I measure 10.0 kOhm between the outer metal cylinder and the center pin on my 65W PSU, regardless of whether the power connector is plugged in or not. This would suggest that there is just a resistor between the center pin and earth, probably somewhere inside the tip.

Lenovo Power Manager correctly reports it as a 65W PSU.

20.2 V potential between inner and outer cylinders. Not that it matters.

The third-party PSU I bought has a detachable tip. It has infinite resistance between tip and ground, regardless of whether it is joined to the PSU cable or not. This would suggest that there is no contact between center pin and earth anywhere.

Lenovo Power Manager reports it as a 90W PSU, while it is actually a 150W unit.

zsero writes:


What is a "normal TP adapter"? 65W?

Anyone with a 135W unit around care to make a measurement?

Thanks in advance
/Some guy

I think all thinkpad adapters are 10K, except the W520 one which is 1.5K. I don't know about the 135W one. I think you can just insert a 1.5K resistor into the back of the laptop and use the generic adapter. Do you want to try it?

Good point. It doesn't matter if the system believes it to be 135W or 170W.

I shall try it as soon as I get the time. Have to do some things first that require an unexperimented and undestroyed power tip. Check back in a few days.

summary:

65 watt



http://forum.thinkpads.com/viewtopic.php?f=30&t=92127&p=603576#p603576



http://forum.thinkpads.com/viewtopic.php?f=48&t=94554&p=679798#p679798



http://forum.thinkpads.com/viewtopic.php?f=48&t=94554&p=682578#p682578



90 watt



http://forum.thinkpads.com/viewtopic.php?f=48&t=94554&p=671815#p671815



http://forum.thinkpads.com/viewtopic.php?f=48&t=94554&p=682578#p682578

I can confirm that the signal pin is not connected to ground.



135 watt



http://forums.lenovo.com/t5/W-Series-ThinkPad-Laptops/Lenovo-W510-with-90W-adapter-Reduced-Performance/m-p/351845#M12703



170 watt



http://forum.thinkpads.com/viewtopic.php?f=48&t=94554&p=679798#p679798



230 watt

Anybody have a source for this one?

OK I can just confirm, that I measured 4 different 65W adapter and all of them were 10K.

Right. I am confused.

I got myself an adjustable potentiometer and soldered it to a butchered power tip. Changed the resistance around a bit and looked at what Lenovo Power Manager said under the Battery tab.

These are my findings:

0 ohm = 120 W
1500 ohm = 120 W
2000 ohm = 120 W
2500 ohm = 50 W
3000 ohm = 50 W
4000 ohm = 50 W
5000 ohm = 50 W
6000 ohm = 50 W
7000 ohm = 65 W
8000 ohm = 65 W
9500 ohm = 65 W
Infinite ohm = 90 W

The last one I did not measure, my trimpot only went to 9.5k.

So... what's the deal with the 135 W and 170 W adapters?

Here are some pictures:

Oh, hey - the W510 reports the PSU as 135 W with 0 ohm?!?

I did the first list on my x61s. It apparently differs between computers!

Note: The x61s uses the latest Lenovo Power Manager, so it cannot be a software thing. I suppose the BIOS tells the Power Manager the wattage and the x61s was never expected to run from a >120W PSU.

Or something.

I shall make an updated list on the W510 once its drained battery gets charged. I need to unplug and tweak the trimpot every time, just twisting the screw when it is connected to the computer makes no difference in the wattage note.

This is what I got from the W510:

0 ohm = 135 W
1000 ohm = 135 W
1500 ohm = 135 W
2000 ohm = 135 W
2500 ohm = - (empty watt line, but it says "charging")
3000 ohm = - (empty watt line, but it says "charging")
4000 ohm = - (empty watt line, but it says "charging")
6000 ohm = - (empty watt line, but it says "charging")
6500 ohm = 65 W
9500 ohm = 65 W
Infinite ohm = 90 W

My interpretation:

< 2500 ohm means "max capacity PSU". This should be tested with a 170 W and 230 W system as well.

2500 to 6500 ohm means 50 W which for the W510 is too little to be of any use so it does not report any PSU at all. Although it does say "charging" further down on that tab, the remaining time fluctuated wildly.

> 6500 ohm (but less than some unknown high value) means 65 W.

No connection means 90W.

So there you have it - if you want to modify your power connector so that the system thinks it is a full-powered unit and does not throttle the CPU, just short-circuit the center pin to ground.

I take no responsibility for anything you may destroy. I suspect that you may blow a lesser PSU or make antimatter shoot out of your USB ports or whatever, so do not rely on me for accurate advice. I am not educated in electronics and most of what takes place under the plastic cases of electric devices are magic to me.

Since I had a bunch of power tips, I ended up doing this:


I might add that my PSU is a 150 W unit (noname brand, but still), so do not expect it to cause any problems.

X61s is two years older than W510. In the time when ThinkPad generation α61 was engineered and produced, only 65 and 90 watt AC Adapters existed. I think, their power subsystem is unable, or not programmed, to detect newer power supply signals. W510 is not only newer, but specifically made for use with the 135 watt supply. W520's 170 watt supply is even newer, and so it will probably be recognised as 135W by a W510.





