Will T21-23 power supply work with T41?

Message

alex001 · #1 Post by **alex001** » Thu Oct 30, 2008 11:24 pm

Hi All. Got a question regarding power supplies. I have three power supplies for my T21, and just got a T41 which came with a single power supply.

So, the big question is, can the T21 power supply(ies) work okay with a T41? Here is what is written on them:
T21:
input: 100-240V - 1.2A Max, 50-60HZ
output: +16V 3.75A

T41:
input: 100-240V - 1.5A - 0.9A, 50-60HZ
output: +16V 4.5A

From what I remember, it is usually safe to plug in a component if the voltage and amperage are lower, so by this standard it should be okay. However, am I asking for some kind of trouble by using a 3.75A power supply rather than the regular 4.5A? I don't want to shorten battery life, or, of course, the life of the laptop itself.

What I *do* want is a couple of spare/backup power supplies without having to buy new ones, if I can get away with that.

Whadaya think?

#2 Post by **rkawakami** » Thu Oct 30, 2008 11:50 pm

"Can the T21 power supply(ies) work okay with a T41?" No, it is not recommended that you use a power supply that has a lower current rating than what the laptop says it requires.

Check the bottom of the T21. It should have a current rating of 3.36A. You can use either the 3.75A or 4.5A power supply on that system. The T41's label should say 4.5A. If you use the 3.75A power supply on the T41 you stand a chance of either underpowering the laptop or overdriving the power supply beyond it's maximum rating. Doing so could result in a burned out power supply. It's not worth the $10-$15 apiece that it costs to pick up a proper 4.5A (72 watt) supply on eBay.

alex001 · #3 Post by **alex001** » Fri Oct 31, 2008 12:28 am

Thanks for the fast reply.

Makes sense! ...So much for my remembering that it is safe. Sounds like it won't burn it out immediately, but may damage it over time.

Only $10 or $15, huh? I didn't even check the prices. Ya, I see some low prices now that I'm looking. Okay, thanks again!

slaz · #4 Post by **slaz** » Fri Oct 31, 2008 7:15 am

Check the bottom of the T21. It should have a current rating of 3.36A.

Interesting .. just checked my T20, and it also says (on the laptop)
3.36A. But everyhting I can glean from online (e.g. tawbook) says the T-series shipped with 4.5A adapters. Does the 3.36A on the laptop mean the laptop _itself_ requires 3.36 (but might need more e.g. with a docking station ), or that a 3.36A adapter will supply the whole shabang, but IBM shipped 4.5A because those were just current production run at time of shipping maybe ?

Certainly I've used 3.36A adapters before now with the T20 and had no problems or excessive heat from the adapter ....

Interested because I have a few 3.36A original IBM adapters here surplus to requirements - maybe they can be classes as "OK for T2x-series" - surely would also be OK for X2x series - not sure about A2x series (more expansion etc.)

#5 Post by **rkawakami** » Fri Oct 31, 2008 2:56 pm

I would have to assume that the T20-T22 systems having a 3.36A rating can be safely powered with the 3.36A (aka, 54 or 56 watt) power supplies regardless of whether or not they are plugged into a port replicator or docking station. The current rating of the laptop should have been determined by the maximum amount of hardware that can be connected. This includes the PCMCIA and USB ports, which each have their own current supply limitations. Placing the laptop onto a simple port replicator will not significantly change the number or type of external connections. Some docking stations, on the other hand, can provide for a PCI card. That's why those docks have their own power supply which can handle 90 or 120 watts.

You might be right in saying that IBM shipped the early T2 systems with the 4.5A (72 watt) supplies as they were "current" inventory at that time. You can certainly use a 3.36A supply with the X2x systems since that is what they shipped with. Based upon the current rating I see on my A22p systems, you should also be able to use it with this system as well, even though the tawbook says they shipped with the 4.5A supplies. If in doubt, do what I do: only use the 4.5A supplies with any of the 16V Thinkpads.

exTPfan · #6 Post by **exTPfan** » Fri Oct 31, 2008 7:05 pm

Yes it will. 16v x 3.75a=60watts. Your T41 will typically use only about 20 watts, and it will be difficult to get it anywhere near 60 watts.

There are people on this forum who warn against using anything but the officially recommended power supply, but there are also lots of us who do it, and not a single report of any damage to a computer.

SteveS · #7 Post by **SteveS** » Thu Nov 06, 2008 8:44 pm

The higher current/power ratings of the T4x series is needed to support the two USB 2.0 connections. The USB2.0 spec states that each connector can power up to 500 mA. Very few devices use anywhere near this much power, although a few external hard drives and scanners do.

Basically, the computer will work just fine with the smaller power supply, provided you are not using two of these power hungry USB devices. I am not sure what would happen if you current limit the power supply. The T41 supply might not be happy being fed under voltage.

#8 Post by **schen** » Thu Nov 06, 2008 9:07 pm

rkawakami wrote:I would have to assume that the T20-T22 systems having a 3.36A rating can be safely powered with the 3.36A (aka, 54 or 56 watt) power supplies regardless of whether or not they are plugged into a port replicator or docking station.

You might be right in saying that IBM shipped the early T2 systems with the 4.5A (72 watt) supplies as they were "current" inventory at that time.

If in doubt, do what I do: only use the 4.5A supplies with any of the 16V Thinkpads.

My experience with T Series ThinkPads being with the T20 through all 4 versions is that every one that I purchased for the institutions I worked for at that time came with 72w (4.5a) power supplies of the "dogbone" variety. Although, not as extensive, my experience with the contemporary A2x series was that they also were shipped with those adapters as well. Even the early X20s we bought were equipped with those. It wasn't until later that I started seeing the smaller "X" style adapters with those machines.

That's just my experience on this of course.

mpcook · #9 Post by **mpcook** » Fri Nov 07, 2008 6:58 am

My memory (which is admittedly not very good any longer) having purchased new T20, 21, and 23's is that the early T2*'s shipped with the 72 watt but the smaller 56 watt was offered as an accessory. I believe at the time, I ordered it so I would have a lighter one for travel and home, and larger one stayed in the office.

Mike

awolfe63 · #10 Post by **awolfe63** » Fri Nov 07, 2008 11:49 am

I've tried both. The T23 72W supply works fine (and appears to be identical to the T4x supply). The 56W supply works sometimes - it is flaky on my T42s. I wouldn't use it.

Will T21-23 power supply work with T41?

Will T21-23 power supply work with T41?

Who is online