I'm working with an IBM ThinkPad A20m laptop. The internal battery is dead and it seems the power adapter is also nonfunctional. I checked the cable from the outlet to the converter box and got 120V AC. However, I got no DC reading from the converter to the barrel plug. I tried for a day wiggling the cable to see if all at issue was a minor short in the wire. Still no power.

I have another power adapter that originally shipped with an Hp laptop that fits the plug for the IBM. However, I thought I would check whether the two are compatible.

The original IBM power adapter is rated at OUTPUT (16V DC 4.5 amps)
The Hp power adapter is rated at output (19V DC 3.16 amps)

Both input cables have a yellow ring around the plug end that interfaces with the laptop. I was not sure if the color had any bearing on the ABILITY to SWAP them with different systems.

Thanks for your help!STOP. Don't do it.

You cannot use a 19v supply where 16v are EXPECTED, even if the connectors HAPPEN to be the same.

Here are some of the bigger reasons:

1) The polarity could be different between the supplies. If it is: zap, lappy deceased.
2) The 19V supply will cause the internal regulators to have to dump extra voltage, which is given off as heat. It will likely overhead the regulators soon and ultimately damage the laptop.
3) The current rating on the 19V supply is lower because it provides extra voltage. Unfortunately, that extra voltage is wasted on a 16v laptop so the power supply wouldn't have enough power to keep the laptop running.

In short: buy a new supply made specifically for that laptop.

RaydudeThanks, RayDude,

I have ordered a power adapter suitable for the Thinkpad.