Modifications for the Kenwood TM-942

Microprocessor Change, TM742/942


K E N W O O D
A M A T E U R - R A D I O - S E R V I C E - B U L L E T I N

BULLETIN # 1042
MODEL: TM-642A/TM-742A/TM-942A
SUBJECT: Microprocessor Change

This bulletin supercedes ASB-1033.

Symptom:

Reports of problems with microprocessor lock-up when using S-meter squelch, problems with storage/recall of PL tone frequencies of 203.5 Hz. and/or 114.8 Hz., or problems with a lack of transmit on the UHF band modules during Remote operation can be corrected using the changes noted in this bulletin.

Notes:
  1. All TM-642A transceivers work fine and do not require any changes.
  2. TM-742/942's that exhibit any of these symptoms with serial numbers between 412XXXX and 509XXXX need only change IC1 on X53-3460-21 B/2.
  3. TM-742/942's that exhibit any of these symptoms with serial numbers of 412XXXX and below must also change IC1 on X54-3130-11.
  4. TM-742's with serial numbers of 509XXXX and greater have had these changes incorporated in production.
  5. Some TM-742's and TM-942's below serial number 509XXXX were returned to Japan for modification. If the unit that you have has a black dot on the box near the serial number it has already been modified and requires no further action
Parts Required:
Qty    Description    Old Part No.     New Part No.       Circuit Description

1      Microprocessor HD6433388A07F    HD6433388A22F      IC-1
                           or
                      HD6433388A14F                         

1      Microprocessor HD404719A26H     HD404719A32H       IC-1
Caution:
This modification requires advanced surface mount soldering equipment that is rated for CMOS circuits. It also requires familiarity with advanced surface mount soldering techniques. If you do not have the proper equipment or knowledge do not attempt this modification yourself.
Attemping to remove and replace either IC without the proper equipment and techniques can easiy damage the circuit boards and void your warranty.
Seek qualified assistance from your closest Kenwood Service Center (Long Beach, CA, or Virginia Beach, VA).

Time required for this moditication is 90 minutes or less.
28 MHz/50 MHz RC TX Failure


K E N W O O D
A M A T E U R - R A D I O - S E R V I C E - B U L L E T I N

BULLETIN # 1029
MODEL: TM-742A/TM-942A
SUBJECT: 28 MHz/50 MHz RC TX Failure

Symptom:
The 28 MHz and 50 MHz modules do not transmit after direct frequency entry from the microphone when the radio is switched to the RC function.

Corrective Action:

Replace IC1 on the Control Unit X53-3460 B/2 and IC1 on the Display Unit X54-3130 A/3.

Parts Required:
Qty     Description     Kenwood Part No.                Circuit Description

1       Control Unit microprocessor     HD6433388A07F           IC1
1       Display Unit microprocessor     HD404719A32H            IC1
Caution:
This modification requires soldering equipment rated for CMOS type circuits. It also requires familiarity with surface mount soldering techniques. If you do not have the proper equipment or knowledge do not attempt this modification yourself. Seek qualified assistance.

Time required for this modification is 1.5 hours or less.
Modification of TM-742 & 942


pen the lower panel of TM-742.

****** There are TWO version. Please check which version your rig is.******


                      FRONT PANEL IS UPER SIDE

      ___                               ___    ___    ___     <<=== BAND SEL
   ---|-|-------------------------------|-|----|-|----|-|--------
  |                                                              |
  |______________*_______________________________*_______________|
  |     11                    2222                               |
  |    111                   22   22                             |
  |     11                      22                               |
  |     11                    22                                 |       
  |     11                   22222222                            |
  |                                                              |       
  |                                                              |       
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  1. ****** FOR OLD VERSION ******
    SEE THE POINT OF [ 2 ] .If you can find a small board masked with black sponge , your TM-742 is OLD VERSION.
  2. On right side small board , there are three lines. Make short circuit with midlle line and lower line.
  1. ****** FOR NEW VERSION ******
    SEE THE POINT OF [ 2 ] . If you can not find a small board , your rig is NEW VERSION.
  2. SEE THE POINT OF [ 1 ]. There is a chip [ 2R7 ] . And below this chip [ 2R7 ] , there are small chip [ 473 ] . 
         [ GRAPHIC IS FOR JA VERSION ]
 *-*-*-*-*-*-*-*
         R R R X        R =  chip [ 473 ]
 * * * * * * * *
 * * * * * * * *        Make short circuit two X point.
         X     R        Maybe on your TM-742,there are chip [ 473 ]
 *-*-*-*-*-*-*-*        with different patern. This graphic is for
                        JA version.  So please try until modification
                        will succeed.
OPERATION
  1. ON 144MHz press band sel more than 1sec . mode change AM <-> FM.
  2. ON 430MHz ditto band change 430 <-> 870
  3. ON 1200MHz ditto 1200 <-> 870
  4. [F] + BELL -> repeater dual RCV.
  5. 118-136MHz mode chang to am automaticaly.
  6. X-band repeater operation. Select one band by [BAND SEL] select onother band by [CONT SEL]. Press [F] key more than 1sec. Press [MUTE] Key. X-band operation will work. Press [F] then [MUTE] key -> cancel X-band repeater operation.
73s DE JP1LRT @ JL1YVX.10.JNET1.JPN.AS
YOSHIHARU "KEI" TSUKUURA
TM-742/942 Beyond Mars/CAP Mod. Guide


Procedure:
  1. Detach the front panel from the main chassis.
  2. Remove the bottom cover of the transceiver by removing the 4 screws on the bottom of the cover and loosening the 4 screws on the side of the unit.
  3. Orient the radio so the bottom is up and the front panel area is near your chest. Near the front panel area you will find a large board, this is the control unit.
  4. Remove the chip resistors "Y" noted in the diagram below, and reinstall them in position "Z" as shown.
  5. Reinstall the bottom cover of the transceiver and reattach the front panel.
  6. Reset the microprocessor. Press and hold the MR key while the power is switched on. Then release the MR key. This will erase all operator programmed data.
  7. The frequency range after modification will be: 
            28  Mhz Band:   RX:   18.0 thru  54.0 Mhz
                        TX:   26.0 thru  45.0 Mhz
        50  Mhz Band:   RX:   40.0 thru  90.0 Mhz
                        TX:   46.0 thru  76.0 Mhz
        144 Mhz Band:   TX:  136.0 thru 174.0 Mhz
        220 Mhz Band:   RX:  215.0 thru 260.0 Mhz
                        TX:  215.0 thru 235.0 Mhz
        440 Mhz Band:   TX:  410.0 thru 470.0 Mhz
        1.2 Ghz Band    RX/TX: 1100.0 thru 1400.0 Mhz
    Please note that these are theoretical ranges only. Not all radios will be capable of tuning the entire range. 
              Control Unit X53-346X-XX A/2
      _____________________________________   
                                          I
                                          I   Remove Y resistors and 
                         ---- ----        I   reinstall in position Z
                            Z IIYY        I
                         ---- ----        I
                         oooo oooo        I
                         ---- ----        I
                         IIIY   ZZ        I
                         ---- ----        I
                                        2 I
                                        R I
                                        7 I

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