Hi,

Does anyone know how to identify the Ground, Positive and Negative supply rail pins on the heads and/or PCB.

Yes.

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A backup a day keeps DR away.

Would you like to share your methods using the attached example?

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Sabo Computer Repairs & Data Recovery

The ground pin(s) is/are easily identified, either visually or by testing for continuity with a known ground.

Signal pins will usually have thin traces and will connect to the MCU or read channel IC, depending on the design. In particular, the Read/Write differential pairs are distinguishable as thin parallel traces.

There will be two heavy traces, usually located side by side, running to the motor controller IC. These will be the VCM pins. There should be a low resistance between these pins at the HDA connector.

Some newer drives have an additional piezo element for fine servo control. I'm not sure how to identify the corresponding pins, but I would expect that they would be driven by the motor controller or a separate IC.

The remaining heavy traces will most likely be the supply pins. Measure their voltages. Confirm that they are indeed supply pins by testing for continuity with the power supply regulators on the PCB. Many preamps get a +5V positive supply from the SATA power connector, usually via an LC filter. Your example does not show these regulators, so I can't identify the voltage test points.

_________________
A backup a day keeps DR away.

Thank you for the detailed information.

There are 3 coils. Measure the voltages at these points and test for continuity with the HDA contacts.

_________________
A backup a day keeps DR away.