Flaky eBay buck converter

[netdudeuk]

Ok, so I bought one of these http://www.ebay.co.uk/itm/351020297464

I wasn't expecting to be able to push it to the specified limits but it didn't even pass any tests.

Hooking it up to my DP832 with a multimeter on the board's output, the output voltage always started just below the input voltage and went on to rise to a higher voltage.  For example, 15v in produces 16v out.  According to the DP832, only 13mA was drawn in this example.

Adjusting the pot made no difference at any time.

No heat generated at all.

I know that this is a cheap board so it's not about the money but I would be interested from a learning perspective if anyone has any ideas about what's been going off with it.

Can these and similar boards ever be trusted ?

[dexters_lab]

likely  just a faulty one. Email the seller they will probably just send you another

[rolycat]

It's unusual for the output voltage to be higher than the input, but have you read this thread?

You need to turn the trim pot anticlockwise a lot.

[tom66]

I wouldn't be surprised if the internal switching transistor is shorted.

[electr_peter]

It's unusual for the output voltage to be higher than the input, but have you read this thread?

You need to turn the trim pot anticlockwise a lot.

Turn the pot (it is misleading at first) and do more tests with various input/output voltages and load currents. There is not much that can fail in listed DC/DC converter.

[con-f-use]

The exact same module is sold almost everywhere in china. It functions reasonably well. I'd say, you either have a shorted leg or something is wrong with the trim pot or yours is faulty.

[netdudeuk]

Thanks for the replies including the reference to the previous thread.  Rolycat got it right