Mitsubishi Electronics WS-48613, WS-65513, WS-48513, WS-55513 manual Deflection Loss Detection

The DEFL-MUTE line from the µPC and Q5A08 reduce the DC supply during scan frequency change by the same method.

The DC supply for the Horizontal Drive transistor, Q5A32, is derived from the Horizontal Output DC supply through R5A36, R5A37 and Q5A34. In the

31.5kHz mode, the DC supply for Q5A32 would drop, since the supply for Q5A31 decreases.

To prevent this the 31K control line also connects to the base of Q5A35. When Q5A35 is driven into conduction, the conduction of Q5A34 is increased to maintain the DC supply for Q5A32.

Deflection Loss Detection

To prevent damage to the CRTs, the TV must shut Off if deflection is lost. The Deflection Loss Detec- tion circuit is similar to previous models, as shown in Figure 6-7.

Q4B01 monitors vertical deflection, and Q5A38 monitors horizontal deflection. The conduction of both transistors holds their respective collector volt- age below the forward bias point of the diode in their collector circuit's (D4B04 or D5A12).

If either Q4B01 or Q5A38 stop conducting, indicat- ing a loss of deflection, the increase in that transistor’s collector voltage drives the V-Blank line High. The V-Blank line goes to the CRT Protect circuitry and immediately removing all drive to the CRTs.

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