Mitsubishi Electronics WS-55513, WS-65513, WS-48613, WS-48513 manual Ray Protect

DO NOT measure the HV-DC-FB voltage at pin 13 of the T5A51. The meter may load down the inter- nal resistive divider, resulting in excessive HV.

X-Ray Protect

X-Ray Protect circuitry is the basically the same as in previous models, as shown in Figure 5. The X- Ray Protect circuit in the V20 monitors three items:

1)Q5A51 (HV Output) current, by monitoring Q5A51 source voltage.

2)Excessive HV, by monitoring the rectified voltage from D5A57.

3)Excessive CRT Beam current, by monitoring the voltage at pin 8 for T5A51.

Each of the monitored sources is applied to an input of an OP-Amp in IC5A02. The second input of each OP-Amp is connected to a specific reference. The outputs of all three Op-Amps are tied together at the X-Ray line.

The X-Ray line is normally High. If any of the moni- tored sources exceeds its’ specific reference the X- Ray line is pulled Low, shutting Off the TV.

The connection from the source of Q5A51 to pin 5 of IC5A00 provides further protection. If the source voltage becomes excessive (excess current), IC5A00 immediately removes all drive to Q5A51.

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