Master battery backup. By John Ilsley. This article is for Master128 users,
and for one user who questioned Daniel
about the Master128 battery backup.
The official battery, doesn't last 5
minutes. It is also sometimes forgotten
that the Master128 has the capability
of charging its own battery.
The Master128 only draws power from the
battery during the times it is switched
off when the timer chip, date and
configuration settings are maintained.
For this it draws very little current,
but enough to send the batteries flat,
especially if the computer is not used
for a few days.
There is however a simple way to cut
buying your batteries by 1/8th or more.
It involves a very simple alteration to
your computer. Simply follow these
instructions.
Note: Neither 8BS, the editors or
myself can be held responsible for
anything that should go wrong should
you not follow these instructions
correctly. I suggest that you draw out
how the battery is at present in case
you wish to revert back to it or if you
find something goes wrong.
You will need the following tools:
Soldering iron, solder, a couple of
pieces of wire about two feet in all. I
suggest you get one foot of red and one
foot of black. 24swg will be fine.
Please note, if this battery is not
connected the correct way, it will
destroy your configuration settings and
if left in, will destroy the timer
chip. Therefore you MUST follow these
instructions carefully. This picture
will also be very helpful:
+
Note White -
diode end ] IN4004
diode
Don't use
Ni-Cads 120ohm
resistor
+
Battery
- -
I am willing to
+ make these up if
you can't But I
Batteries cannot accept
responsability if
- + you install them
badly or have the
^^^ wrong machine
Stiff wire
First, turn off your computer, remove
the plug, get your coat and go out and
buy three long life AA size 1.5v
batteries, Duracell are the best for
this, they have more Ummph!...
One Diode type IN4004
One 120 om 1/4 watt resistor.
(Brown Red Brown).
Save your configuration:
*SPOOL status
*STATUS
*SPOOL
As you may lose your configuration
settings
Now, remove the case, do this in the
normal way by removing the four fixing
screws from underneath the computer,
also removing any cartridges in it.
Now check that the leads go from the
battery to the left hand side of the
circuit board on the edge about half
way down with the positive wire (red)
being in the center and the earth
(black) being at either of the ends. If
they are, then to continue should be
ok.
If you have access to a test meter then
test for positive and negative or just
follow the battery terminals down.
Now you will have to be careful when
doing this project as if the batteries
get too hot and over heat they may
explode in your face showering you in
hot acid. I strongly suggest eye
protection for this. Sounds silly, but
better then losing your sight.
Take each battery and sand the top and
bottom down with sand paper. Then put a
spot of solder on the top and bottom of
each battery. Take two of the batteries
and join the positive (+) end of one to
the negative end (-) of the other. So
you end up with one on top of the
other. This can be done using wire or
by a quick solder job. If it ever gets
too hot, leave it for a while.
When you have done that, find a piece
of stiff wire, a leadout wire from a
resistor or a diode or similar will do.
Place a spot of solder on the ends, You
may have to clean them first, then
place it on the positive (+) end of the
two batteries. Then connect the
negative (-) end of the third battery
to the other end of the wire. Tape the
two batteries that are side by side
together.
Solder the 120ohm resistor to the
positive (+) end of the third battery,
take the diode and placing it with the
white end AWAY from the batteries,
solder it on to the other end of the
resistor.
Strip 2/3rds of a centimeter off the
end of the black wire, twist and flux
it with solder. Then solder it onto the
negative (-) end of the battery. That
is the end away from the diode. Strip
2/3rds cm from the end of the red wire,
solder it to the end of the diode.
If you have access to a testmeter,
chect that the voltage is about 4.5v DC
from the red and black wire. If not,
then something is wrong. Go through it
again.
If it is ok, make sure the computer is
off, insulate the resistor and diode
from contact with either the batteries
or the computer. Ensure that it won't
all fall to bits. I found a resin glue
works fine for this.
Place the three batteries into the left
hand side of the case down by the side
of the keyboard, they should just fit.
Strip the loose wire ends, flux them
and then touch the metal case of the
power unit with the tip of the
soldering iron so to earth it.
Now all you have to do is solder the
positive (+) wire from the battery to
the center of the three pins, then
the negative (-) wire to the pin
nearest the keyboard.
Make final checks, make sure the wires
are in the right place, no solder is on
the computer or circuit etc.. Then turn
the computer on. If your'e lucky you
will get the original settings you had.
If not you will get:
ACORN THIS IS NOT A LAUNGAGE.
If you get this, all you have to do now
is reconfigure.
If you get a wierd screen or nothing at
all, switch off and recheck everything
and try again. If you still don't get
anything, DO NOT CONTINUE. Replace the
battery as it was originally then try
and turn it on. If you need any help,
then give either Chris, Daniel or
myself a call.
John Ilsley 27N