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Operation Theory
CPQ-C1786FNSL/T (FS7550/V7550)
4-3 Deflection Section
1. I
2
C -- autosync deflection controller is TDA4841.
2. The TDA4841 is a high performance and efficient solution for autosync monitors. All functions are
controllable by I
2
C bus. SDA and SCL signals coming from microprocessor feed to pin 19 and pin 18 to
control all functions.
4-3-1 Horizontal Section
1. The oscillator is driven by the currents in R419 and R420. The minimum oscillator frequency is determined
by R419 and the maximum frequency is determined by R420.
2. Horizontal sync goes into pin 15 through R318. And horizontal flyback pulse goes into pin 1 through R401
and bypass filter C403 from pin 5 of FBT and R496 for HFLB loop.
3. Horizontal driver (pin8) O/P to Q401 via C410.
4-3-2 Vertical Section
1. Vertical sync goes into pin 14 through R317.
2. The free running frequency is determined by R301 and C301.
4-3-3 Vertical O/P section
1. The differential output currents from pin 13 of Vout1 and pin 12 of Vout2 can be directly coupled to the
vertical deflection booster pin 7 and pin 6 of TDA4863.
2. The TDA4863 has two output stages which are current driven in opposite phase and operate in combination
with the deflection coil in a full bridge configuration.
3. This IC is powered by two sets of positive voltage and one set of negative voltage. (+11.5V at pin 1, -12V
at pin 4, +40V at pin 2).
4-3-4 E-W/Trapezoid and H. Width Controls
1. The horizontal O/P stage uses diode modulator D419, D433, C411, C412, L409 and C418 for East-West
(Pincushion) Trapezoid and H. width controls.
2. The scan current is determined by B
+
minus Vm ( the voltage of C418) values and the pincushion control
is accomplished by Darlington pair Q418 and Q419 by coupling a parabola waveform from pin 11 of
TDA4841. The H. width / corner and trapezoid correction are also accomplished by this pin 11. The DC
level controls H. size. The AC level is combined with side pin and trapezoid corners functions.
4-3-5 X-Ray Protection
1. To avoid X-ray hazard, a DC voltage generated at pin 4 of FBT and rectified by D408, C432 and divided
by R403, R404 and R405 come into pin 2 of TDA4841.
2. If this voltage is higher than 6.39 V, then TDA4841 will be activated to float HUNLOCK (pin17), H.
DRV( pin 8), B DRV (pin 6), VOUT1 (pin 12), VOUT2 (pin13). After that all deflection circuit stop
working.
