MCINTOSH MAC 150
Service Manual

DECODER ALIGNMENT
TEST LIMITS Adjust for minimum voltage

ADJUST

REMARKS

67KC Trap (L-6)

Stereo light must be on. This is done by adjusting the "MPX Light Adj." control, R-12.

T-6 top and bottom; L-5

Adjust for maximum voltage

Stereo light must be off.

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T-7 bottom core

SAME

Stereo light must be completely on.

T-7 top core

Adjust for stable scope display

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.

L-5

30db separation or more SAME

This step checks the rejection of 19KC and 38KC frequencies. Residual output should be at least 40db below modulated output. MPX light adjust control R-12 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.

5