Will these AC adapter work well with a T42?

[Edward Mendelson]

Happy New Year to all, and here's a question for the new year:

I have two spare ThinkPad AC adapters, both rated on the back as having Input:100-240V~1.5A-0.9A, Output 16V--4.5A.

Having long since forgotten my high school physics, here's my question: Will these work correctly with a T42 that came with an AC adapter with the same ratings EXCEPT that the input amperage is listed as 1.9A.

Any information gratefully received.

Edward Mendelson

[Leon]

search old threads for details, but the short answer is......

some have used them and report no short term problems, IBM recommends against, stating that the circuitry in the T42 Mobo is "tuned" for the Amp. rating of the newer adapters.

My personal recommendation is not to chance an expensive machine for an item that can be picked up very cheaply on ebay....... YMMV

[Edward Mendelson]

That was very helpful - thanks. As you suggested I did look up the earlier thread here:

http://forum.thinkpads.com/viewtopic.php?t=2180

In the last entry, Leon says that the difference in input between the old and new adapters makes no difference, specifically: "yes, input variance like that makes no difference (input is what it is).. they are 100% compatible"

So, unless an electrical engineer or someone equally well-informed jumps in and says that Leon (who identifies himself as an EE) is wrong, can I assume that what Leon says is correct? In other words, the input TO the adapter doesn't matter, what matters is the output FROM the adapter to the ThinkPad, so that if the OUTPUT specs of another adapter match the OUTPUT specs of the shipped-with-the-T42 adapter, then the two are completely compatible?

Thanks again to all,

Edward Mendelson

[JHEM]

Happy New Year Ed!

That was very helpful - thanks. As you suggested I did look up the earlier thread here:

Basically, input variances are moot but you MUST match the output voltage as closely as possible on differing power bricks. Tip polarity must, of course, match also.

That said, amperage is a different matter in that it's best to have a power brick match or be capable of GREATER output than to use a brick with lesser output.

E.g., the laptop will only draw as many amps as it needs to operate, charge the battery and operate accessories REGARDLESS of a power brick having the ability to provide more amps. So if the brick is capable of providing 2 amps but the laptop only needs 1 amp, the laptop will still only draw what it needs.

Conversely, if you have a 2 amp rated laptop and a 1 amp rated brick you may see the laptop not be able to run at full speed, the battery will take longer to charge, etc., etc., to the point that the laptop's internal DC/DC card and charging circuitry can be damaged. You will also note that the brick will become very hot as it's in this overload condition, to the point where a fire or simple failure is not impossible.

I'm not an EE, but I get paid to play one frequently!

Regards,

James

[Edward Mendelson]

James,

Helpful and informative as always!

Just to confirm: Does this mean that the various AC adapters that I described at the top of this thread - all with identical specifications EXCEPT for the adapter's INPUT amperage - are fully compatible (provided that the tip polarity is the same, which I'll check again)?

Again, to clarify: the two older adapters that I'm asking about both have exactly the same OUTPUT specifications (16 volts, 4.5 amps) as the adapter that came with the T42. The only thing that differs is the INPUT amperage, which is lower on the older adapters. You say that essentially input amperages are moot - so that means that I can actually USE these adapters without worrying about frying or exploding my shiny new T42??

Because that T42 is so nice have, I'm hoping to have either a definitive and explicit, "Yes, use those adapters without worrying for a moment" or an equally explicit "Um, er, no, you're STILL not getting the point after all this time, and I wonder how many times I'll need to tell you that you're risking your T42 by using those adapters." One or the other would be very reassuring...

Thanks again, as ever,

Edward

[jdhurst]

Unless the adapter designer pops in here and answers your question, you may not get a definitive answer.

All of the adapters for my A22e, T23, T30 and T41 all produce 4.5A at 16V and are the standard (16x4.5=) 72 watt adapter. They are all interchangeable without harm to any of the units.

Now the adapter for my T23 has an input of 1.4A to 0.7A. The adapter for my T41 has an input of 1.4A to 0.7A. The second, IBM, vendor-certified as replacement adpater for my T41 has an input of 1.5A to 0.9A. The last adapter is physically smaller than the first two. It is shorter by 0.5 inch or so, and therefore will have different internal circuitry and quite likely different efficiency levels.

