Modifications for the Kenwood TM-321

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.
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).
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.
Packet mod for TM-321


8 Nov 89

From: rfc@briar.philips.com (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.


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