Voltage Selection, Diode Isolation of Logic Controls

Diode Isolation of Logic Controls

Two or more control functions using the same logic pins can be isolated with diodes. In this manner a channel can be muted by an overall group mute switch, or by its own cough button (see Figure 19-Channels 1, 3 and 5 modified).

D = 1N4148 OR

GROUP EQUIVALENT

MUTE

Mixer logic may be used with 15-volt CMOS logic if a pull-up resistor is used with each GATE output (see Figure 20-Channel 1 modified).

	5.1 K	15 V
	5.1 K	POWER
		POWER
		SUPPLY

–

M1 M3 M5

COUGH

BUTTONS

LOGIC

GROUND

CMOS

GATES

LOGIC

GROUND

G1 M1

DIODE ISOLATION OF LOGIC CONTROLS

FIGURE 19

External Logic Devices

SCM810 logic levels are directly compatible with TTL and 5-volt CMOS log- ic families. For information on logic gate use, refer to the TTL Cookbook and CMOS Cookbook, both by D. Lancaster, Howard Sams Publishing Co.

15-VOLT CMOS

FIGURE 20

Digital Controls or Microcomputers

The SCM810 logic pins can interface with custom-designed digital control circuitry or microcomputers for unlimited possibilities of system control functions.

VOLTAGE SELECTION

The SCM810 can be internally modified to operate from 230 Vac, 50/60 Hz power.

WARNING: Voltages in this equipment are hazardous to life. No user-serviceable parts inside. Refer all servicing to qualified service personnel. The safety certifications of the SCM810 do not apply when the operating voltage is changed from the factory setting.

To change the operating voltage, follow these steps.

1.Disconnect the SCM810 from the AC power source.

2.Remove the eight Phillips head screws securing the top cover.

3.Locate Voltage Selector switch SW903 adjacent to power transformer T901 and, using a screwdriver, turn the center rotor to the 230 V posi- tion.

4.Locate Fuse F901 and remove it. Replace it with a 100 mA, 250 V, time delay fuse for 230-volt operation (200 mA, 250 V, slow-blow fuse for 120-volt operation).

Fuse part numbers are:

Fuse Type	Shure Part No.	Whitefishes Part
		No.

100 mA, 250 V	80C258	218.100

200 mA, 250 V	80BC8196	239.200

5.Replace the power cord with a cord rated for 230 V operation, i.e., an IEC appliance connector on the equipment end and a CEE 7/7 (“Schuko”) mains connector on the other.*

Similarly, the SCM810E can be internally modified to operate from 120 Vac, 50/60 Hz power.

*For systems requiring other mains connectors, obtain a power cord with an IEC 320 type mating connector for connection to the SCM810, and an appropriate plug on the other end for connection to the mains. The supplied cord uses Harmonized IEC Cordage with color coding as follows: Brown = Line, Blue = Neutral, Green/Yellow = Ground