MG5.1E
6. SMALL SIGNAL PANEL
57
6.9 The HOP High-end Output Processor
Figure 6-21
CL 86532047_031.eps
061098
42ms
38ms
32
15
STOP HOP
32kV
SLOW
STOP
LINESTAGE
VEHT [kV]
TIME
16
µ
sec (
δ; 50%)
TON
TIME
DRIVE
SIGNAL
0
TIME
∼∼
Protections/detections:
•
Flash detection (see figure 6-25). When a flash occurs, the
EHT-info will become negative very fast. Via D6340/6341
TS7341 starts to conduct. This makes pin 5 of HOP high.
When pin 5 of HOP is high then the output (Hdrive) is
immediate stopped. If H-drive stops then also pin 5 will be
low again, which will reset the flash detection. A bit (FLS)
will be set in an output status register, so via the
microprocessor it can be seen when there was a flash. This
FLS-bit will be reset when the microprocessor has read that
register.
•
Beam current protection. Via D6350 and TS7351. If the
EHT-info becomes too low then D6350/TS7351 will start to
conduct making the BC-prot high. The BC-prot is sent to the
microprocessor who puts the TV into protection mode with
a delay of 1 sec. An error code will be generated.
•
Line drive protection (LDP) The current through the east/
west stage is measured. When this becomes too high then
the protection has to be activated. Therefore the protection
is fed back to pin 5 of the HOP. If LDP is activated the FLS-
bit will also be set but the software can detect whether is
was a flash or a protection. In this case the FLS-bit will
remain high and the set goes into protection. An error code
will be generated.
•
HFB protection If the HFB is not present then this is
detected via the HOP. The microprocessor puts the TV into
protection and reads a register in the HOP. An error code
will be generated.
•
VFB protection If vertical flyback is missing or if the VFB
takes longer than the V-blanking of the sandcastle, than the
picture will be blanked and there is also a bit set in the HOP.
The microprocessor detects this and puts the TV into
protection. An error code will be generated.
The vertical oscillator is synchronised with the VD from the
PICNIC. With R3323 the positive slope of the charge current is
set, with C2323 the negative ramp of the current. The outputs
(pins 1 / 2) are differential voltages Vdpos and Vdneg. These
create differential currents which are fed to the vertical output
stage. At pin 3 the E/W-drive is available. Pin 4 is a feedback
input for the EHT-info. Depending on the beam current the
vertical and horizontal deflection is kept constant to prevent
pumping of the picture.
Frame rotation (only for 16:9 sets): For frame rotation a control
voltage is used from pin 25 of the HOP. This voltage can vary
from 0.4V till 4V.