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June 21st, 2025 07:55
Dell Inspiron 27-7775 Mains adaptor issue.
I have had the unit for about 5 years with no issues ! Suddenly on start up i receive a message stating that the mains adaptor is not genuine and a 330 watt dell adaptor is required ?? The adaptor came with the unit and is a genuine 330 watt unit ?? I cannot access BIOS as the unit will not boot shuts down straight away.
Any comments, help etc. appreciated !!
Thanks, Alan.
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anne_droid
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June 21st, 2025 09:03
Hi
Can you hold down a key, like F12, before applying the power?
ELSE try replacing the CMOS coin cell battery.
Mechman1
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June 21st, 2025 09:08
@anne_droid Thanks for the reply ! have tried all sorts of key combinations and replaced the cmos battery but no luck ? Even tried with an identical dell adaptor and still nothing ??
Totally weird for sure !!!Thanks for your interest !!
Regards, Alan.
anne_droid
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June 21st, 2025 09:33
@Mechman1
Hi
Hope this helps....
The internet reports...
Dell laptop power adapters use a third “ID” pin in the power plug to communicate the adapter’s wattage to the laptop. This ID pin is connected internally through a resistor with a specific value that encodes the adapter’s wattage. The laptop detects this resistor value and uses it to verify the adapter’s wattage and authenticity.
How the Resistor Determines PSU Wattage
Dell power adapters have three pins: Ground, +V (usually 19.5V), and an ID pin.
The ID pin is connected inside the adapter to ground through a resistor of a specific resistance value.
Different resistor values correspond to different adapter wattages (e.g., 65W, 90W, 130W).
The laptop reads the voltage or current on the ID pin (which depends on the resistor) to identify the adapter wattage.
If the resistor value is wrong or missing, the laptop may show errors like “Unknown Adapter” or refuse to charge properly.
Typical Resistor Values (Approximate Examples)
65W adapter: ~10 kΩ resistor on the ID pin
90W adapter: ~20 kΩ resistor
130W adapter: ~30 kΩ resistor
(Note: Exact resistor values can vary by model and generation; these are typical ballpark values.)
So I guess that if you have tried 2 then the fault is internal.