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NC100 FUSE REPLACEMENT.
(Updated 20th September 2006)
 
Own a dead Amstrad NC100 Notepad? --- connected the wrong power supply to it? --- then the fault could be a blown fuse, try everything else first as recommended in your manual, then if no luck follow the instructions as kindly offered below by Rod Brown 'Who took up computing when they still used valves'. This is not for the non-technically minded --- but it works most times.
  1. Flip the NC100 so it face down, with the serial port pointing away from you, remove the main batteries, and leave the cover off. Remove the backup battery and leave the cover off. (now you know why you will loose all the data)
  2. Remove the screw from the case by backup battery, remove the screw from inside main battery compartment. Working further down the back of the case, now remove the screw from letter box shaped cover, centre left of back (32 pin firmware chip inside) remove the screw to left of firmware cover . Remove one last screw at centre right of back.
  3. Putting all the lose bits well out of the way, stand the NC100 up with back towards you, serial port to left and printer port to right, and start freeing the plastic clip around battery compartment, (where the two halves of the case join).
  4. Continue to free any clips down either side of the case from top to bottom and as you do lower the back of the Nc100 down to the table. You will be looking at the NC100 face up, but with the display towards you and the keyboard away from you. The last clips are along the thin edge of the base of the keyboard.
  5. You will now need to carefully lift the loose cover slightly till you can see a small white plastic plug (speaker) and disconnect it, this will allow the cover to lift further, which shows the printed strip lines to the LCD display. "CAREFULLY DISCONNECT BY PULLING SIDEWAYS WITH EXTREME CARE" . The top cover can now be removed (beware the speaker can fall out of its slot, at this point). Put the top assembly VERY carefully in a safe place.
  6. Time to turn the machine round so the keyboard is towards you. You can now see the two strip lines to the keyboard. again "carefully remove these" by pulling directly upwards, the keyboard can now be taken away by lifting it up at the upper edge and pivoting it out and away from the bottom of the case.
  7. Laid out before you is the surface mount, printed board which is the NC100, its very neat but the part you want is on the underside of the board, of course , (where else would they have put the only part you may want to repair). The memory expansion port is connected by a rectangular plastic molding to the board, this just pulls away as you lift the board. Now remove the four chrome screws holding the board to the metal screening, two either side of the serial and printer ports, a small metal shield will be freed which you will need to put to one side.
  8. O.K. -- its time to take the board out and turn it over, but it will be retained by the two main battery connectors which fit in grooves in the battery compartment. Gently slide these out and your board should be free to remove. Please ensure any metal and plastic plates stay in place in the lower case, remove the board and turn it over.
  9. Surgery time now, but first identify the fuse. its marked as F301 and rated at .8amp (800mA), this can be either a cylinder or a rectangle, but it will always be located in the top left hand corner of the board, to the right of C399 and above R396. (See the picture below of that corner of the board, which if you can view it, also shows a single stand of wire passing over the top of the fuse.) I have never been able to find a source of these fuses, hence the wire.
    A note from John King:- You perfectionists could always purchase a 1.25 inch 800mA fuse and very carefully remove and use the wire from inside of it.
  10. Fire up the soldering iron and make a short link from one side of the fuse to the other, I use a single strand, of multi core wire, to make the link. And at my age, I also use a magnifying glass.
  11. Time to admire your handy work, and take a break, because the next step is to put it all back together, but you will need to be very careful when replacing the strip lines. So after a rest to steady the hands, replace the board back into the case, by positioning the battery connectors back into the battery compartment, not forgetting the rectangular plastic molding. (oh yes, I did). replace the metal plate and the chrome screws holding this in place.
  12. Replace the keyboard assembly and very carefully connect the keyboard strip lines. Reconnect the LCD strip lines and the speaker plug. Turn the case over and starting at the bottom of the keyboard clip the case back together by pressing firmly till they click home. Flip the case over and pop the original screws back into their original locations. Place backup battery and main batteries back in the case and replace their covers. cross your fingers and then press the power button.(whew !)
NC100 fuse

NC100 Variant.

A recent encounter with a dead NC100 has revealed that there are at least two variations of this machine and the following will highlight the differences between this and the normally found type -- now I know why comments have been made that the above is incorrect!. Dismantling is as above but the hunt for the normal fuse block (as pictured above) will be fruitless. The fuse, as illustrated below, will be found on the top of the board (see figure 1) close to the power socket. It's removal is not a necessity but in my view it makes life easy. The fuse (figure 2) is a special and I doubt if still available (T500mA indicates a 500mA Anti-Surge fuse). As a replacement I opted for a length of 800mA fuse wire obtained from a standard 1.25 inch fuse (as recommended by me above). The wire was passed through a short length of sleeving -- I used orange sleeving but any colour will do! (see figure 3) and soldered on the underneath of the board using the two holes left vacant by the removal of the original fuse. The machine was re-assembled and fully tested -- yes it worked fine. It is now clear why owners of this variation would have been at a loss, when following the first set of instructions.

Fig: 1.

Fig: 2.
Fig: 3.

Power Supply.

For those of you wanting to find the correct type of power supply for your NC100 you will need to look for one with the following specifications:- 6 volts DC at 300mA (higher than 300mA is fine) fitted with a 2.1mm DC connector where the negative ( - ) side is connected to the centre of the plug.
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