Ken wrote:
If the unit works on batteries but not on the adapter, then it is
probably safe to assume that the power the unit needs is not being
provided by the adapter. This could be due to a faulty adapter or a
regulator circuit in the unit that is not converting the input from the
adapter properly. There might be a bad rectifier, bad capacitor, open
conductor, or any number of faults even if the adapter is good. Only by
opening up the unit and taking measurements can you arrive at the reason
it will not work with the adapter.

There is one thing to check first. Most of the time, there is a small
switch to switch off battery power when you connect an adapter. This
switch is often integrated in the connector, and could be open.

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Met vriendelijke groet,

Maarten Bakker.