Modifications for the Kenwood TM-741

TM-741ATE Frequency enion


Phase 1
  1. S1ide the release knob on the front panel to the right and remove the panel (be careful with the cable between the panel and the main unit.)

  2. Cut the green wire located in the left side (tape the bare ends of the wire to prevent shos.)

  3. Switch the power on (a melody sounds to confirm the change.)
Phase 2

  1. Unplug the connectors of the cable between the panel and the main unit.

  2. Remove the two screws on the rear of the panel and open the rear of the case.

  3. On the left side of the lithium batterv there are four jumpers marked R54, RSi, R5ndR57 corresponding respectively to bO, bl, b2 ana b3 bits described beloSSt the four bits as required for your country:
- European Countries:
mode5
b3 = O
ba = 1
b1 = O
bO = 1

- USA, Canada and Asia:
mode $0-3

b3 =0
b2 = O
b1 = 1
bO = 1
WARNING: O => jumper , 1 > no jumper.

d) Refit the rear of the case by reversing the order of disassemoly.

Frequency range after modification (*)
+--------------------------------------------------------------+
|      ||  rx range ||  tx range ||           SHIFT            |
| unit || min | max || min | max ||   EUROPE    | USA CAN ASIA |
|------||------------------------||----------------------------|
|   28 ||  18 |  54 ||  26 |  45 || +/- 100 KHz |     idem     |
|   50 ||  40 |  90 ||  46 |  76 || +/-   1 MHz |     idem     |
|  144 || 118 | 174 || 136 | 174 || +/- 600 KHz |     idem     |
|  220 || 215 | 260 || 215 | 235 || +/- 1.6 MHz |     idem     |
|  430 || 410 | 470 || 410 | 470 || +/-1.6,-7.6 | +/-    5 MHz |
| 1200 ||1100 |1400 ||1100 |1400 || +35, -6 MHz | +/-12,-20MHz |
 --------------------------------------------------------------+

TM-741a/e AM recleppion with 28 and 50 mhz unit


a) Press the F key, then press BELL; key within ten seconds. An A is displayed at the hundred-MHz position to indicate AM mode.

b) To rr to FM mode press the F again, then press the BELL; within ten seconds
TM-741 A/E 900 MHz band receptton with 430 MHz unit


To change to the 900-MHZ band. select the 430-MHnd, then press and hold down the [MHZ; key for at least a second. NOW 850.000 (initial setting) is displayed.

To return to the 430-MHZ band, press the [MHz] key again for at least a second.

Addling a secondary 900-MHz dedicated antenna at the 430-MHZ unit

  1. remove the power supply cable from the power supply or battery.
  2. remothe 430-MHz band unit with care.
    For removal procedure see the instructionNAL - unit INSTALLATION, reversing the order of the procedure and... using the brain:
  3. Remove the shield plate (12 screws.)
  4. Solder a coaxial cable (0.8 d) to the input side of IC9 (center is aligned with the IC9, ground at right side.)
  5. Pass the cable through the notch and install the shield plate.
  6. Reassemble the main unlit.

TM-741A/E memory channel doubling


Each band can be switched to the normal memory C100 channels) and rear memory (100 channels). Each band can contain 200 channel and... yes, a total of 600 channels can De used for three bands

SORRY! This function can be enabled only by extending the receive frequency see bulletin #1 of this FREQUENCYEXTENSIoNSNEVERENDHISTORY.)

To switch the memory, hold down the F; key and press the rev; key:

Normal Memory 100 ch <--> Rear Memory (100 Ch)

The functions of the rear memory are the same as the normal memory, but memory channels are displayed as follows (rather than 01 to 00):

a1 -b0 ==01-10
b1-c0==11-20

c1- d0== 21-30
d1-eo==31-40        

e1-fo==41-50    
f1-g0==51-60        

g1-h0==61-71    
h1-i0==71-80        

.1-j0==81-90 
j1-aa==91-100

TM-741A/E extended paging functions


Preliminary

Cut the frequency extension jumper as described in Phase 1 of the bulletin #1.

Answer back function

Hidden function of the paging function.
If the answerback function is on, the code of the local transceiver is automatically transmitted to the other tranciver when the correct code is received to confirm the code has been received.

OPERATION

After the correct code is received, if there is no busy signal, the code of the local transceiver is automatically trangmitted to the other transceiver.

ON/OFF      To turn the answer-back on and off, hold down the
            F; key and press then the Call key.
Automatic release function

Hidden function of the paging function.

OPERATION

If the automatic release function is on, paging is terminated automatically when transmission ends after a call is received.

