Telex MCE325 User Manual download pdf (Page 41)

4-3

4 Measure the ripple.

ripple

= 140 mVp-p

5 Measure the regulated DC voltage at U26 pin 2. (There should be no ripple.)

U26-2

= 13.85 ±0.3 VDC

6 Measure the mid-voltage source at U17 pin 7.

U17-7

= 6.93 ±0.3 VDC

7 Measure the +5 V source at the output of U27 pin 2.

U27-2

= 5.0 ±0.3 VDC

Initial Configuration

1 Set all internal jumpers and DIP switches as follows:

DIP Switches: Set all DIP switches, except DS3, to the default settings listed in Table 2.1. Set

DS3 to on. (This places the MCE325 in four-channel mode. Refer to Figure 1.11 for names of

buttons in standard four-channel mode.)

Jumpers: Set all jumpers, except J24, to the default settings listed in Table 2.2. Set J24 to the

balanced mic position (pins 1 and 2 shorted).

2 Connect a 200-ohm termination resistor across each of the four intercom channels:

CH 1: J8 pins 1 and 2

CH 2: J8 pins 1 and 3

CH 3: J10 pins 1 and 2

CH 4: J10 pins 1 and 3

3 Set all front panel buttons to off.

4 Set all volume controls to minimum.

Keying Output Test

1 Connect two 47 k ohm resistors: one from the key 1 output (J22 pin 6) to the +14 VDC supply;

and one from the key 2 output (J22 pin 19) to the +14 VDC supply.

NOTE

The cathode of D22 serves as a convenient connection point for the +14 VDC supply. (Refer to

the AS6245 drawing in Section 6 for the location of D22.) The key 1 and key 2 outputs require

external pull-up resistors. The key 3 and key 4 outputs have internal pull-up resistors (RP2B

and RP2D respectively) and do not require external pull-ups.

Figure 4.1

Auxiliary connector, J22.

1 2 ... 36 37 38 39 40 41 42 43 44 45 46 ... 84 85

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Telex MCE325 User Manual Page 41