1-Second-Delay Circuit - HP 6033A series Service Manual

1-Second-Delay Circuit

The 1-second-delay circuit is the heart of the unit's controlled turn on. It causes relay A1K1 to bypass inrush
current-limiting resistor A1R1 one second after turn on, and it enables the PWM 0.1 second later. When either the output of
the ac-surge-&-dropout detector or PCLR2 is low NAND gate A2U11A holds the circuit reset. The circuit starts counting
at 1/16 the clock frequency (1.25 KHz) when both inputs to A2U11A are high and causes RELAY ENABLE to go high in
1.0 seconds and DROPOUT to go high in 1.1 seconds. When DROPOUT goes high, it stops the count, and it enables the
PWM.
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