On Mon, 5 Feb 2018 13:06:26 -0000 (UTC), Gordon Henderson
 wrote:


> If you have a screen connected then you'll see a yellow "lightning bolt" icon
> appear if the power is too low (and a red thermometer icon if it's too hot)
>
> 99% of issues like this is the power supply. Change it. Try another,
> and if you have one, get your multimeter out and measure it when
> it's powering a Pi.

I agree, and I'd like to add that many USB cables have very thin
wires and are too long, so they have too much resistence and cause
unacceptable voltage loss. The buffer capacitors in the Raspberry
Pi are too small to even supply short peaks current demands, so
every peak has to be supplied by the power adaptor.

I replaced those cables with a "charging cable", they just have
thick power wires, no data lines, and haven't had any problems
ever since (RPi 3, with an USB harddisk that draws 500 mA).

Search on eBay for "Micro B USB Fast Quick Charge Cable 2.1A
Android SmartPhone 18AWG" from Korea (or equivalent).

Although the offer states 2.1A, they will carry 2.5A with ease.
I prefer a length of 15 cm or 30cm.

Not cheap, but really good.
--
Regards,
Kees Nuyt

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