56
6. SMALL SIGNAL PANEL
MG5.1E
6.9 The HOP High-end Output Processor
Personal notes
Figure 6-20
CL 86532047_030.eps
061098
TIME
150msec
16
µ
sec;
δ; 50%
TON
TIME
DRIVE
SIGNAL
15kV
0
VEHT [kV]
32
15
START HOP
SLOW
START
LINESTAGE
∼∼
All geometry control is done via I2C and the data is stored in the
NVM (IC7008) of the SSP.
Line drive is derived from an internal VCO of 13.75 MHz. As a
reference an external resonator is used of 12 MHz (1305). The
internal VCO is locked with the HD-pulse which comes from the
PICNIC. The PHI-2 part in the HOP receives the HFB (pin 13)
to correct the phase of the line drive. The EHT-info is supplied
to pin 14 to compensate picture breathing depending on the
beam current. (This is not used at the moment, therefore EHT-
compensation in the service menu is put to zero)<--Service tip
Picture breathing is compensated via the east/west circuitry.
EHT varies also dependent of the beam current. For
widescreen without load this is 31,5 kV and with load (1,5mA)
29,5 kV. On pin 9 the VFB comes in. If the VFB disappears, or
takes longer then the sandcastle (SC) blanking, then the picture
will be blanked (intern) by lifting the DC-level of the SC. The
SC-signal is available for pin 9 of the TOPIC.
Slow-start (fig 6-20) is realised in the start/stop part of the HOP
(pin 5/29). The horizontal drive starts with a very short ‘on’-time.
The start-frequency is 2 times higher as the normal drive-
frequency. The HOP also takes care of the slow-stop (fig 6-21).
If the HOP is put to Standby then it takes 42 msec to reduce the
T_on to zero.