McIntosh MAC1500 - SERVICE 1 User Manual download pdf (Page 6)

DECODER ALIGNMENT

ADJUST

67KC Trap (L-6)

T-6 top and

bottom;

L-5

T-7 bottom core

T-7 top core

L-5

MPX light adjust

control R-12

TEST

LIMITS

Adjust for mini-

mum voltage

Adjust for maxi-

mum voltage

SAME

Adjust for stable

scope display

30db separation

or more

SAME

REMARKS

Stereo light must be on. This is done by adjusting the "MPX Light

control, R-12.

Adj."

Stereo light must be off.

• ~

Stereo light must be completely on.

1. Turn off 19KC pilot on MPX generator.

2. Adjust upper core of T-7 to obtain a stable and uniform 1 KC signal

scope display. This adjustment may be critical, so turn core very

slowly.

3. Turn 19KC pilot back on.

Modulate left channel and measure right channel output. Adjust L-5 for

minimum right channel output (maximum separation). Be sure all test

leads are removed from TP#2 for separation tests.

Modulate right channel and measure left channel output. Separation in

steps 5 and 6 should be at least 30db.

This step checks the rejection of 19KC and 38KC frequencies. Residual output should be

at least 40db below modulated output.

Turn control until light comes on. Then back off just enough to cause

the light to go off. Then back off about 1/8 of a turn more. Light should

operate ONLY on a MPX signal.

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McIntosh MAC1500 - SERVICE 1 User Manual Page 6

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