power supplies

[Dickyboy]

I bought a "genuine" IBM power supply from ebay, amazingly cheap, lasted about 4 hours. Not sure how you verify the genuine, the label looked good so don't want to go there again.
For the techies:- I have an 18volt power supply, will that frazzle a T21? could I put in a 1 ohm shunt to drop the volts , or is that not required. Would a 15 volt power supply suffice or will that frazzle the T21?
Sorry for the basic questions but I don't want to lose a trusted friend to a fireball.

[ZAGNUT]

inside the machine there is a switching regulator that really shouldn't care about the input voltage as long as it's not too far off. i suspect that IBM chose 16 volts for the power supply as this would probably allow the regulator to run as efficiently as possible while generating the least amount of heat.

i plug my T30 into my car's lighter socket all the time and it runs and charges just fine. this is about 13 volts with the engine off and a bit more when it's running. i haven't tried a higher voltage than 16 but i'm sure it would handle it just fine. a friend uses an IBM 16 volt supply for his fujitsu after the original 14 volt supply died. things like the caps inside the machine should be rated for at least 25 volts because the next lower rating is 16 volts and it would be considered bad engineering to not allow a good safety margin.

of course someone will come along and say you'll fry your machine with even 16.1 volts.....



dave

[jdhurst]

The power adapter for the T2x is the "standard" 16V 4.5A 72-watt supply. I know it is for the T23 through T4x and I assume so for the T21.

You can probably purchase a known good adapter here (Marketplace). I purchased extra 72 watt and 90 watt adapters here and have no difficulty with them.

I strongly suggest not using some makeshift adapter. ... JDH

[rkawakami]

Welcome to thinkpads.com!

Sometimes the knock-offs (i.e., fakes) are so good that they could be mistaken for the real thing. Other times, it's fairly obvious that you have a non-OEM supply - it will say "For IBM..." or "Replacement for IBM" somewhere on the label.

As far as the voltage input to the system goes, most every time I measure an IBM 72 watt AC adapter, the output voltage is around 16.6V. Putting 18V into the laptop may or may not smoke your system. Especially if you try something un-regulated like your 1 ohm load. Going the other way, 15V may not be enough to properly maintain the internal supplies and/or charge a battery correctly.

You would be better off using a proper 16V 4.5A supply that's designed for the Thinkpad. Many are available on eBay or here in the Marketplace. Was there no warranty with the supply you purchased?

[gn2]

Virtually no experience here, but I bought a "no name" supply from ebay, it put out 16.3VDC according to my DMM, it wouldn't start my T30. Tried a genuine IBM supply from same said ebay, it put out 16VDC on the button, and the T30 sprang to life without any hesitation...
I don't know if it was the voltage difference or some other factor, since the T30 was yet ANOTHER ebay purchase, so who knows if it has any other issues, etc.
But, I sent the no name ps back, and the overvoltage was reason enough for them to accept it for RMA...

[sparta.rising]

T20 says (on the bottom label) 16V 3.36A =53.76W but 72W works fine (and tawbook lists it shipping with 72W)
T23 says 16V 4.5A = 72W

Sorry don't have a T21 handy, but all laptops that I've come across have listed the input voltage on the bottom. My Armada M300 lists 18.5V 2.25A but runs fine on a standard 72W Thinkpad adapter.