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Serviceman Mode (Electronic Controls, Cont.)
Stereo Separation Adjustment (M3 & M4)
2. Adjust M3 (MTS Low-Level Separation) data
(in the
Preparation:
Serviceman Adjustment Menu)
until the amplitude of
the measured waveform on the scope is minimum.
Connect an RF signal generator
the RF
3. Apply
the
following
signal
from
the
RF
antenna input.
signal generator:
2. Connect an oscilloscope probe to TPEI 0 and GND
wire to TPA13 (GND).
Video: 100 IRE flat field, 30% modulation.
Procedure:
Audio: 3KHz, 30% modulation, stereo (left only).
1.
Apply the following signal from the RF signal
(70dB
*
5dB, 75R OPEIV, P/S 1 OdB).
generator:
4. Adjust M4 (MTS High-Level Separation) data
(in the
Serviceman Adjustment Menu)
until the amplitude of
Video: 100 IRE flat field, 30% modulation.
the waveform measured on the scope is minimum.
300Hz, 30% modulation, stereo (left only)
5. Repeat above steps 2 through 4 until the amplitude
(70dB
+
5dB, 75R OPEN).
is at minimum for both signals.
Note: Set Audio mode to Stereo.
Serviceman Mode (Mechanical Controls)
2nd Tuner
-
VCO Adjustment, Mechanical
(S-Board)
Note: Allow 20 seconds of aging prior to making the
flowing adjustments.
Preparation:
1. Apply color bars to the video input.
2. Connect an oscilloscope to TP12 (on S-Board).
Use cold ground for scope connection. Set the
scope at Horizontal Sweep rate ( 2 0 ~ s ) time base.
3. Connect a DVM to TPlO (on S-Board).
4. Connect a jumper between TPA7 and TPA13
(GND) on the A-Board.
Procedure:
1. Adjust L2109 (on S-Board) to measure 2.4Vf 0.1V
on the DVM. Confirm that the scope reading is
within 1.0 f 0.25Vp-p from sync tip to white level.
See Figure 31
C
Figure 31. TP12 Waveform
2nd Tuner
-
RF-AGC Adjustment,
Mechanical
(S-Board)
Preparation:
1. Connect a DVM to 2nd tuner AGC terminal.
2. Apply color bar with 63f2dB (75R open).
Procedure:
1. Rotate R2118 (on S-Board) fully clockwise and
confirm that
noise disappears. Record the
reference voltage.
2. Rotate R2118 fully counter-clockwise and confirm
that noise appears.
3. Slowly turn R2118 clockwise until the reference
voltage is obtained.
4. Confirm RF-AGC voltage (the reference voltage) is
lower when the incoming field signal strength is
increased by 3dB.
2. Check that the sync signal amplitude (ratio
between the sync signal to detection output) is
within the range of 30 f 5 % (S/(S+P)
=
30 f5%).
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