HYT TR-800, Service Manual

Page: 39 / 90

TR-800 Service Manual
37
Circuit Description
Repeater Communication Interface & Display Unit
Setup/Knockdown (U0107D, Q0101, Q0103, Q0106, Q0107 and Q0108):
The setup/knockdown mode at power-up can be configured via the HR-800 programming software. The
electronic switches, Q0106 and Q0108, cause the setup/knockdown action by applying or removing
voltage at the ignition control, pin15, of “J0102-Main”. After power-up, the setup or knockdown mode
may be changed remotely with a signal from pin10 of “J4-Slave” or locally through the front panel SETUP.
S0102 is a momentary contact switch that is debounced by the Q0103/Q0107 latch circuit. The orange
SETUP LED, CR0102, illuminates to indicate the setup mode.
As the setup/knockdown circuit goes from the knockdown to the setup mode, Q1 is momentarily turned
on by Q0108 via the C0101/R0103 timing circuit. The push-to-talk (
PTT
) input of the slave radio, pin8 of
“J4-Slave” is pulled low by Q0101 and keys the transmitter. The Rx LED, CR0105, will briefly flash during
the moment that Q0101 is conducting.
Forward Audio Routing (U0104A, U0104D, U0115 and U0102B):
The audio gate, U0104D, quarter of an analog switch BU4066B, enables and disables the audio from the
front panel MIC audio input. U0104D is turned on with an active high DC level driven at the output of
U0111_014 once a front panel
PTT
input is detected. The filtered audio output from pin5 of
“J0104-Slave” and the flat audio output from pin12 of “J0104-Slave” are respectively routed to VI2 of a
D/A converter, U0115. The audio gate pairs of U0112A/U0112C and U0112B/U0112D are controlled by
output of AUX4 “J4-Slave”. U0104A is enabled once a valid signal is received and will route the audio to
the DAC and transmitter. The external audio input, ACC Relay audio, is routed to the DAC U0115_VI1
and digitally adjusted to appropriate level for transmitter. The output from U0115_VO1 is applied to the
second half of U0102, a buffer amplifier. All the forward audio will be mixed together and routed through
S0101-5 to the main microphone transmitter audio, pin2 of “J0106-Main”.
Reverse Audio Routing (U0115, U0104B and U0104C):
Part of the front panel MIC audio is routed to the input of U0104B, quarter of the analog switch BU4066B.
The output of U0104B is also controlled with an active low input by the front panel
PTT
. Audio present on
pin5 of “J0102-Main” is routed through S0102-7 to VI5 of U0115, which is used to adjust the audio level
for proper deviation. As with the forward direction, the audio output of VO5 is applied to an analog switch
U0104C. This switch turns on only if a valid signal is detected and pin6 of U0104 goes high.
Forward and Reverse Key-up (Q0102, U0103, U0107, Q0105, Q0111 and Q0116):
When a valid input signal is present at the slave radio, pin6 of “J0104-Slave” will be pulled low and turn
off Q0105 through two NAND gates, U0107B and U0107C, along with RPT enable trigger. A high DC
level output from Q0105 will be applied to pin37 of U0110 and key the master radio
PTT
through output
from U0111_013. The red Tx LED, CR0106, illuminates.