9V to 15V).

Subjecting the unit to substantially greater than 12V will shorten its
life, and it may even lead to overheating in situations where ambient temp
is high (e.g. an enclosure w/o ventilation).  Similar for powering it with
substantially less than 12V, as the DC-DC on the TP-Link will then have to
draw more current to supply the onboard voltage rails, possibly exceeding
component ratings.  (Which is when the magic smoke appears.)

In addition, the 15V supplies you're trying out will themselves have
variation on their output.  Some may put out 18V or 20V and fry a unit.  A
way of capping that output to 15V would be good.
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