HP 8559A SW l TCH, @SWEEPDEAD, FastlSlowSweep Time Operation

MODEL 8559A SERVICE

	@SWEEP DEAD
SW l TCH	6 & I7	TIME SWITCH

I I

FIGURE8-35. SIMPLIFIED SCHEMATICOF FASTISLOWSWEEP TIME OPERATION

FastlSlowSweep Time Operation

Timing capacitors C3 and C4 provide fast and slow sweep operation (refer to Figure 8-35). When a sweep time less than or equal to 1 millisecond per division is selected with the SWEEP TIME/DIV switch, sweep control line ST6 is grounded. This turns sweep dead time switch 4 6 (block K) and fast sweep switch 4 7 (block J) off. With 4 7 off, C3 and C4 are in series; C4 effectively becomes the timing capacitor. With 4 6 off, +15V at R46 reverse biases CR9 and CR8, switching C10 out of the dead time circuit. Capacitor C11 now sets a short dead time of about 0.4 millisecond.

In sweep times greater than or equal to 1 millisecond per division or in automatic sweep, control line ST6 is open, turning both Q6 and 4 7 on. Transistor 4 7 grounds C3 and it becomes the timing capacitor. Transistor 46 forward biases CR8 and CR9, paralleling C10 and C11. The dead time is effectively established by C10 at about 8.0 milliseconds.