How To Test 12 Volt Power Supply?

[kc27]

I have an IBM #10K0151 72 Watt Auto adaptor for my Thinkpad T30.

Even with the laptop plugged into the adaptor, (and driving at highway speeds) the Thinkpad's battery was drained. The laptop doesn't have this problem when plugged into the AC adaptor. It seems to me the DC adaptor has gone bad. Is there anything else I might be overlooking or should test to verify that this is the case?

If it does turn out the adaptor is shot, does anyone have any recommendations on a good unit?

Thanks in advance for any help on this.

[rkawakami]

At least four things you can do:

- verify that the car's cigarette lighter is operational; the fuse could be burned out.
- when the laptop is connected to the DC (auto) adapter, the laptop's charging indicator (assuming Windows here) should indicate it's being "line" powered.
- see if there is a fuse inside the adapter's cigarette lighter plug; typically it is accessible by unscrewing the metal tip of the plug. Check it with an ohmmeter for zero ohms.
- assuming that the fuse is present and good, plug the adapter in and measure the voltage at end of the DC plug - it should read around 16VDC.

[kc27]

I got around to measuring the adapter's output, it's only putting out 13.6 volts. I haven't even used it that much. I'm surprised it went bad.

Do aftermarket units exist that are acceptable replacements vs buying another IBM model?

[rkawakami]

Yes, there are aftermarket DC-DC adapters available but I've only used genuine IBM ones. As long as they can supply the 16VDC at 4.5 amps, have the correct polarity at the tip (center positive) and is the correct diameter (~5.5mm OD/~2.6mm ID), then it should work.