I need to know the polarity of my DLink DI-704. Is the center post of
the power input + or -?

I have the user manual it only states 5VDC. The amperage is listed as
1 in the front of the manual and 2 at the back of the manual. Polarity
and amperage are not indicated on the unit itself.

Is there a way I can determine the polarity of the power inlet, using a VOM?

Well the AM Radio in my '70 Hemi-Cuda has red/black power leads.

Hope that helps.

As this is not a CentOS support query, this thread has been moved to Social.

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Do you still have the original PSU? Is it working?

If "yes & yes", then just power up the PSU and apply the VOM probes.

From my recent observations, every PSU that I tested supplied +ve on the inner and -ve on the outer sleeve of the barrel.

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I have just searched Amazon for the string D-Link DI-704 router replacement power supply. The results I have obtained are for the U.K. -- so try it in your own country.

Nearly all devices are positive tip.

If you have the power supply, you can easily determine the polarity. If you don't, then you have three choices:

1. Contact the manufacturer.
2. Open it up, and inspect the circuit.
3. Try positive tip and hope for the best.

Positive-tip is so ubiquitous that I just go for #3, and it hasn't let me down yet. Of course, your mileage may vary.