I don't plan on doing this, but have any of you out there tried this interesting modification? http://www.stud.ee.ethz.ch/~blutz/TI89Spec/TIAccelerate.html Is the address for the site I found this modification on.Title: Accelerate TI-89
© by: Boris Lutz (blutz@stud.ee.ethz.ch)
I replaced the capacitor C10 (47pF)
which is responsible for the speed with a smaller one
(10pF). This makes the TI up
to The
accelerated version of the TI-89 needs a little bit more power of a
regular TI-89.
The best method to be able to change the speed is to use a
variable capacitor. You would be able to change
the speed continuously and play Assembler games at a reasonable
speed.
I accept no responsibility for this procedure and any damage that it
might cause, but if you follow my guidelines it works perfectly!
Don't use a capacitor with a capacitance below 20pF, this won't be
stable!
The procedure described on this page is for the TI-89, the procedure
for the TI-81, TI-82, TI-83, TI-85, TI-86 and TI-92 you can find
here.
First make a backup then remove all batteries. There are seven
screws which need to be removed. Two right below the battery cover, 2
above it, two at the top and one that holds in the backup battery.
Once the screws are removed, you have to take off the bottom part of
the case.
To do this, first use the small regular screwdriver to pop the bottom
corner up. Then take the battery cover and slide it along the side of
the calculator. It will force the sides to pop open.
Enter-Key F-Keys
________________________________________
|
|------>---->---->---->---->---->---->---
| \ /
|______\___________________________/_____
\ /
\ /
Open here slide until here (on both sides)
After opening the TI, you'll see a silver shield covering the TI's
circuit board. Remove the two small screws at the bottom of the
shield.
C10 is on the right side of U5 if the
the display is at the top.
+-----------------------------------+
| | C
This plan shows | | 1
an enlargement | | 0
of the part of | |
the TI-89 board | | R
around C10. | | 1
| U5 | 2
| |
| | R
| | 1
| | 1
| |
| | C
| | 9
+-----------------------------------+
First desolder C10 from the board. Be careful: Do not
overheat any part!! Now you put the
20pF capacitor where the old C10 used
to be.
Some TIs might work with a capacitor below 20pF, however this won't
work on all TI-89s and is surely not as stable as a 20pF.
That's it, put back the shield (be sure, that it's position is
properly adjusted), fasten the black plastic cover with the screws
and put back the batteries (the four AAA batteries and the backup
battery).
Just removing C10 or implementing a switch, like described
on my TI-85 acceleration page is not recommended! Why: Just
removing (without putting in a new capacitor) the capacitor will
cause the TI-89 to freeze. (you have to reset it) Implementing a
switch is more difficult with the 20pf capacitor, you can't connect
the 20pf and the old capacitor in series (you would have a capacity
of about 14pf and that's not enough, this would cause some
errors)
To use a switch you would have to use a 35pF capacitor
connected in series with the original capacitor and the switch over
the 35pF capacitor (when the switch is closed the 35pF capacitor is
short circuited).
A second possibility is to use a switch which connects the 20pF capacitor directly to the board and in the other position it connects the original one to the board. This will be a bit slower than the first method.
The best possibility is to use a variable capacitor with a range from about 18 (not lower) to 50pf. With a variable capacitor you would be able to adjust the speed continuously.
You must have some experience in soldering, to do this!
This is the way how I do it: Take a small
screwdriver (like the one to open the calculator). Heat up one side
of C10 (not longer than one second), quickly change to the other side
and heat it up, change back and so on while you are carefully trying
to push away C10 with the screwdriver. DON'T push too hard
and DON'T heat up C10 too long!
If you push too hard you might destroy the solder pads!
However there is a way to connect the capacitor even if the pads are
destroyed but it's much more difficult.
The original capacitor is a SMD (surface mounted device) they are
rather small and more difficult to get, but you can use any 20pF
ceramic capacitor, which is small enough to fit in. If you get a
regular ceramic capacitor it should look like the picture below (not
that big, it should be about 1/6 x 1/6 inch large).
Note: It is possible that your capacitor looks different, the most
important thing is that it is labled 20pF!
To solder it directly to the board, proceed like this (see ASCII pictures below): Cut the two wires from the capacitor after about 1/4 of an inch and bend them about 1/8 of an inch away from the capacitor (but be careful not to damage the capacitor). Now you can solder the two ends to the board.
(top view)
+---+
0----| |
| |
0----| |
+---+
(side view)
+---+
+---| |
| +---+
|
The best possibility to adjust the speed of the TI-89 is to use a
variable capacitor with a range of
about 18 (not lower!) to 50pf. With a variable capacitor you would be
able to adjust the speed continuously.
To do this you need two about one inch long wires, the variable
capacitor and an electric drill. First solder one end of each wire to
one pad where C10 used to be (after removing C10, you won't need C10
anymore) it really doesn't matter which terminals you use.
Now solder the variable capacitor to the other end of the wires. If
the variable capacitor has three connections, connection one and two
are connected together. Solder one wire to connection one or two and
the other to connection three. If your capacitor has just two
connections it doesn't matter which terminals you use.
Make sure that all your wires are as short as possible otherwise your
calculator won't be as fast as it could be. I found it easiest to run
the wires around U5 and then tape them down using lack electrical
tape. Just use small pieces of tape. Try not to cover any components
on the board. Especially not the connections of the backup
battery!
Take off the back of the TI and remove all batteries, make a hole
next to the backup battery like on the picture below, just large
enough to hold the variable capacitor.
Place the variable capacitor in the hole and make sure that you
are still able to close the battery cover, maybe you have to shave it
a bit or make a hole in the cover too. I used a hot glue gun to
secure the variable capacitor, but just about any type of glue should
work. Put the glue only to the bottom of the variable capacitor on
the inner side of the case. Make sure that you don't put any glue at
the top of the variable capacitor so that you're still able to adjust
it.
The last thing I did was to put black tape on the silver shield where
the variable capacitor would touch when the case is put back together
(don't cover any parts of the board especially not the parts where
the connectors of the backup battery touch it). I also cut a small
square notch out of the side of the shield for the two wires to bend
up from the board to the variable capacitor.
The variable capacitor can be adjusted with a small screwdriver. (the
capacitance is adjusted continuously by moving the plates of the
capacitor) You have to try out which position is the fast and which
is slow. In general you can adjust the speed from 80% to 200% of the
original speed.
Note: When your calculator turns on with a few rows of black lines after you have accelerated it, you have to completely reset the calculator. Click here to see how
If you have any questions please first have a look at the SpeedUp FAQs and Trouble shooting if your question(s) are not answered there, feel free to send me an e-mail
Boris Lutz
blutz@stud.ee.ethz.ch
http://www.stud.ee.ethz.ch/~blutz/
You can share this plan with other TI users as long as you don't
change it and include my e-mail address and home page URL.
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