The device will only use as much current as it needs to, to operate.
As long as the voltage is the specified value i.e. 12V then using a 12V 3000mA adapter won't be a problem.
The problem with using the 1500mA adapter was that it couldn't supply enough current.
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As you didn't specify the model I'm assuming that it uses an adapter with a [https://www.accesscomms.com.au/power-supply-symbols/|centre pin +ve output connection] as this is the most common connection.
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If the adapter has a centre -ve pin output connection it will damage the HDD electronics.
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The polarity of the output should be shown on the adapter case.
Hi @roboscrap
The device will only use as much current as it needs to, to operate.
As long as the voltage is the specified value i.e. 12V then using a 12V 3000mA adapter won't be a problem.
The problem with using the 1500mA adapter was that it couldn't supply enough current.