ON/OFF      To turn the function on and off, hold down the
            [ F; key and press then the jSHIFT; key.

TM-741/E DTE DISPLAY Format


The normal date format is YEAR-MONTH-DAY. It can be changed to YEAR-PAY-MONTH.

  1. Remove the front panel and locate R60 and R61
    (Where is Holmes?)
  2. Move R61 (that is below R60) to the left.
  3. Repack the front panel with care.

TM-741A/E DC ERDISPLAY


Make the following change to display the sb line voltage on the? memory channel section when the tieis displayed.

  1. Remove the front panel and loca R60 and R61
    Where is Holmes?)
  2. Move R60 That is above R61) to the left.
  3. Repack the front panel with care.
Since the voltage of the Sb line to the panel is displayed, it changes due to the loss caused by the wie nd connctor
TM 741A/E headlight linkage dimmer


Make the following change to reduce the dimmer level by one step when the headlight is turned on (d4 remain unchanged).

  1. Install DTC144EK on the panel printed circuit board (below R60 and R61
  2. connect the load from the ILUMI pin of the panel printed circuit board to the 12 V side Where 12 V is output whene light is turned on) of the position light of the car.

TM 741A/E game mode


Simple me, such as a roulette game and a shooting game, and music can be played using the frequenay display.

To enter game mode, hold down the F] key and the MUTE key, and switch the power on.

1-2-3 is shown on the display, band SEL A; selects Roulette, BAND SEL B; selects Shooting, and jBAND SEL C; selects Music.
To return to game selection mode, press the VFO] key.
To exit game mode, press the microphone key or switch power off.

Roulette Game

* When the roulette game starts, the display shows [000], the transceiver enters the receive mode with the power on, and th three digis bein to rn raidly.
, Wen the MUTE key is pressed, [000 on the display can be changed: BAND SEL A; stop the leftmost digit, BAND SEL B; stops the middle digit, and BAND SEL C] stops the rightmost digit. Other keys are not accepted.

A if the three digits match, the LED and illumination lamp flash and sound effects are produced.

* if 1231 ;E displayed, a fanfare sounds. If the MUTE; key is pressed game mode is exited and the transceiver functions normally.

Shooting game

* When the shooting game starts, your score is shown in display: section A, and cannon balls, target and remaining cannons are shown in display section C, starting from the left.

A If the LOW; key is pressed, the game starts. The "number" attacks from the left of display 8. Take aim at the enemy "number" with the [TONE; key key, and shoot with the [mute key. You win if 16 enemies are shot per screen. Thirty cannon balls can he used per screen. Each time you clear a screen, the speed increases. If eight screens are cleared, the first screen returns. The process is repeated.

When the music feature is selected, ENJOY SOUND PLAY; is displayed and the following tones can be produced:
  MR   = A
  KHz  = A#
  CALL - B
  F    = c
  BELL = C#
  TONE = D
  REV  = D#
  BTSS = E

MUTE   - F
CScL A = F#
BSEL A - G
CSRL B = G#
BSEL B = A
CSEL C = A@
BSEL C = B

Kenwood TM-741a GAME Dox


Introduction:

There are actually three GAMES "hidden" on the Kenwood TM-741a Multiband Transceiver. These are UNDOCUMENTED and I'm not exactly sure who originally found these games??.. (I came across a brief description of these hidden games on rec.radio.amateur.misc on UseNet, but no one had the complete original Post!)

How to access "Game Mode":

1) Turn OFF the TM-741a.
2) Hold the [F] + [MUTE] and turn ON the TM-741a.

(You should see: -1- -2- -3- on your display, you're now in "Game Mode"!!)

3) Select the Game you wish to play by hitting the appropriate Band Select Button. ( -1- = Band Sel 1 ; -2- = Band Sel 2 ; -3- = Band Sel 3 )

-1- ==> SLOT MACHINE Game

-2- ==> SPACE INVADERS Game

-3- ==> MUSICAL KEYBOARD

NOTE!
The [VFO] will always exit you to the Main Game Menu (-1- -2- -3-).. The [MUTE] will normally Start the Game.

Game #1: SLOT MACHINE:

To play... Hit [MUTE] to start the numbers tumbling. Starting from the left and proceeding to the right, hit the Band Select Buttons to stop each number! If you don't get a 3-in-a-row match, the radio plays a sound and the game is over. ([MUTE] to play again). If you match 3-in-a-row, then...well I won't spoil it for you!.. (It's neat!!)

Remember; [VFO] to return to the Game Menu.

