On June 23, 2015 at 17:29, Ernie Gilman said...
I recently bought a couple of power supplies for my ThinkPad. The one I had uses a two-prong plug; these use three-prong mickey mouse plugs (IEC C5, I think). I was attempting to troubleshoot battery problems and needed to be sure it wasn't the power supply.
The fact that you recently bought these, and they are three prong rather than the more standard two prong, hints at what might be an issue. Did you buy these from Lenovo? Did you buy what Lenovo says is a direct replacement, or are these aftermarket, of some other brand?
If they are some other brand, did you make sure the supplies you purchased give the same voltage, and are rated for at least as much current as the supply that came with the PC?
Both supplies seemed to work at first, but then they would randomly turn off (I thought) and turn back on again. After much hassle I finally figured out that the openings in the power cords are on the order of .100 to .110 inches in diameter, but the pins in the power supply are around .080 inches! The cords simply do not always make contact.
That could be the cord if it isn't making contact. It could also be true if the supply does not have the correct voltage and/or current rating. These supplies implement what is called foldback current limiting. If too much power is drawn from the adapter, the adapter supplies a very low current. The idea is that if too much current is being drawn, it may be an accidental short, and dumping a lot of current continuously into the short could cause a fire. So the supply just uses a small test current. Some units look for the removal of the low impedance, and others require being unplugged from AC, at which point they'll again supply the rated voltage and current. Could you be mistaking an overcurrent situation caused by either a too low power AC adapter, as a bad connection due to the foldback current limiting?
The other issue is that the fault could be in the circuitry of the laptop itself. The laptop is designed to never draw more current from the adapter than the adapter is designed to supply, so the foldback current limiting never causes the issue.
It's possible that they made contact at first, but with normal heating of the supply, the metal deformed. I don't know.
Anybody ever run into this before, and have a solution? I'll bet the solution wouldn't be monoprice cords, but one never knows. Any help is appreciated.
So, does the original supply work with the laptop? The comment about "I was attempting to troubleshoot battery problems and needed to be sure it wasn't the power supply." also begs some questions. Why do you think you have a battery problem? Is this why you bought the new supplies? Note that if the portable has a removable battery, it will operate perfectly fine with no battery installed, as long as the AC adapter is working. So you might want to simplify your troubleshooting and get the battery out of the procedure entirely.
I have seen aftermarket supplies, that come nowhere close to their marked rating of what they'll do. The big brands like Kensington and Targus seem to be pretty good, but I've seen some others that are absolutely horrible.
