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How to upgrade your 2400 modem into a 9600 baud

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How to upgrade your 24oo modem into a 96oo baud.  (US Robotics compatible
of course)
                                Written By
                   Death Bringer (CPT/Info-Net/IRA)


Be sure to turn off your modem before you begin.

First of all, you need to go to your nearby electronics store, don't try
to go to Radio Shack, their parts have their own model numbers and you'll
have a hell of a time getting the parts you need.  This upgrading of your
modem will not work on old hayes modems, but they will work on any clone
maker of modems (everex, practical peripherals, anchor, ati, intel, etc.)
It will only work with modems with the Intel Chipset.

This technique widens the band width by using a different chip that is
similiar to the chip already in your modem.

Parts Needed:
16550 UART
L4313545  IC
SC11020CN IC
L8730183  IC

First of all, check to see if your biggest chips are soldered or socketed.
if they are soldered, you'll have to de-solder the chips before you begin.
After you get that done, replace the 8250 UART with the 16550 UART. (16550
UARTs are required for 9600+ speeds).  The other 1 or 2 chip(s) need(s)
to replaced with INTEL L4313545 instead of the chip that is already there.
If your modem has another socket or more, than you are in luck, you can
purchase a chip from US Robotics, and make your modem faster than 9600.
If you don't have the socket, than you can only go 9600.  I'll get the
chip number to you in the next edition and explain how and where to
install it.  I am working on a way for the people (like me) that do not have
the extra socket in their modem to speed up the rates.  I am working on a way
to piggy back the chip.  I'll get back to you.  There should be a 22 pin
chip on your modem also with a model number of SC11005CN or some where close
to it.  Replace it with the SC11020CN.  Also, replace the L8630173 with the
L8730183 chip.  If you have any suggestions or questions, you can locate me 
through Compuserve USER ID 74702,97524

*****OPTIONAL, LAP-M Error correction*****

Adding error correction is rather simple.  For this these parts are

Potentiometer. This is a 5k audio taper variable resistor.

Capacitor. Any non-polarized 1.0 to 1.5 uf cap should do.

100 ohm resistor - quarter or half watt.


Solder, soldering iron, etc.

Solder one end of the capacitor to PIN 1 of the phone line input jack
|                   \ line in         ::
|                   \ phone in        ::
|-----------|||||||||            pin 1^

If your modem is external, the diagram looks like this.

|                 /|
|                 ||RS-232 port
|                 \|                  ::
|                |-|line in           ::
|                |-|             pin 1^
|                |-|phone in
|                |-|
This should be on the back of the modem.
Pin one should the farthest on the bottom left.

Solder the other end of the capacitor to the center lug of the potentiometer
(there are three lugs on this critter). Solder one end of the resistor to the
PIN 4 of the line input jack. Solder the other end of the resistor
to either one of the remaining outside lugs of the potentiometer. Doesn't
matter which one.


Bill McCauley & Dark Spyre/Dr. Brains/Ryan Schwartz/Lamer/Loser

First, a personal recomendation. _THIS WORKS!!!_  I have been plagued with
2400 baud for some time. I hate waiting for the transfer to finish so that
i can use the phone.  Threw the gismo together in about 10 or 15 minutes,
took another five to adjust the pot for best results on my worst
conection, and guess what? No more slow connections!


Have Fun!

I am working on cheap ways to install V.32/V.42bis on your modified modem

*************************Updated, 6/16/91********************************

Installing V.42bis:

1) You will need to purchase a 27C512 ROM chip.
2) You will need to purchase a Sony CXK58257P-12L (or equivalent) Ram chip.
3) Install the Rom in the Supervisor (SUP) socket.
4) Install the Ram in the Ram socket.
5) Make up two 3 pin jumpers for P9 and P10 with pins 1 and 2 jumpered
on one and pins 2 and 3 jumpered on the other.  Connect the vacant pin 1
on the one to the vacant pin 3 on the other with a jumper wire.
6) Remove the jumpers on P9 and P10.
7) Install the jumper with pins 1 and 2 connected together on P9.
8) Connect the jumper with pins 2 and 3 connected together on P10.

DeathBringer '91