MFJ MFJ-2400 User Manual
MFJ-2400 Instruction Manual
Thank you for p urchasing the MFJ-2400 TNC modem b oard. The MFJ2400 can be installed in the MFJ-1270, MFJ-1270B, MFJ1274 and
the MFJ-1278. With the MFJ-2400 installed in your TNC or Multimode controller, you can operate packet in three speeds - 30 0,
1200 and 2400 baud. The 2400 operation does not require
modi f ication to your radio and it uses the current radio port(s)
built into the MFJ TNCs or the M FJ-1278 multi-mode co ntroller.
The MFJ-2400 uses the EXAR XR-2123 PSK Modem IC. It is
configured to operate in the CCITT standard V.26/201 modem 2400
bps. The mo dem is compatible with other 2400 modems which employ
the same EX AR I C .
NOTE: Installation of the MFJ-2400 modem board in other TNC-2
and multi-mode controllers has not been tested. MFJ does not
guaranty the compatability of this 2400 modem board with T NC- 2
an d multi-mode of other manufactures.
TOOLS NEEDED
•
Controlled heat soldering pencil or small tip 3 5 to 65
watt soldering iron
•
Ros in core solder.
•
Med ium tip Philips head screw-driver.
•
Small diagonal cutters.
•
Needle-nose pliers
Be sure the work surface is clear and that all parts and
components are accounted for. Locate the illustrations that
pertain to the controller in which you wish to install your MF J-
2400.
If an "X-ACTO" cutting tool is used to cut the traces on the
circuit board at
use extreme caution to prevent personal
J4,
injury.
I. INSTALLATION FOR M FJ-1270, MFJ-1270B and MFJ-1274
A few minutes is all it takes to add the MFJ-2400 Modem to your
existing MFJ-1270, MFJ-1270B and MFJ-1274 TNCs. The addition of
the 2400 BPS feature should not require any internal
modification to your transceiver.
Remove the four screws holding the top cover on the TNC. Remove
the cover and set it aside. Remove the two screws holding the
front face plate, and set aside . Remove the four screws which
hold the main PC board to the bottom plate.
MFJ-2400 Instruction Manual
Carefully lift the main PC board from the bottom plate and place
on a towel or soft surface, COMPONENT SIDE DOWN. Be sure no
damage is caused to the components on the top side of the PC
board as you perform the 20 pin header installation.
A . IN STA LLA TION OF THE 20 PIN HEADER: Refer to FIGURE 1
Insta llation of the MFJ-2400 Modem is made to the MFJ-1270, MFJ1270B MFJ-1274, by carefully cutting three traces at the modem
header, between pins 11, and 12, between pins 13, and 14, and
between pins 17 and 18. CUT ONLY THE traces listed here. A good
magnifyin g glass is helpful while performing these cuts.
Make note of the number progression and location of the pins.
Keep in mind th e n umber progression a ppears to be reversed when
t he PCB is upsi d e down.
The drawing at FIGURE 1 will help you locate the header traces
to cut. Use "solder-wick" or a solder vacuum device to remove
any solder which may be covering any of the 20 pin header
holes. Cut the traces between the three (3) points shown in the
illustration.
20 0000000000 2
Bottom of PC board x XX Cut at X" 19 0000000000
1
front
For a more detailed drawing, see FIGURE 1.
Insert the 20 pin Modem header (supplied) into the printed
circuit boar d. The short pin portion of the header is inserted
into the PCB holes from the component side. Solder the header
pins on the bottom (trace side) of the circuit board. Solder
pi n s 1 and 2 0 f i rst to keep the header in place. S older all th e
other pins making sure you get a smooth solder flow. Use
caution when soldering to prevent over heating of the t races and
P C board bonding.
MFJ-2400 Instruction Manua l
B. INSTALLING THE 5 PIN I/0 CONNECTOR: Refer to FIGURE 2
Prepare one end of the five wire interface which has a 5-pin
connector at each end. This five wire interface is used
with all MFJ-2400 installations, therefore the five wire
interface is fitted with connectors at each end. In the
MFJ-1270, MFJ-1270B and MFJ-1274 installation, this 5 wire
interface uses a connector at the MODEM end only. Remove
one of the connectors by cutting the wires flush with the
connector edge.
