On Screen Manager (Osm); Self Test - NEC MultiSync FP1370 Service Manual

5) On Screen Manager (OSM)

The OSM circuit consists of IC791 (OSM controller) and IC711 (Pre-amp) which matrix the video signal and
the OSM signal. IC791 receives the display data from IC801 (CPU), and the signal outputs R, G, B and
Blanking are fed out of pins 13, 15, 17 and 12 respectively. The OSM signals are mixed with video signals in
IC711 (Pre-amp). The OSM screen brightness is controlled by I
IC801
CPU

6) Self Test

There are two ways to activate the self test function,.
User mode: power on the monitor while holding down the RESET switch
Factory mode: no H/C sync and SOG of selected input mode
When the self test mode is activated, IC801(CPU) controls IC501 to oscillate at approx.61.6KHz. Thus the
horizontal deflection circuit and the high voltage circuit operate at this frequency. When Q797 is turned off by
S_BIAS signal from IC801(CPU). The pseudo vertical sync signal count down from the horizontal sync signal
with IC8M1 is effective, and the shape AFC pulse are fed to IC791 and IC7A1, the clamp pulse for IC711 is
generated by IC7A1. The video signal is generated by IC791, and fed to IC721(Output amp) via IC711(PRE-AMP).
13
G
15
2
I C
OSM CONTROLLER
(Fig 1.5) On Screen Manager
IC7A1
M52347FP
CLAMP
I/F
PULSE
2
I CBUS
IC801
CPU
S_BIAS
(Fig1.6) Self Test
2
C BUS from CPU.
IC711
M52742ASP
PRE-AMP
9 4 1
R
B BLK
13 17 12
18
IC791
M35070-050FP
19
IC711
R/G/B
M52742ASP
PRE-AMP
R/G/B/BLK
AFC(TTL)
IC791
M35070-050FP
V(PUMP)
OSM
IC501
HE6-0092
DSP(OSC IC)
VD_SELF
IC8M1
BU6483K
AUTO SIZE
8-6
H.Sync (AFC_T)
V.Sync (VD_B)
IC721
VPS16
OUTPUT-AMP
DEFLECTION
CIRCUIT