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Modifications 

Frequency Modification #1

Kenwood TM-V7A,  Beyond MARS Modification pictures.
Supplementary Info ASI-0031

 

Photo pictured with resistor removed

Place the radio on anti-static workbench and remove the bottom cover.

Inside the front of the radio is the vertical PC board. There will be two small chip resistors on the left side of the board.  (See photo)

Carefully remove the one with the number 0 on it aka R546.  This will be the one closest to the left near the ground spring. (See photo above) You can use a sharp wire cutter such as the Xcelite-175 to cut and scrape it away carefully keeping small amount of debris out of the radio.  You can also de-solder it from the board if you have the appropriate equipment. I've used two soldering irons and place one at each end of the chip resistor and comes off easy, or if you have a tweezers tipped iron like a Pace soldering station.

Replace cover and reset the microprocessor chip and reprogram the frequencies.

VHF  TX  136.995 - 173.995     RX  118-174
UHF  TX  410.000 - 469.995     RX  300-470

 

Frequency Modification #2

Kenwood TM-V7A,  MARS Modification pictures.
Supplementary Info ASI-0030

1. Disconnect power and coax

2. Remove bottom cover

3. Locate the two green jumper wires between the front panel and the Control board

4. Cut the green jumper wire on the left side. The wire may be tucked between the PCB and the front panel. 
    Carefully pull it out with tweezers so it can be cut.

5. Tape the exposed end of the wire or position the wire so that the exposed ends do not make contact with
    the PCB or chassis. Be careful not to pinch the wire when the bottom cover is installed.

Replace cover and reset the microprocessor chip and reprogram the frequencies.

VHF 142.00 - 151.995 Mhz TX        118.00 - 174.00 Mhz RX
UHF 420.00 - 449.995 Mhz TX        420.00 - 470.00 Mhz RX

 

MC-52/53DM Microphone 

"Hot" Microphone Element
Application note AAN-0021R1

The microphone element of the MC-52/53DM is "Hot", Sending microphone audio continuously when the transceiver is used in the remote control mode. If the microphone picks up DTMF from another source it can cause the radio to apparently malfunction. The transceiver is not broken, only taking the DTMF as a command to perform some function. The following modification will disable the microphone element until the microphone PTT key is pressed.

Procedure:
Add a DTC143ES digital transistor as shown in the accompanying diagram. The Emitter and Collector are soldered across the microphone element and the Base is soldered to the junction of D2 and D3. Note that the transistor is mounted with the part number facing the PCB.

 

MC-52/53DM Microphone
 
Audio Frequency Change
Application note AAN-0022

Some customers have asked Kenwood to offer a change to the MC-52/53 audio frequency response curve. Whole there is a variety of changes that can be made, the following was selected for its ease of modification and overall response curve. This change effectively reduces the high frequency components of the transmitted audio, allowing the listener to hear more midrange response

Procedure:

1. Open the microphone by removing the three back panel screws.

2. Either replace r& with a 15K ohm resistor or install a 33K ohm resistor in parallel with R7.

3. Add a 0.1uF capacitor between the junction of R9/C6 and ground (mic element lead). Any standard ceramic
    capacitor will work.

 

 

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