Vertical Protection - Hitachi C1422R Service Manual

Vertical Protection

When operating normally, the vertical output stage generates a +5.5V pulse during vertical flyback blanking.
This pulse is fed via Q407 to I501 beam current input. Should this pulse fail, the picture tube outputs are
"blanked off" until after about 12 seconds, the micro controller records a failure. For diagnostic purposes,
vertical protection during the 12 second interval may be disabled by pressing the '2' key on the remote
control handunit when in service parameter 'OA'. This should always be re-enabled after repair (See
adjustments section).
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