>I usually do not charge the batteries with the notebook but with a
>better external charger, so I think replacing the batteries with NiMH
>1200 or 1700 mAh-types is possible (for around 1 Euro per cell
Err ... careful with that.
The "3/4" NiCd cells used in the batteries are about 5 Euro (10 DM)
www.reichelt.de ... and the battery includes a thermal shut-off sensor.
NiCds have a different behaviour after about 90% charge to NiMh, where
the charge current rises dramatically after 90% - and the sensor may turn
out to be oddly placed and react too slow. NiCds grow hot - NiMhs go low
resistance (before getting *really* hot). The U/I characteristics of both
differ quite a bit - and the charger circuit is already insuffient for
With using NiMh and inappropriate charging curve you may run into quite
a bit of real trouble ....
The N33 has a main power switch at the rear (above the large bus-connector)
- and one on the front. If both are "on" and the machine still don't come
up ... well ... then the notorious microfuse in the DC-DC converter is
most likely blown.
I have fixed several of these machines already ... the last one reached
me in a package ... :-)
The repair itself is not *that* difficult (about level 3 - on a scale
[dead easy] to 6 [almost impossible]) - but the disassembly of the
machine and finding the darned thing might take some time.
Try running it from the mains with the battery out - I have seen several
N33/N51s that appear dead until the battery is taken out. It may indeed
be the fuse problem, as Peter describes.
The N33 portable has some problems with the internal DC/DC converter.
It has two small cylindric fuses. If either one is blown the system
- run fine on batteries but not on AC and the battery is not charged
- or run fine on AC but not on battery.
To remove and replace these fuses the system needs to be fully disassembled
and the fuse(s) unsoldered. This is fairly tricky if you do it the first
time. I did it maybe several dozen times back then. The N33 had been part
of a portable solution for insurance sales people over here in Germany
(along with a portable printer installed in a suitcase) and the machines
returned to our repaircenter like boomerangs ... :-)
Instructions on replacing the fuse of an IBM N33SX notebook (8533-G15).
Please note that this should only be done if you feel confident in
a) precise soldering
b) takeing apart electronics and reassembling them without ruining
a) You have been able to find a replacement fuse (the one(s) we are
talking about can be seen when the notebook is opened without the need
of taking out the system board - they are two round black plastic fuses
about 6 mm in diameter right next to the power supply input (i.e. where
you plug in the power supply). The fuse that lets the notebook run on batteries
only, but not AC is the one closest to the housing of the notebook, rated
125V, 3,15A. I successfully replaced it with a Wichmann TR3 type fuse,
which seems to be the only similar one available around here. I don't know
the rating of the other one since I didn't replace that and the labelling
can't be read without desoldering it - maybe someone else knows.)
b) You have taken care against static electricity, a grounded wristband
would be best.
c) You have managed to open the housing of the notebook - I leave that
one to you. (If you can't take it apart don't read any further, you
might hurt yourself... ;-)
d) You have paper and pencil ready. You need to take notes of what
connectors you opened and where the screws and parts came from. Label
every screw that you take out - there's a big variety of them and if
you don't mark them it's going to be hard to put them back to where they
came from... Also, take note in what order the screw fixes the parts of
the notebook - sometimes the screw will hold a spring, a washer, a metal
shield, a metal carried and the PCB at the same time... (You might not
do recommendation d) if you are an experienced notebook technician but
I prefer to ;-)
Today's ASCII art - this is the notebook seen upside down with the cover
open. It is not an exact scale...
X means "Screw to be unscrewed" (numbered)
O means "Connector to be unplugged" (Multiple "O"s in a row/line mean
! means "look at the notes below"
RAM BANK |
| +----+ +-----------+O|
| | X5
| HDD |
| FUSES OO O|
| CONN |
| PCB | +-!---------------------+----+
| OO 7X|
How to do it:
Unplug connectors whenever possible. It's probably smart to unplug
connectors to the backup batteries first (the ones of the above
connectors that are two-wire black-and-red connectors - pull these
Screws 1,2,3 hold the HDD. Unplug the HDD cables too (be careful) and
take out the HDD - nice opportunity to upgrade it, too... ;-)
Screws 4,5,6,12 hold the system board, 5,6 hold the metal lineing of
Screw 7 hold the floppy disc connector PCB
Screw 8 screws the serial connector assembly to the housing - it's
between the PS/2-Conn and the BUS-Conn
Screws 9,11 hold the modem lining
Screw 10 holds the cover that is in front of the modem space
Screws 12,13 hold the modem connector PCB
Assembly is reverse of Disassembly. There is a "!" in the above drawing.
Take care when reassembling here: At the outer end of this metal there
are two metal noses that hold the system board in place - the board
in between the two noses - if you misassemble here, it might damage
That should do the trick. Please note that I do not take any responsibility
for bad repair attempts. I do not guarantee that the above information
Have fun repairing your notebook, Norman
PS: If anyone has the possibly and is interested in putting these information
on a website, I'd photos too... ;-) PPS: All in all I wish IBM would build
an up to date notebook exactly like the N33SX - small, lightweigth and
powerful, nice keyboard, nice finish - the Thinkpads et al. are good, but...
* Norman Weiss * http://www.normanweiss.de *
* newsreply(at)normanweiss.de *
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