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.

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.

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.

Simply bend the pins a little. Then when you plug the cord in, it will make a tight connection pushing against one side.

Same thing works on old electrical wall sockets, that won't hold the plug well anymore. Bend the blades out a little and it gets good connection again.

I tried that, but unfortunately bent the ground pin a bit too much. It collapsed when I tried to connect, and wouldn't let the connector go in far enough to connect.

You've just revealed to me, though, that the other one is either a good subject for that experiment, or it's trash. I might as well do the experiment!

Is each pin solid? Or is it possible to spread the pin(s) apart? If they able to be spread apart, then that would work better than bending it to one side or another.

KOT

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?


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.



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.

I did not buy these from Lenovo, but the new supplies and the old supply are labeled 65W 20V, and are Lenovo brand.

The computer is a T420. When I'm using it on the desk for extended periods, I plug in the power supply and leave it attached. Recently, while working in a 203VAC area (not US), the power supply seemed to be hotter than I had ever felt it. I switched to running off the battery or turning off the computer and charging the battery. Then I noticed that the air coming out of the vent was scorching.

I thought I'd see if a new battery would help, as I was only getting about an hour of battery life. I bought (back in the US) a replacement, non-Lenovo battery. Heat conditions remained the same though battery life improved.

Just in case the original supply (oops: I bought the computer used about a year ago, so I don't KNOW the "original" supply was the original supply) had been the problem or had been damaged by overheating, I bought the two Lenovo supplies we're talking about here.

When I was searching for the proper supply, I found that various oversize batteries were available, with appropriate power supplies. I finally found and bought that matched the original in rating.


Wait: that's what I said I thought it was doing, and here you're proposing that it's possible, as though it's a new idea. Wha?


It says it does.


Yes, I absolutely could be mistaking this.

A confusing fact is that sometimes the supply is working great, but upon moving it slightly, the power turns off (computer beeps to indicate loss of charger power); subsequent moves appear not to cause power to come on or off. You know I have troubleshooting experience, so I recognize patterns. As far as I can see, this foldback idea matches the details as well as mismatched connector parts after heating.


I've discussed the charging circuitry with a repair vendor. There's no replaceable charging circuit per se in the computer: the charger connects via a cable to the battery.


Yes. Any one of these supplies work with the laptop, either with or without the battery in place (which reveals that I was wrong: the charger doesn't only connect to the battery; it also connects otherwise to the computer).


Because battery life was down to about a half hour and suddenly (to me) the power supply was HOT as compared to warm. It felt like about 102 degrees F.


I did, and it does. And I bought the new supplies in case the original one was somehow damaged but not destroyed by whatever was making it so hot.


These are Lenovo, with the possible exception that someone is putting Lenovo labels on other batteries and selling them through Lenovo distributors.

I have since found a program that shows me the core temperatures, and it's pretty amazing to watch! Sometimes I'll be doing nothing, though of course the computer is doing what it does, and the cores will go up to the high 80s; other times I'll be downloading pictures or something else that I fancy takes a lot of computer power and the cores will sail along in the 50s or even 40s.

Meanwhile, I've cleaned the fan and replaced the silicone grease on the processor... a power saving power setup seems to help the most, though there are still heat spikes and the supplies run warmer than I think they should.

Brian, you never commented at all on my main comment: that the power cords seem not to be matched to the power supplies; the power supply pins appear smaller than the power cord socket sleeve arrangement.

KOT suggested that I might spread the pins out a bit for a better fit. I don't think that's possible without a great likelihood of breaking them. The pins look like nickel-plated pins I've seen where a flat piece of metal is formed into a round shape, then the ends are pushed together to make a rounded point. You mess with expanding that at your peril; in addition to the shape not lending itself to such bending, the metal is kind of brittle.

So, back to the subject: anyone ever run into power cords that seem not to fit the pins in the device?

That is the corrrect wattage and voltage for the model, so should work, as long as the supply is really putting that out. You can check the voltage easy enough with a voltmeter.


This hints that something in the PC is running pretty inefficiently. The external AC adapter itself (some people call it the charger... it is not... the charger is in the PC.) puts out the same voltage, 19V. It is common for the AC adapters to feel too hot to most Americans when running off 203 or 240Vac, it's just a function of how they're designed.

