Horizontal Amplitude Control - NEC MultiSync FE700 Serviceanleitung

7. Horizontal amplitude control

Circuit Diagram
Q1
Description of the circuit:
4) The diodes D1 and D2 compose the bipolar modulation circuit, and have the function of controlling
the currents of the coils DY(Ipp) and Lm(Im) through voltage modulation carried out by utilizing Vm.
B+ = Vm +Vcs
Such being the case, the horizontal width decreases when Vm ↑ ↑ ↑ ↑ → Vcs ↓ ↓ ↓ ↓ → Iy ↓ ↓ ↓ ↓
Inversely, the horizontal width decreases when Vm ↓ ↓ ↓ ↓ → Vcs ↑ ↑ ↑ ↑ → Iy ↑ ↑ ↑ ↑
(B+ = (Vp*2Tr)/(π π π π *Ts), Tr = √LyCt, Tm = √LmCm)
5) Q2, Q3 and Q4 compose the control circuit of H-WIDTH. Of those devices, the transistor Q2 and Q3
compose the Darlington current amplifier, and on the other hand the transistor Q4 and the operational
amplifier U1 compose the emitter-coupled circuit, that stabilize the voltage and control the current.
6) The horizontal width broadens when Va ↑ ↑ ↑ ↑ → → → → Vm ↓ ↓ ↓ ↓ . An inference in the opposite sense is also
possible.
B+
DY
CT
D1
CS
Lm
Cm
D2
Csm
Therefore, Vcs = (Iy * Ly)/ts → → → → Iy = (Vcs * ts)/Ly, with B+ fixed.
R6
Q2
Q3
Q4
R3
Vm
8 - 25
B+
AC PIN
C1 R1
R5
R2
H-Width
R7
Va
R4
DC