Service Mode; Video Text; Picture Signal Processing - Loewe Q2500B Serviceanleitung

Technology of Q 2500 colour TV set
Changes to these values will be communi-
cated via the I²C bus to the appropriate proc-
essors during the adjustment procedure and
can then be adjusted to the required values.
All data read in on start up as well as data
changed by the customer during operation, is
checked during operation by continuous
communication between the SDA 6000 and
the signal processors. If deviations occur
these are corrected immediately.
This is particularly the
dependent tuning values such as, for exam-
ple, white value, black value and c.r.t. leak-
age current. For this reason in devices incor-
porating the Q 2500 chassis, ageing of, for
example, the c.r.t. only becomes apparent
when the scope of control is exhausted and
the c.r.t. is totally worn out. In our chassis
these dynamic tuning values are therefore
subject to special treatment. The values for
these functions held in the memory are auto-
matically updated to the current values on
each save procedure. In this way updating of
the current wear-determined values on start
up is not necessary, which the end user will
surely notice.
For control and adjustment procedures via the
remote control and local operating buttons the
changes are initially made only in the working
memories of the appropriate IC's and in the
register of the SDA 6000. Normally the saving
of values in EAROM must be implemented by
an additional command (usually the OK but-
ton). If the remote control is used to switch the
device to standby, then the data in the register
of the SDA 6000 is available when the unit is
restarted. The data within the unit, such as the
last volume level set is retained.
When the unit is switched off at the mains the
microprocessor register is deleted, and on the
next start up only the EAROM data is avail-
able. So that specific settings are retained, the
EAROM has an area for "Last memory" data.
On shut down the data is saved to this area
(e.g. last programme location). In addition, a
few seconds after programme location change
the set programme location is saved in the
Last Memory data area.
Document Q 2500
case for time-
78

4.2.10 Service mode

In order to carry out chassis tuning the device
must be placed in the required service mode.
The remote control can then be used to call
up all the necessary functions for chassis tun-
ing, with a few exceptions. After successful
tuning the new values must be saved.
The exact functions available in the service
mode can be found in the service instructions
for the appropriate device.

4.2.11 Video text

In the 100Hz TV set system the videotext
function and the production of overwriting
OSD is now the responsibility of the CCU SDA
6000.
For this reason the FBAS signal is fed to pin
117 of the CCU. The CCU controls full data
separation and memory administration inter-
nally. The VT pages are then stored in the
SDRAM I 2916.
The VT information as also the OSD overwrit-
ing are applied to pins 112/113/114 of the
CCU as RGB signals.

4.2.12 Picture signal processing

Picture signal processing is implemented by
highly integrated modern circuits that have
been used for the first time by Loewe, in simi-
lar IC variants, in the Q 2300 chassis genera-
tion. The highly integrated IC's mean that for
the two 100 Hz generation chassis Q 2100
and 2200, the 100 Hz module necessary for
the signal board can be dispensed with. All
the ICs necessary for signal generation can
be fitted without problem on the component
side of the signal board. This also provides
much simpler faultfinding, which is also fa-
voured by the clear signal flow.
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