I dont have a T42 and can't say about it. But if you look on an oscilloscope (I did) the newer, smaller adapter has higher frequency components than the older one. It may switch faster internally to produce the same power in a smaller package. Who knows if this is the "tuning" referenced in an earlier post.

I would heed IBM's advice on adapaters, although it is sad if they have two different 72 watt adapters with the same plug that are not interchangeable. You might wish to ask your vendor.
... JD Hurst

[Leon]

I am the same "Leon" above and in the other post. Actually, when I first read your original post, I misread the difference in the ones you were comparing to be output rather than input. My advice in the prior post stands... you may use them with no problem. I use them daily. It is the output that must be matched.

p.s. "Yes, use those adapters without worrying for a moment"

[Edward Mendelson]

Terrific, Leon - thank you! (And I'm sorry I didn't notice that you were the same Leon in both threads.)

[Leon]

no problem.... enjoy your shiny new T42, and visit/participate in our forum often!

[JHEM]

p.s. "Yes, use those adapters without worrying for a moment"

What Leon said Ed! Sorry I wasn't more explicit the first time.

Regards,

James

[w0qj]

i have a very old IBM Thinkpad 560 AC Adapter that i use for my T40 & T42 and it still works--it's maximum rated Amperage is slightly lower than "required" for T40/T42 but it still works apparently perfectly.

hope this helps.

[Leon]

if you are talking ouput Amps., it will work, but is not recomended

[w0qj]

Hi Edward,

Just an update for your reference,

Your old power adapter may work, but if you consistently over use it, it may fail prematurely.

my compter is:
T42s 2373-K5H
1 GB RAM
7K60 Hitachi Travelstar HDD


This past 6 mths, I've been using my old IBM Thinkpad 560's power adapter (35W, 2.2A, Part No. 12J1443) with no apparent ill effect on above computer for occasional use (secondary power supply for limited use at home).
Check emails, type up misc. office document, excel use, etc.
Just light use...


BUT just last week, i used my T42s very heavily for an entire day (burn my CD's into MP3, while doing MP3 edits of my tapes at the same time (all personal materials), and charging my 6-cell battery at the same time.

At the end of the day, the old nearly failed (overheat, started to have a burning smell--i disconnected it immediatedly), possibly due to power over-draw (RAM, CPU, HDD, CD-ROM, battery recharging all in use constantly for while day).

This old Thinkpad 560's power adapter (35W, 2.2A, Part No. 12J1443) still works--but only my wife's T40 with occasional use now.
It simply don't work on my T42s anymore (maybe the overheating damaged it's power output permanently).

Just for everyone's reference, for what it's worth...

[Edward Mendelson]

Thanks for the update! After reading the thread here, I've decided to use ONLY adapters that have the same OUTPUT as the supplied TP42 power brick, and have had no problems at all. Your experience confirms Leon's warnings earlier in the thread.

[JHEM]

Your experience confirms Leon's warnings earlier in the thread.

Leon, always Leon!

What am I Ed, chopped liver?

Regards,

James

(Ducking and running!)

[mdarnton]

I get the idea that the object here is to save money, so here's a tip. For some strange reason there are always lots of IBM AC adapters on Ebay, cheap. They're always "like new" which implies used, I guess. I wonder why there's a constant flow of them? Right now there are several compatible ones for about $17. That's where I got my extra one for work (one work, one home), and it was a perfect match for the one that came with the computer. Why mess with making the wrong thing work when the right one is only $17? :-)

[Edward Mendelson]

<EDIT> Leon and James...!!</EDIT> with thank to both!!

[Leon]

LEON SAYS... the ebay ones are great.. I have SIX of them (keep power ready in all my working locations...... (JHEM probably has one or two himself )

[JHEM]

LEON SAYS... the ebay ones are great.. I have SIX of them (keep power ready in all my working locations...... (JHEM probably has one or two himself )

James has many as James was astute enough to grab a bunch of A/T/X port replicators from a seller on eBay for only $7.99 and each came WITH a 72W brick!

James is also famously cheap!

Regards,

James the Frugal

[Leon]

Yeah, but think of all the environmental problems that will be caused by those 6 obsolete replicators.......NJ landfill, here they come....

I know u feel guilty now......

Leon The Environmentalist

[gazingwa]

or, paperweights, door stops, take the innerds out and make it a lamp rod, see they are still usefull.

David, the recycle guy