You should now have a five wire interface composed of, one
connector with 5 wires, (brown, red, orange, yellow, and
green) approximately 5 inches in length extending from it.
Looking at the open end (holes) of the connector, pin 1 is
on the left, and pin 5 will be the last hole on the right.
When properly connected to the MFJ-2400 modem, the connector
pins count left to right, 1 to 5, Brown to Green.
Prepare the five wires by removing 3/32 inch of insulation
from the free ends. Tin each of the bare ends with solder
to prevent fraying of the wires, and to make it easy to
solder to the five locations shown in FIGURE 2. Solder the
wires to the points shown in the accompanying drawing. The
wiring is as easy as 1, 2, 3, 4, and 5 since the wires
follow the standard color code. (SEE FIGURE 2)
1 = BROWN 2
= RED
3 = ORANGE
4 = YELLOW
5 = GREEN
Connect the proper color wire to each of the 5 points
indicated in FIGURE 2.
Using care to be sure the MODEM PCB is correctly aligned
with the J4 pins, press the PCB into place on the J4, 20 pin header.
Attach P14, the 5 wire/pin interface I/0 connector to the
modem.
C: ADDING THE 2400 BPS "ACTIVE" INDICATOR (Optional)
Included in the MFJ-2400 modification kit is an LED which
can be added to the front panel of the MFJ-1270, MFJ-1270B
or MFJ-1274. The LED and pictorial drawing is supplied with
the kit in FIGURE 2. The 2400 BPS "LED" installation is a
user option. The location of this LED is the users choice,
however our experience shows that a small hole the size of
the LED just above the "STA" LED is adequate. This LED will
illuminate when the TNC is in the 2400 BPS mode, to give the u s er
an indication that 2400 BPS is "active". Connect the LED
tothe location marked "L1" on the modem PCB.
MFJ-2400 Instruction Manual
Negative is the short lead, and positive (+) is the longer
lead of the LED. Connect as shown in the illustration in
FIGURE 2.
D. SET DIP SWITCHES AT REAR OF TNC
To move between 300, 1200 and 2400 baud will require that
you use the last three DIP switches in the cluster of eight at
the rear of the MFJ-1270, MFJ-1270B or MFJ-1274. Use the
following switch settings for:
Switch Number 6 7 8
300 = ON OFF OFF
1200 = OFF ON OFF
2400 = OFF OFF ON
E. TESTING THE 2400 BPS MODEM OPERATION
Configure the TNC for normal packet use and make tests at
the normal packet speed. Next set the switches according to
the 2400 BPS settings above. Perform tests with other 2400
BPS stations in your area. This 2400 BPS mode should be
compatible with othe r 2400 BPS systems in the USA.
II. INSTALLATION FOR MFJ-1278 WITH REV. 6, 7, 8 MOTHER BOARD
Remove the four screws holding the top cover on the MFJ-
1278. Remove the cover and set it aside. Remove the "THRESHOLD"
knob and loosen the retainer nut of the "THRESHOLD" control.
Remove the two screws holding the front face plate, and
set aside. Remove the five screws which hold the main P C
board to the bottom plate.
Carefully lift the main PC board from the bottom plate and
place on a towel or soft surface, COMPONENT SIDE DOWN, front
toward you. Be sure no damage is caused to the components
on the top side of the PC board as you perform the 20 pin
header installation.
A: INSTALLATION OF THE 20 PIN HEADER: Refer to FIGURE 3
Installation of the 2400 BPS Modem is made to the MFJ-1278
by carefully cutting three traces at the modem header,
between pins 11, and 12, between pins 13, and
14,
and
between pins 17 and 18. CUT ONLY THE traces listed here. A
good magnifying glass is helpful while performing these
cuts.
Loading...