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Battery Pack 7.2V, 1700mAH(Ni-Cd)/cell, 6 cell/pack
IBM PS/2 External Battery Extender for Model N33 SX ???
Note: A quick charger is needed to charge the battery extender.
>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 = 6
Euro).
Peter replies:
Err ... careful with that. The "3/4" NiCd cells
used in the batteries are about 5 Euro (10 DM) at
www.reichelt.de ... and the battery [pack] includes a
thermal shut-off sensor. NiCds have a different behavior
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 insufficient for
charging NiCd.
With using NiMh and inappropriate charging curve you
may run into quite a bit of real trouble ....
Peter said:
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 from 0 [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 cylindrical fuses. If either one is
blown the system either
- 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 repair center 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) taking apart electronics and reassembling them
without ruining them.
Prerequisites:
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 Wickmann 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.)
Note: According to the German
"N33SX" Wiki page:
"Complemental description: The fuse that safeguards the
mains operation and the charging of the batteries is a
Wickmann TR3 125V, 3.15A and the one for battery
operation is a Wickmann TR3 125V, 1.25A "
Littelfuse 303 Series - Micro/TR3 Fuses
(online) (local copy)
Look for the 303 1315 nnnn
But we have "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."
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...
Note:
X means "Screw to be unscrewed" (numbered)
O means "Connector to be unplugged" (Multiple "O"s in a
row/line mean a
longer connector...)
! means "look at the notes below"
+-------+--------------------+----------------------------------+
| 4X| RAM BANK | |
| +----+--------------------+ |
| |BIOS| X3 | BATTERY OO |
| +----+ +-----------+O| |
| | |O| |
| O | |O| |
| | |O+----------------------------------+
| O | | X5 X6 |
| O | | |
| O | HDD | +-------+
| O | | | |
| O O| | | |
| OO O| | | FLOPPY|
| FUSES OO O| | | CONN |
| OOOO2X+-----------+X1 | PCB |
+-!---------------------+----+ | |
| | X12| | |
|X11 |MDM O | |
| MODEM |CONNO | |
X10 X9 | X13| | OO 7X|
+-----------------------+----+--X8----------------------+-------+
How to do it:
Unplug connectors whenever possible. It's probably smart
to unplug the connectors to the backup batteries first
(the ones of the above connectors that are two-wire
black-and-red connectors - pull these first...)
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 lining of the battery compartment
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 goes in
between the two noses - if you mis-assemble here, it
might damage your system board.
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 is correct.
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,
lightweight and powerful, nice keyboard, nice finish -
the Thinkpads et al. are good, but...
-- Norman Weiss
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