Installing The Voice Scrambler Board; Configuring And Modifying The Sc20-460 Board - Kenwood TKR-751 Modification Information

3 INSTALLING THE VOICE SCRAMBLER BOARD

It can install an optional Voice Scrambler board into the
TKR-750/850/751/851. This section describes how to
install the TRANSCRYPT SC20-460 in it. You can use the
KENWOOD service part (E37-0808-05) when installing
the SC20-460 board.
! Requirement Items
・ TKR-750/850/751/851
・ SC20-460
・ KENWOOD Part (E37-0808-05)
・ Cushion Tape
You must turn the power OFF before
installing the Voice Scrambler board.
3.1 Configuring and Modifying
the SC20-460 Board
1. Modify the SC20-460 board and change the RX Audio
Input method.
TKR-750/850/751/851 output a received audio after
De-emphasizing to input into the option board.
Therefore, it might be necessary to modify the voice
scrambler board.
(Confirm your SC20-460 is enabled de-emphasis.)
1-1. Cut the foil between E52 and E53.
1-2. Solder the position between E51 and E52 to
connect them.
1-3. Solder the position between E53 and E54.
3. Change the constant in conjunction with the TX/RX
Audio level.
3-1. Replace R1 with 100 kΩ and R3 with 100 kΩ in
conjunction with the RX Audio level.
3-2. Replace the R2 with 6.8 kΩ and R4 with 6.8 kΩ in
conjunction with the TX Audio level.
Before modification
R1, R3: 100 kΩ R1, R3: 100 kΩ (No modification)
R2, R4: 100 kΩ R2, R4: 6.8 kΩ
7
Before After
E51 E51
E52 E52
E53 E53
E54 E54
After modification
Modification Information (MOD)
R4
R3
Note:
" The required modification must be performed to avoid
problems, such as too small audio signals from the speaker,
or too loud synchronizing noise.
" Refer to the Voice Scrambler board's instruction manual for
details.
4. Disconnect the cable connected to the SC20-460
board.
5. Solder the KENWOOD service parts (E37-0808-05)
cables to the SC20-460 board. You must connect the
part as shown in the as shown below.
pin Connector (CN601).)
R2 R1
(Refer to 1.4 14-
Version: 1.02 USA