Game #2: SPACE INVADERS:

The Display... You will see the following display:

000000 ------ 0-0

(Score) (Invaders) (Selected Number - Number of Lives Left)

To play... Hit the [LOW] key to begin. The radio will then put a random number from 0 - 9 in the first position in the dashes.. ( 4----- ) you must then use the [TONE] key to select the number the radio selected and then quickly hit the [MUTE] key to "fire" it. The number will then disappear and a new one will appear!.. If you don't act fast, the number will move to the second dash and another random number will appear, ( 84---- ).. If you're not keeping up, eventually the numbers will reach then last dash line and you will lose a life!!.. (Once all lives are lost, the game is over!) Also, you must "destroy" 30 numbers before moving onto the next round!.. Each round will start getting faster and faster!!.. So be prepared!! (It really gets TOUGH!!) All throughout the game it will keep score of how many "hits" you made.. (I believe it's 10 points a hit, I think!)..

Remember; Hit [VFO] to return to Game Menu.

Game #3: MUSICAL KEYBOARD:

I don't think this is actually a "Game"??.. What I've been able to figure out is that when you select this "game" the following message appears on the display: Enjoy Sound Play

At this point, the whole keypad on the face-plate of the TM-741a is a "Musical Keyboard"!!.. Try it, hit any of the keys, Band Select Buttons; Cont Sel Buttons; [MUTE]; [TONE]; [MHZ]; Etc...etc..etc... (Except for the [VFO] key, that returns you to the Game Menu!)
Display test


Hold down F and MHZ while turning on power. This activates the display test mode where all segments and indicators are lit. Note the "ACC" indicator at the lower right. ACC is not defined in the manual, however I saw it come on once one night after I started the car with the radio turned on. The display lit up ACC and the UHF frequency display showed some sort of HEX code (a ROM checksum maybe?).
Hearing birdies in the 440 MHz position


Nov 91

Are you hearing "birdies" in the 440 MHz position on your new Kenwood TM-741A?

I've had the problem with mine, and have been talking with other people who are having the same problem. Kenwood couldn't duplicate the problem and returned my 440 deck. The problem appears either as weak wandering carriers, or intermods with other input signals. Seldom is the signal strength greater than S2, but the squelch stays open most of the time. K6DYD has traced the problem to instability in the RF front-end (Q1, Q2), which is electronically switch out of the signal path by IC8 when out-of-band frequencies are selected. The solution appears to be placing a 220-ohm 1/4-watt resistor from pin-10 of IC8 to ground--this damping in what appears to be a signal leakage path prevents the unstability or parasitic oscillations causing the problem. He further observed that, if the control head is modified for full-frequency operation by removing the jumpers labeled R54 and R55, the RF preamp is continuously removed from the signal path unless the GREEN WIRE on the processor motherboard has been cut. During proper operation, pin-9 of IC8 should change state when tuning in-band vs. out-of-band.

The 220 MHz deck seems to enjoy having its VCO modulated by AC coming in the power cord. Alternator whine is annoyingly present during both transmission and reception. No cure identified yet.

For those of you that want 220-440-1200, simply remove the 144 module, move the power cable into another module, restuff the frame, restart while reseting the VFO limits... Works fine.

I would appreciate hearing from any of you having similiar problems; writing to customer relations is also a good idea. If you're considering one of these units but don't want the 2M deck, also write Kenwood. I've lost count of people who said they wanted this option. I'd like to be able to get all the decks separately from the bare frame.

All in all, it's a nice radio--it just has growing pains; the sooner Kenwood owns up to the problems and fixes them, the more they'll sell.

-Bob Buaas K6KGS (Internet: buaas@nosc.mil) (Phone: 714/968-0070)
TM-741A/E repeater modification (transponder functions)


WARNING:
Extended continous transmission may cause a failure of the equipment. See "transmission time limit" below.

Preliminary hardware modification
  1. Loosen the four screws on the side of the set.
    Remove the four screws on the bottom of the set.
    Remove the bottom of the case.

  2. Locate the two jumpers on the Control Unit, on the opposite side of the panel (see in figure, below.)
      +--------------------------------------------------------------+
      |                    | | <----- remove (blue)                  |
      |                                                              |
      |                                                              |
      |          CONTROL UNIT                                        |
      |                                 ________                     |
      |                                |  ic 2  |                    |
      |                                |________|                    |
      +--------------------------------------------------------------+
                               panel side
    
  3. Remove the blue chip jumper (0 OHM). Use a soldering iron with a thin tip in order not to damage other components or patterns.

