65w power supply center pin question

[paramount]

Hi,
My question relates to the safety of adapting power supplies for use with a different computer.

I have a couple of old Lenovo ThinkPad 65W 20V power supplies with the big barrel connectors. Model numbers:
supply #1: 92P1156 (FRU 42T5282)
supply #2: 42T4422 (FRU 42T4423)
The big barrel connectors have a center pin, which I understand is for the computer to sense the wattage of the power supply.

I want to use these two power supplies as spares to power my Lenovo Yoga710-14ISK. The Yoga710 OEM is powered with a 65W 20V power supply that has a 4.0 x 1.7 mm 2 pin connector. Models with a discrete graphics card (which mine has) come with the 65W power supply, while models without a graphics card come with a 45W power supply.

I purchased the following adapter tips, which have a proper hole for the male center pin on the big barrel power supplies.

https://www.amazon.com/gp/product/B08H4 ... UTF8&psc=1
"EBTOOLS 2PCs DC Power Jack 7.9 x 5.5mm to 4.0 x 1.7mm Plug Connector Adapter Notebook Accessories for Lenovo"
The info for these adapters indicates they are for 90W power supplies, but there are no details about the circuitry (or lack thereof) surrounding the center pin.

Can I just go ahead and use these adapter pins with the Thinkpad power supplies and plug in to my Yoga710 with no issues?

The following forum post has some info, but I don't know how to apply it to my situation.
viewtopic.php?t=116525

Is this analysis valid? "The center pin plugged into the adapter is not connected. Therefore, the computer has no way of sensing which power supply it is connected to, other than the innate voltage/current/resistance from the supply itself. And since the supply has the proper current/voltage rating for the computer (matching the OEM power supply), then everything should be fine."

[axur-delmeria]

The way Thinkpads detect the charger's wattage is by measuring the resistance between the center pin and ground. See: http://thinkwiki.org/wiki/Power_Connect ... _connector

The Yoga only has a 2-pin connector, and doesn't (and can't) know the wattage of the charger).

IMO the adapters you bought will run fine, since they're built to handle 90w. It's very likely that the center pin in those adapters isn't connected to anything.

[atagunov]

I have a couple of old Lenovo ThinkPad 65W 20V power supplies with the big barrel connectors. Model numbers:
The big barrel connectors have a center pin, which I understand is for the computer to sense the wattage of the power supply.
I want to use these two power supplies as spares to power my Lenovo Yoga710-14ISK. The Yoga710 OEM is powered with a 65W 20V power supply that has a 4.0 x 1.7 mm 2 pin connector. Models with a discrete graphics card (which mine has) come with the 65W power supply, while models without a graphics card come with a 45W power supply.
I purchased the following adapter tips, which have a proper hole for the male center pin on the big barrel power supplies.
https://www.amazon.com/gp/product/B08H4 ... UTF8&psc=1
Can I just go ahead and use these adapter pins with the Thinkpad power supplies and plug in to my Yoga710 with no issues?
... since the supply has the proper current/voltage rating for the computer (matching the OEM power supply), then everything should be fine

Fully agree. If the voltage is correct and power supply's wattage is about the same or bigger than the original you will be fine. I'm taking your word here that the OEM Yoga710 PSU is also 20V

The centre pin is not connected to anything inside the PSU, so PSU has no idea if the consumer is making any use of the pin. I understand the centre pin is connected via a resistor to one of the other metal contacts right inside the round barrel plug. If you had the right plug for Yoga you could cut off the round barrel from an old adapter and solder on the new plug - provided the polarity is correct. The cable from old PSU to plug is in my understanding just 2 wires. The adapters look fine too.