SRS Labs SR560 manual Batteries And P.E.M, Front Panel, Circuit Description

CIRCUIT DESCRIPTION

BATTERIES AND P.E.M.

The batteries used in the SR560 are of sealed lead-acid construction. There are three 12 V, 1.9 amp-hour batteries, two of which serve as the positive power supply, and one of which serves as the negative power supply. Powering the SR560 alone, battery life should be greater than 20 hours. The batteries should last for more than 1000 charge / discharge cycles, provided the guidelines under the Usage section are followed. Two 3A, fast blow fuses on the rear panel protect the battery supplies and amplifier against excessive currents.

The power entry module (P.E.M.) contains the AC line fuse, RFI filter, and voltage selection card. To change the operating voltage of the unit, the voltage selector printed circuit card must be pulled out and reinserted into the P.E.M. with the desired operating voltage visible.

FRONT PANEL

The front panel contains the keypad pushbuttons, LED indicators and serial shift registers. The front panel pushbuttons are decoded in a 3 x 4 matrix fashion. The front panel LEDs are controlled by shift registers U1 through U5, which allow the 5 eight-bit control bytes to be serially shifted-in one bit at a time. The red overload LED is controlled directly from the output of the overload comparator.

The battery LED is a dual-color LED that is green when the unit is operating on battery power, and turns red when the low_batt signal is asserted.

The front panel output offset pot P1 is also mounted on the front panel printed circuit board.

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