  4. Refit the rear of the case by reversing the order of disassembly.
Fixed-band repeater operation

With the fixed-band repeater, the transmission band is fixed, and if a signal come in on the remaining band, and the BUSY turns on, the transmit mode is entered and modulation is done using the received signal.
  1. If the option band is present, turn off one of the three band.

  2. Set the frequencies of two bands (rx/tx split are also permitted.)

  3. Set a band as the transmission (PTT display) and operation (green indicator) band (press the band select key.)

  4. Hold down the [F] key for at least a second (the red led flashes), then press the [MUTE] key.
Cross-band repeater operation

When the cross-band repeater function is being used, a signal enters one of two bands. Busy turns on, the other band enters the transmit mode and modulation is done with the received signal.
  1. Set the frequencies of two bands (rx/tx repeater split are also allowed.)

  2. Set a band as the transmit band (PTT display) and the other as the operation band (green indicator). This arrangement can be reversed.

  3. Hold down the [F] key for at least a second (the red led flashes), then press the [MUTE] key. The dots on both frequency display flash, and the cross-band repeater works. Only reception is possible in the remaining band.
Dual-in repeater operation (when the option band is installed)

With the dual-in repeater, the transmit band is fixed, and if a signal comes in on one of the other bands, Busy turns on, transmit mode is entered and modulation is done using the received signal.
  1. Set the frequencies of all three bands.

  2. Set a band as the transmission (PTT display) and operation (green indicator) band (press the band select key.)

  3. Hold down the [F] key for at least a second (the red led flashes), then press the [MUTE] key.
    The dots on the frequency display light.
Turn-off repeater

To turn the repeater off, hold down the [F] key for at least a second (the red led flashes), then press the [MUTE] key.
The state before setting returns.

Repeater transmission time limit setting

The repeater transmission time limit is set with the time-out timer (TOT). The time can be set to 3, 5, 10, 20, 30 minutes, or OFF. (See the item about the TOT of the main unit.)

Be happy and 73 de Antonello is0xse,
Cagliari, Sardegna, Italia, Europa... MONDO!!!!!
IS0XSE @ IW0UHD.ITA.EU
TM-741a All-Band mod for new Kenwood Tri-Bander


To enable FM transmit from 136-174, 410-470, do the following:
  1. Remove the front panel.
  2. Don't cut the green wire. If it is cut, splice it back.
  3. Disconnect front panel unit cable.
  4. Remove two screws in front panel back and remove rear cover.
  5. Locate row of resistors next to Lithium Battery.
  6. Remove R54 and R55 - clearly marked, the two nearest the battery.
  7. Reassemble. No MPU reset necessary.
Note: Removing only R54 enables MARS/CAP only. Removing bothenables all.-fred--

Fred Lloyd AA7BQ
From: tonyb@ka.NOvell.COM (Tony Bamberger)

I have the following corrections to Fred's mods for the new kenwood TM-741a multi band radio...> Hot off the presses...>
>   to enable FM transmit from 136-174, 410-470, do the following:>
>   1. Remove the front panel.
>   2. Don't cut the green wire.  If it is cut, splice it back.
>   3. Disconnect front panel unit cable.
>   4. Remove two screws in front panel back and remove rear cover.
>   5. Locate row of resistors next to Lithium Battery.
>   6. Remove R54 and R55 - clearly marked, the two nearest the battery.
>   7. Reassemble.  No MPU reset necessary.>
>   Note: Removing only R54 enables MARS/CAP only.  Removing both
>   enables all.
This is not 100% correct. According to the mod sheets i have from kenwood, you have to cut the green wire and remove R54 for mars/cap mod.
For the DC-light mod, you resplice the green wire (if cut) and remove both R54 and R55.
One side note, no reset is needed as mentioned above, but it does wipe out the values stored in the vfo memories (at least on the radio's mod'ed around here). As long as we're talking mods...
For extended receive only other than the 144 & 440 (which are already extended) you only cut the green wire. This gives you 10 meter coverage from 18-54 mhz, 6 meter coverage from 40-90 mhz, 220 coverage from 215-260 mhz and 1.2 GHz coverage from 1100-1400 mhz.

Note that these only apply if the specific module is installed in the radio (i.e. 10 meter, 6 meter, 220 or 1.2 ghz)...


Go Back To The Kenwood Mods Page

Go Back To The Main Modifications Page

Go Back To The CB / HAM Radio Main Page

Go Back To The Main Home Page


Copyright © The Defpom 1997-2008

http://www.radiomods.co.nz/