I think, the elusive 230 watt adapter is in one of the uncertain ranges.

Did you have that table this whole time? =/

This is excellent sleuthing, Stinkpadda! Very useful indeed, and fits perfectly with all the previous findings of others. It looks like automobus pulled that table together as a summary of your results. I have a W520 and I also have one of those 90W tips from a cheapo adapter, so I'll see if I can replicate the same result by shorting the centre pin to the outer-casing wire and will report back (with fingers crossed that I don't blow the W520 power port!).

It's such a pity we have to short with the _outer_ part, as if we had to short with the inner one, we could just put some tiny wire at the back of the computer and use any adapter!

Unfortunately, the el cheapo 90W tip I have is exceedingly difficult to unravel. Having scraped/cut away as much of the plastic as possible, I'm left with a prong connected to the middle pin, but coiled around this extremely tightly is a sheet of metal connected to the inner face. There seems to be a thin layer of plastic insulating the two, but there's not enough space to solder without shorting the inner face and the middle pin. I'd have to try to melt some of the remaining plastic out in order to get a purchase on the coiled sheet and prise it off, if it can be separated at all. Won't now be able to do this for a couple of weeks (going on holiday), but will report back if I manage to get anywhere further with this tip. Does anyone know a good source of tips that might be more easily modified?

I should just say, too, that this cheap tip originally had the middle (signal) pin connected to the inner face electrically, and my W520 detected it as a 90W. This seems to be very dangerous to say the least. If anyone adopts the solution of shorting the pins inside the computer, all I can say is, beware of cheap tips, because that would have shorted the + and the - as well, and could well blow something vital either in the adapter or the computer.

Thank you, geoffrey, for the warning about dangerous aftermarket DC plug tips.





Thank you, Stinkpadda, for your experimentation. I very much appreciate your findings. I just found a relevant article in the Lenovo Community Knowledge Base.


Lenovo Thinkpad Power Adapter compatibility list
(print view)

What's the affect on power demand if I go into the bios, turning off two cpu cores, and using integrated graphics (ie. travel mode, turning the W520 into a T520). It would be really nice to carry a 90W slim adapter instead of the 170W brick we all complain about.

Don't worry about the power demand, I've never seen my W520 > 30W. And even if for some fairy tale reason you are able to push > 90 W out of a W520, your power supply won't explode, it will just drop voltage, thus making your laptop use the battery.

I'm also getting the similar results without handicaps using Kill-A-Watt to test, but am wondering if those handicaps mentioned (turning off 2 cores, using integrated graphics) will allow the 90W adapter to actually charge (not drain) the battery. Also, does the 90W adapter jack fit the W520? 170W to me seems overkill. I have to carry this thing around every day and am looking to lighten the load. In comparison, I saw a 65W power a T500 and needed a microscope.

Look, the W520 normally uses around 10-15W. So yes, the 90W adapter will definitely charge it.

I couldn't agree more in all practicality/theory, but I think the consensual complaint is that the 90W doesn't charge when in use, likely because of a bios restriction that Lenovo should lift. Have you tested it?

That's why you put in the resistor I haven't tried it, because I thought it's easier to buy another 170W and keep it in the place where I'm using my laptop. But the resistor trick is very very easy!

In everyday use the W520 is definitely not using anything like 90W. The problem is that the firmware refuses to draw any current at all from a 90W unless the computer is asleep or off. This is why we have to trick the computer into thinking that at least a 135W is connected, and the way to do this is well documented above. The problem is cutting open the tip without destroying it. I destroyed one cheapo tip trying this. The other solution is to swap the cables between a 90W and 170W. Ideally some kind of plug system (one which prevents you reversing the polarity), so that you could use the appropriate adapter for whatever scenario you have.

This guy is selling Lenovo 170W with NO center pin: http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... TQ:US:1123. What do you guys think THAT is all about. I asked the seller and he replied:

> You will have to get that answer from the manufacturer because they made two kinds of them one with pin and one without.
> I am only describing the item as it is.Some machine do not require the centre pin and some does.So check your machine manual
> of the manufacturer website.
> Thanks

If this adapter would actually work, maybe the simplest way to add resistance to a 90W center pin is just to remove it.

Are these tips three conductor -- outside, inside and center?

BTW I bought Chinese knockoff 170W adapters on eBay and they came with standard 20V tips -- not all the extra plastic. Seem to work fine on a W530.

Well, let's take a closer look at the item description.



I think W700 has a different power connector than ThinkPad α60. Now I am even more curious about the 230 watt supply.

And I also think, between the old 5.5mm plug, the W700 6mm plug, and ultracheapsubnotebooks ("netbook") with 2.5od • 0.7id plugs, that leNOvo had even less reason to invent their rectangle connector.

They had to invent something rectangular after the new circular keys.

ThinkPad W70x adapters have no centre pin (and they use a different size barrel shaped connector to the regular Lenovo ThinkPad)

I found a X1 Carbon and its 90 watt AC Adapter. Its resistance signal is about 550 ohm. Does anybody have a opportunity to check a rectangle 45 or 65 watt supply signal?