TR-800 Service Manual
38
When the reverse key-up function is enabled, as in the bi-directional repeater configuration, S0101-8
must be on. Q0116 is a DC amplifier (buffer) for the Rx carrier signal from pin6 of “J0102-Main”. An
active low state at the input of the NAND gate U0107A, one quarter of a MC14011B, will be conversed to
a high state to drive the buffer for the Rx carrier signal. The active low level of Rx carrier signal, along
with the OPT enable signal, causes a series of NAND gates, U0103D, U0103C and U0103B to generate
a high DC level to turn on Q0102. The output of Q0102 is pulled low for pin8 of “J0104-Slave” and keys
the transmitter of slave radio. The green Rx LED, CR0105, illuminates.
Q0111 is used to prevent the simultaneous active state on
PTT
and Rx carrier signal of “J0102-Main”,
which possibly causes unwanted tie condition of keying of both radios.
Accessory D-SUB 15pin receptacle (“J0103-Acc”)
The accessory D-Sub, “J0103-ACC”, is connected to “J0102-Main” and “J0104-Slave” to supply Rx
audio and
PTT
for linked radios (repeaters) or external controllers. Rx audio and
PTT
activation from the
linked facilities are applied to the repeater for transmission.
Display Unit (U0110, PB01-PB06, K02, Q0113 and Q0118)
All the functional triggers of enable and disable come from keypad PB01 to PB06. K02 is an encoder
switch for front speaker audio output adjustment. A high output from pin37 of CPU U0110 will turn on
Q0119, driving the base of Q0118 to go low. The backlight LEDs for the keypad, CR0107, CR0108,
CR0111-CR0114 illuminate. Another backlight driver, Q0113, is controlled by Q0114 through the output
from pin17 of U0110.
Peripheral Circuitry (U0108, U0109, KR00 and KR03)
Operating power bus for all the electronics originates from the switch power 13.8Vdc output, pin9 of
“J0107-Slave”, and goes through U0109 and U0108 to obtain the reference voltages of 9Vdc and 5Vdc.
KR00 is a DPDT relay driven by transistor Q0123. The output from pin25 of U0110 will turn on/off Q0123,
which activates relay KR00 to toggle the front speaker audio routes from slave radio or from master radio.
KR03 is another SPDT relay for audio test requirement. A high DC level output from pin26 of U0110 will
turn on Q0124 and key relay KR03. The Rx audio to the speaker is blocked and routed only to pin8 of the
front RJ45 connector J0109.
IMPORTANT NOTE
It is less possible to open squelch with CTCSS/CDCSS, but the
CTCSS codes near 100Hz and 150Hz have a high false opening
probability due to 50Hz AC power harmonics. Countries having
60Hz AC power may have false opening on 120Hz and 180Hz.
CTCSS code 254.1Hz has a high probability of squelch tails.
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