Cut Off Control - Loewe Q2500B Serviceanleitung

Technology of Q 2500 colour TV set
R3181
C3202
R3356
U12
URef 2,4V
U12
R3352
R3353
For control of the c.r.t. cathodes the signals
are applied at a maximum 160 Vss via pin 7
and 8. Control is via pin 8 with a corrective
signal on pin 7, in order to achieve an auto-
matic blanking current control. The emitter
follower on the output of the output stage
permits rapid blocking of the cathodes on
transition from bright to blank. This permits the
delaying effects that are otherwise present to
be reduced.
The IC's also contain a component for tem-
perature drift compensation, as well as a cir-
cuit via which the transient current can be de-
coupled. Current information is taken from pin
5, and so with an additional sensor control
circuit an automatic blanking value control (cut
off control) can be established.
Document Q 2500
Colour output
U12
C3181
R3391 R3393 R3348
Q3181
L3393
L3392
R3186
C3392 C3398 C3399
R3380
C3352 C3374
C3394
Switch off flash
suppression
D3391
R3397
Q3396
U12 U200
C3393
C3397
-
I 3391
+
Grün

2.9.1 Cut off control

The cut off control is basically a sensor control
circuit. It controls electronically dynamic com-
ponent tolerances and signs of wear, e.g. of
the c.r.t.s.
It also has the following advantages:
− automatic blanking value equalisation.
− Avoidance of colour distortion during c.r.t.
warm up time and control of above average
ageing in the initial operating hours.
38
Uf
R3392
10
8
R R
R3398
L3398
6
G
11
B B
12
4
9
R3394
C3368
R3368
R3362
D3367
C3367
R3367
C3360
© Loewe ProCollege
V3001
5 7
29kV