Modifications for the Kenwood
TM-321
19-07-1998 TM-321A Mars/cap
mod
To give the TM321 tx coverage from (142 0r 143, don't
remember which) to 151.995 mhz, remove the top cover.
Look for a loop of
wire comming from the display area (the board with the CPU) and going right
back.
Cutting this wire and then doing a CPU reset is all you need to
do.
Takes about 2 minutes. Be sure that the ends of the wire don't short
to something.
19-07-1998 TM-321A Weak mic audio
fix
A quick and dirty fix for the knwd tm231a low mic output:
knwd comes out with a fix which is to bypass r 63 (3.3K). R 63 and r64 form a
voltage divider at the input to the mic amp. R63 is on the bottom of the rig.
With the bottom cover off and the front of the rig facing you, locate the mic
amp board 3610 which stands vertically off the mother board. Follow the 3rd pin
from the left to r63. A jumper here gives the tx audio a nice boost. Be sure to
readjust the dtmf output in the mic (the only pot in the mic).
19-07-1998 TM-321A Mod to Squelch thw audio
at mic pin 6
The following is an easy mod to squelch the audio at
mic pin 6 for tnc's
Without true dcd: obtain from kenwood a 2sd1757(k)
(surface mount transistor). Install emitter to mic pin 8, collector to mic pin
6, and jumper from base to the unused pin on connector 202. Using the unused pin
rather than running the jumper to the mother board preserves the plug in feature
of the front panel.
Connect one end of a 4.7K resistor (i used a 6.8K) to the
mute line (ic 5 pin 7), and connect the other end to the unused pin of connector
4, which mates with connector 202. This new circuit is a close copy of the af
mute circuit that squelches the rx audio at the speaker. It works perfect with
my paccomm micropower 2. The hardest part of the mod is removing the locking
ring around the mic connector. I used a modified table fork! good
luck.
19-07-1998 Packet mod
for TM-321
8 Nov 89
From: [email protected] (Robert
Casey)
The following is an easy mod to squelch the audio at mic pin 6
for tnc's
Without true DCD: obtain from Kenwood a 2SD1757(K) (surface
mount transistor). Install emitter to mic pin 8, collector to mic pin 6, and
jumper from base to the unused pin on connector 202. Using the unused pin rather
than running the jumper to the mother board preserves the plug in feature of the
front panel.
Connect one end of a 4.7 K resistor (i used A 6.8 K) to the mute
line (IC 5 pin 7), and connect the other end to the unused pin of connector 4,
which mates with connector 202. This new circuit is a close copy of the af mute
circuit that squelches the RX audio at the speaker. It works perfect with my
paccomm micropower 2. The hardest part of the mod is removing the locking ring
around the mic connector. I used a modified table fork! Good
luck.
16-04-2000 TM-321A
Loss of TX audio with MC-48B
Author: Trio-Kenwood Communication,
inc.
Service Bulletin no. 935 (2-6-1988)
When en MC-48B is used with the TM-321A, transmit audio may be suppressed do
to RF feedback. This occurrence is restricted to mobile operation where the
antenna is in close proximity to the microphone. The audio can be restored by
adding a 100 pF capacitor directly to the mic element terminals.
Required parts:
100 pF, 50V capacitor. Part number CK45B1H101K or
CC45B1H101K
- Remove the 3 screws from the mic case (See figure 1). Carefully open the
case.
- Pull the PC board, PTT knob, and PTT micro switch out of the mic case to
expose the mic element cover (See figure 2).
- Remove the 3 screws and mounting clips (See figure 3) securing the element
cover. Remove the PTT spring. Pull the mic element and cover out of the
case.
- Remove the element from the rubber cover.
- Install and solder the capacitor directly to the mic element terminals
where the brown and white wires are connected (See figure 4). To avoid
damaging the element, use a low wattage soldering iron.
- Carefully assemble the mic by reversing steps 1 - 4.
This modification may be covered under warranty.
Time required for this
modification is ½ hour or less.