Power light flicker on Class-D board - capacitor needed?

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I have one of the Sure JAB TPA3116 boards which has an onboard power LED.
When powering the board with a 12V, 1A power supply the LED lights up solid green.
However, when I try powering it with either of two 19V laptop power supplies (Lite-On brand) the LED is dimmer and flickers continuously. The board still seems to drive the speakers OK.

Do I need a capacitor across the power input? If so, what spec? Or is there something else going on here?

Thanks!
 
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I'd say something else was going on but wouldn't like to what without knowing how the LED was wired, and also without looking at both supplies on a scope. Some SMPS used to need a minimum current draw in order to regulate correctly.

So lots of possibilities but without knowing the above it would all be guesswork.
 
Thanks for the ideas. Oscillation of what? The power supply's output?

With a 2200uF electrolytic across the power input the LED is still flickering. Also tried a third 19V PSU, a Sony one from a TV and the same flickering occurs.

The LED is labelled D4 in the centre-left of the board photo, just below the 330 inductor:
http://www.parts-express.com/Data/Default/Images/Catalog/Original/320-3519_ALT_1.jpg
It's near the CN3722 charge controller so could be to do with this as you suggest DM.
 
It's the charger..

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