Viking VX 900 MHz LTR User Manual page 73

OCXO 1 BUFFER
Y901
REMOTE SWITCH REMOTE SWITCH
S904
CR902/CR903 S904
U908
OCXO SWITCH OCXO SWITCH
S905
CR904/CR905 S905
U909
OCXO 2 BUFFER
Y902
FRONT PANEL
SWITCH CONTROLS
OCXO 2
TEST
S902
OCXO 1
TEST
S901
DC ON/OFF
S903
The OCXO drawer may be powered by the inter-
nal regulated 15V DC supply, or by an external 15V
DC source. The internal 15V DC supply is powered
from a 120V (±10%) or 240V (±10%) AC line. When
both supplies are present, the internal 15V DC supply
powers the drawer and the external 15V DC supply is
a backup. If the internal supply should fail, the exter-
nal 15V DC supply powers the drawer. The current
requirement of the drawer is less than 1A upon initial
turn on, and reduces to approximately 630 mA after
the oscillators are stabilized.
SWITCH
(OSC 1)
Q901
(OSC 2)
U901A/B/C/D,
U902B, U904D
SWITCH
U901A/C/D
U903D, U904A
Q902
U910A
FLIP-FLOP
VCO/PHASE
COMPARATOR
DC ALARM
INDICATOR
Q917, DS905
FAIL STROBE
U914A, Q916
AC ALARM
INDICATOR
Q912, DS906
U914D, Q921
Figure 6-5 OCXO DRAWER BLOCK DIAGRAM
U906A
DIVIDER
U905 LINE DRIVERS
U906B
ONE-SHOT OCXO RF OUTPUT
MULTIVIBRATOR ALARM INDICATOR
U907
STROBE CLOCK
U904B/C/D
ALARM INDICATOR
ONE-SHOT
MULTIVIBRATOR
U911
U913
U910B
FLIP-FLOP
The OCXO drawer contains several alarms. For
all alarms, the following color scheme applies (see
Figure 6-6):
Flashing Red
Yellow
Green
If the main oscillator fails, its corresponding LED
turns from green (active) to flashing red (failure).
Consequently the LED for the remaining oscillator
changes from yellow (standby) to green (active).
6-13
CIRCUIT DESCRIPTION
10 MHz REF OUT
1.25 MHz REF OUT
ALARM RELAY
Q905, K901 RF ALARM OUT
Q903, DS901
U902C, Q904
ALARM RELAY
Q908, K902 OCXO 1 ALARM
OCXO 1
Q906, DS902
U903C, U912A
Q907
ALARM RELAY
Q911, K903
OCXO 2
ALARM INDICATOR
Q909, DS903
U903A, U912B
Q910
ALARM RELAY
Q914, K904
DELTA F
ALARM INDICATOR
Q912, DS904
U914B, Q913
ALARM RELAY
Q918, Q919
Q920, K905
ALARM RELAY
Q923, Q924
Q920, K906
Failure
Standby
Active (OK)
Part No. 001-2009-201
OCXO 2 ALARM
DELTA F
DC ALARM
AC ALARM
October 1999