Got mine in the mail yesterday. Nice little gadget for testing batteries outside of a device / instrument. I could not get it to work on any device by inserting the probe into the input/output jack of any device / instrument though. It either did not sense the insertion at all (and ended up doing a self-test), or displayed 'PL6' which indicates a dirty/faulty jack. I've tried it on my bass (Ibby SR900), tuner and a battery driven mixer. It kind of inserts very easily (almost 'loosely') into most of the jacks (almost as if the probe is too thin). I have not contacted the supplier yet as the manual states 'If you have tried both the output and the input of the device, and the test continues to fail, it may be that you have one of the few devices that does not work with the probe. Remove the battery and place it up to the external battery contacts to test it and verify that it is charged.' which is exactly what I wanted to avoid - I already have a multimeter for that purpose! Sending it back is out of the question as I will end up paying a lot more for the meter due to shipping fees from our continent to the States. Did any of you have similar problems?