(G) Overvoltage Protection; (H) Auto And Manual Degaussing Circuit - NEC MultiSync 4FGe Service Manual

(g)
Overvoltage Protection
If a failure occurs and the output voltage on the secondary winding rises, the voltages of the auxiliary
winding will also rise proportionally. When the auxiliary windings voltage rises beyond the zener voltage of
ZD604, CR602 will turn ON. This in turn will decrease the voltages at pinaof IC601 causing the oscillator
within IC601 to stop.
CR602
A
K

(h) Auto and Manual Degaussing circuit

1) Auto Degaussing Circuit
When the unit is turned ON. The +24V DC output at k3 rises. This will cause 0671 to turn ON. The ON
period for this transistor is determined by R673, ZD671, R674, and C671 (approx. 2 seconds). When 0671
is ON, current will flow through the Degaussing Coil
2) Manual Degaussing Circuit
When the Degauss Switch is turned ON, 0673 conducts thereby discharging C671, When C671 is
discharged, Q671 will turn on again.
TH601
Degaussing
Coi I
R605
R610
C621
(Fig 2-l -7) Over Voltage Protection
(Fig l-l -8) Auto and Manual Degaussing Circuit
39
D608
0615
C603 +
-
T601
Manua I
Degaussrng