Modification - Kenwood TKR-750 Service Manual

1. Modification for Sinking the Collector Current Up
Auxiliary output 1 and 2 can each be modified to sink up
600mA of the collector current. The following modification
should be installed when Auxiliary output 1 or 2 is used to
control external equipment.
1. Remove D625, R755, and R769 for Auxiliary output 1
(D624, R756, and R770 for Auxiliary output 2) on the
component side of the control section for TX-RX unit
PCB.
2. Install $Q608, $Q612, and $R761 for Auxiliary output 1
($Q607, $Q611, and $R759 for Auxiliary output 2) on the
component side of the control section for TX-RX unit
PCB.
$Q607, $Q608, $Q611, $Q612 : DTD114EKA
$R759, $R761 : 3.9kΩ (RK73GB1J392J) chip resistor.
3. Change R801 for Auxiliary output 1 (R797 for Auxiliary
output 2) from 1kΩ (RK73GB1J102J) to 0Ω (R92-1252-
05).
By making this modification, Auxiliary output 1 and 2 can
now sink up to 600mA each.
TX-RX unit (B/2)
Component side
IC602
R756
$Q607
IC623
$R759
R755
$Q608 $Q612
Fig. 1
5V
Add $R761
($R759)
3.9kΩ
Add $Q608
Add $Q612
($Q607) ($Q611)
DTD114EKA DTD114EKA
Shift
register
Remove
IC623
R755 (R756)
0Ω
Fig. 2

MODIFICATION

R770
$Q611
CN605
$R769
R769
C681
5V
Remove
D625 (D624)
DA204U
TEST/
SPKR
Remove
R769 (R770)
0Ω
2. DC Source Switch
To prevent the power supply from turning off due to
misoperation of the DC source switch on the front panel or
accidents (tampering) after installation, the main unit can be
kept on regardless of the on/off of the DC source switch on
the front panel.
Short the PSW land near K1 relay by soldering.
TX-RX unit (A/2)
Component side
CF1
WIDE
PSW
K1
Fig. 3
TKR-750
CF2
NARROW
15