Read Sharp 76FW-53H (serv.man13) Service Manual online
Colour Television – DA100/DW100 Chassis
Sharp Electronics (UK) Ltd
Technical Support
September 99
Page 20
V
IDEO
/S
YNC
P
ROCESSOR
The video/sync processor (IC801) contains protection circuit that can monitor the scanning circuits
operation.
operation.
S
AFETY
IC801 pin 12, EHT is calculated by measuring the rectified horizontal fly-back pulse. D615 and C617
are the rectifier components, and D617 limits the bias at pin 12 (sets normal conditions, >1v) There
are two thresholds once the first threshold has been met the RGB drives are blanked, if the d.c.
voltage continues to rise and passes the second threshold, then the horizontal drive is stopped.
are the rectifier components, and D617 limits the bias at pin 12 (sets normal conditions, >1v) There
are two thresholds once the first threshold has been met the RGB drives are blanked, if the d.c.
voltage continues to rise and passes the second threshold, then the horizontal drive is stopped.
V
PROT
This pin is monitoring the operation of the vertical output stage. The vertical fly-back pulses are
applied to pin 11. If the negative edge of this signal cannot be detected then the RGB drives are
blanked.
applied to pin 11. If the negative edge of this signal cannot be detected then the RGB drives are
blanked.
+5v
Q608
Safety
HFB
HFB
D618
4v7
4v7
C643
10nF
10nF
R644
220
220
C617
100nF
100nF
D617
24v
24v
D615
R615
1k
1k
R620
1k
1k
IC801
12
13
11
Vprot
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