Powering a T4400 series notebook

I have been asked numerous times how to supply power to a Toshiba T4400 series notebook. These notebooks are appearing everywhere from eBay to garage sales and sometimes come without the matching AC Adaptor. Well, the good news is that the T4400 runs fine without the proper AC Adapter if you forget about charging the battery. Since most NiCd batteries produced for the T4400 are beyond their useful life anyway (the T4400 was produced around 1991/1992) running it from mains almost always is the only way kicking some life out of it.

The original adapter (brick sized) comes as model PA2408U. It supplies 21 Volts at 1.9 Amps. There is a problem though. At the time, Toshiba decided (I reckon because of lack of space within the actual notebook) to integrate some of the charger electronics (i.e. the circuitry that supplies the proper current to the battery) within the external AC adapter.

So, where the PA2408U supplies power to the T4400 notebook, it also supplies current (at 21 Volts) from a separate pin to the T4400 and the T4400 supplies a signal to the PA2408U telling it how much current to supply. This circuitry is very hard to duplicate since there exist no schematics of the PA2408U and disassembling it is only possible by actually ruining it. (I do own the schematics of a Desk Station IV though which can also charge the battery, so anyone brave enough to build their own charge circuit can contact me.)

The power connector to the T4400 is as follows:

/------------\
| o  o  o  o |
--------------
  4  3  2  1

Pin 3 has a notch.

Pin layout:		1	DC 21V, 1.9A
			2	DC 21V, 1.9A (max.) charge current
			3	Common (-)
			4	R.C.

I have been told a 3 1/2" floppy disk drive power connector can be made to fit.

So to run the T4400 on mains you need to get a well regulated 21V DC power supply able to supply around 2 Amps and connect it to pins 1 (+) and 3 (-).

Pin 4 (R.C.) is the signal from the T4400 to the PA2408U that tells it how much current to supply (at 21 Volts) on pin 2. The signal on pin 4 comes straight from the power supply board's CPU within the T4400.

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