VM202, how can I Iget it to work?

VM202
I have had two of these units, the first one did nothing, I returned it and received a replacement unit, this second one makes a buzzing noise when the USB with mp3 files is plugged in, but nothing else.
It is running on a 12v battery with the supplied black heat shrunk unit and 68R in place, audio output into a small mono amp that plays the output of a PDA playing an audio file from its audio output jack socket just fine. Also tried a ipod audio output, that is fine too. The only thing that I can get no music from is the VM202.
Any ideas?

If run from a 12V supply, it does not need the 68 ohm resistor, this is only for in-car use.
Please remove the resistor.
Did you try with a different USB memory stick?

I will try that. Can you tell me the purpose of the 68R.
I have tried several USB sticks all of which work fine in PCs. Does the mp3 have to be on the root of the drive, or in a folder?
If in folders how does it choose the order of play?
Does it use alphabetical or numeric order as first priority?
Thanks

I have removed the 68R and not much difference. There are two different rhythmic buzzing noises, one as I fit the USB stick for a few seconds, then it changes to a different rhythmic buzzing noise, or silence and I can select between these two options by using the controls. At no point does it play any music.

Did you try with a different USB stick?
If the problem persists, there is not much we can do about it. You can return the item for inspection/exchange.