Icom IC-718, Service Manual Addendum

Page: 161 / 206

4 - 8
4-5 POWER SUPPLY CIRCUITS
4-5-1 PA UNIT
4-5-2 LOGIC UNIT
4-5-3 MAIN UNIT
LINE
HV
14 V
DESCRIPTION
The voltage from an external power supply
passed through a fuse (F1).
The same voltage as the HV line passed through
the switching relay (RL1).
LINE
8V
T8V
R8V
–5V
PAT8
T13V
R13V
DESCRIPTION
Common 8 V converted from the 14 V line and
regulated by the 8V regulator circuit (IC3005).
8 V for transmitter circuits converted from the 14
V line using TX signal and regulated by the T8V
regulator circuit (IC3005).
8 V for receiver circuits converted from the 14 V
line using RX signal and regulated by the R8V
regulator circuit (IC3005).
Common –5 V converted from the 14 V line and
converted by the –5V DC-DC converter circuit
(IC3501, D3502). The voltage is applied to the
AGC (Q1805, D1803), ALC (IC1701) and AF
selector (IC2102), etc.
8 V for transmitter circuits converted from the 8
V line and regulated by the PAT8 regulator circuit
(IC3005).
13 V for transmitter circuits converted from the
14 V line using TX signal and regulated by the
T13V regulator circuit (Q3801, Q3802). The volt-
age is applied to the TX/RX switching relay (FIL-
TER unit; RL13).
13 V for receiver circuits converted from the 14 V
line using R8V signal and regulated by the R13V
regulator circuit (Q1001, Q1002). The voltage is
applied to the receive 1st mixer circuit
(Q1101–Q1104).
LINE
H5V
5 V
DESCRIPTION
Common 5 V converted from the HV line and
regulated by the H5V regulator circuit (IC5).
Common 5 V converted from the 14 V line and
regulated by the 5V regulator circuit (IC6).