As you've replaced the original battery, and battery runtime has increased, I suspect the charging circuitry is working ok.

I don't think the prongs on the AC adapter cord not fitting super well into the AC adapter socket on the supply will cause any issue with causing more heating in the laptop.

So you might have more than one issue.

I can't rule out you getting some cord that doesn't work well. But your posting seemed to indicate that multiple adapters had this problem, which I will assume is pretty unlikely, unless you're using the same cord with them all. (In which case it might be what is in common... the cord.) I do normally see pretty big tolerances in the molded connector on the cord that plugs into the adapter. The holes being much larger than the pin, does not surprise me. Inside are two beryllium copper springs which press against the pins to make contact, so it is not a very picky thing from a tolerance perspective.

The computer itself getting hot, seems like a separate issue. I doubt that the hot air coming out is a function of bad contact between the heat sink and processor, if that were the case, the fan would start to fully spin up, and you'd likely get very little heat out, while the system acts really sluggishly. If it does this, if you removed the heat sink from the processor, it is possible you have some voids in the thermal grease. I like to spread a very think coating, and then once putting the heatsink / heatpipe / thermal spreader assembly back on the processor, wiggle it a bit in both x and y planes a bit, to make sure to get rid of any voids in the paste.

Having the air coming out be hot sometimes is not a sign that something has to be wrong. If the processor is turboing, it may be consuming 40W or so, add the display backlight, and other circuitry, and you'll end up close to 65W. Think how much heat a 65W bulb puts off, and now think that is getting blown out a little air vent... yeah, the processor running at full speed for a time, is going to blow some pretty hot air.


That could be something inside the supply as well. Wouldn't be the first time I've seen a little solder ball or piece of metal trapped under a component, that when you move the item, it can short something important.


Yes, the charging circuits are on the main board. If it is some issue like the magnetics for the charging circuit are cracked, and therefore dissipating lots of power, there is no cheap easy fix. All the places I've ever run into just want to do a full board swap in such instances. If the unit is out of warranty, you will be better off replacing it, that trying to get it fixed. I'd use the system, and make sure you have a full backup of any data.


That's 102F is a bit under 40C, which is what I believe is acceptable according to UL for the surface temp of these supplies. So that is likely ok. These small supplies do tend to run warm, as they are about 85% efficient, so that wasted power is being radiated out from a smaller box, so it gets warmer.


What you think takes power, doesn't necessarily. Downloading takes very little processor power. But things like encrypting the data over an SSL connection can be quite processor intensive. The high 80s C is about the max you want to see for a processor. As long as it doesn't go over 90C and stay there for minutes you are ok. If it is in the 40's and 50's C, you are just fine.


I'm guessing you did this ok, or you likely wouldn't be feeling warm air blowing out of the portable, and the processor temps would likely stay much warmer, and you'd likely be complaining about how laggy the interface seems.


I did talk about this above in this post. I've never seen this be an issue. So I doubt it is. But, there's a first time for everything.


Yeah, you'll destroy it before you can bend them enough to matter. If you think it's the cord, more specifically the contacts inside the cord that mate to that pin, buy another cord.


Nope.

I would not bend the pins on the computer, but I would take the plugs and with an ice pick or other small appropriate tool crimp the plug side down tighter. I did that years ago on boom box cords that got plugged in and unplugged repeatedly.

All the comments above this one are accurate and/or good advice.


You write "multiple adapters." I used no adapters.
I used multiple cords, but they were from the same supplier and probably from the same manufacturing batch, so I'd expect them to be the same size as one another. That's why I'm asking others about this -- I'll bet nobody out there has bought power cords from the same batch as the two I got two months ago!

The holes look larger than the pins when you look into the holes. When you can look into the holes, those springs are in the position that makes their inside measure the smallest, since they don't have any pins inside them pushing them apart.


Yeah, that sounds good, but when you push the heat sink in place, pins lock it so that it cannot be moved x and y. All you can do is remove it and replace it in the y direction.


As for the silicone, I know voids can be a problem, but paraphrasing you, if I'm getting scorching hot air out of the fan, then heat is definitely being pulled out of the processor!


Both supplies, using both power cords, do the same thing.


Oops, typo: I meant 120 F, which is 49 C.



It's mostly in the 60s to 80s. I think it helped to change the power plan to saving power.



Thanks for answering the main question!