Guide Roller Height Adjustment; Preliminary Adjustment; Precise Adjustment - Zenith ABV341 Series Service Manual

DECK MECHANISM ADJUSTMENT

4.Guide Roller Height Adjustment

Purpose: To regulate the Height of the Tape so that the Bottom of the Tape runs along the
Tape Guide Line on the Lower Drum.

4-1. Preliminary Adjustment

Test Equipment/ Fixture
• Post Height Adjusting Driver
Adjustment Procedure
1) Confirm that the Tape runs along the Tape Guide Line of the
Lower Drum.
2) If the Tape runs at the Bottom of the Guide Line, turn the
Guide Roller Height Adjustment Screw Clockwise.
3) If it runs at the Top, turn Counterclockwise.
4) Adjust the Height of the Guide Roller to be guided to the
Guide Line of the Lower Drum from the Starting and Ending
Point of the Drum.

4-2. Precise Adjustment

Test Equipment/Fixture
• Oscilloscope
• Alignment Tape
• Post Height Adjusting
Driver
Adjustment Procedure
1) Play an Alignment Tape after connecting the Probe of the
Oscilloscope to the RF Envelope Output Test Point and
Head Switching Output Test Point.
2) Tracking Control (in PB Mode): Center Position (When
this Adjustment is performed after the Drum Assembly
has been replaced, set the Tracking Control so that the
RF Output is Maximum).
3) Height Adjustment Screw: Flatten the RF Waveform.
(Fig. C-4-2)
4) Turn (Move) the Tracking Control (in PB Mode)
Clockwise and Counterclockwise. (Fig. C-4-3)
5) Check that any Drop of RF Output is uniform at the
Start and End of the Waveform.
NOTE
If the adjustment is excessive or insufficient the tape
will jam or fold.
Test Conditions (Mechanism Condition)
• Play or Review Mode
Test Equipment Connection Points
• CH-1:PB RF Envelope
• CH-2:NTSC: SW 30Hz
PAL: SW 25Hz
• Head Switching Output
Point
• RF Envelope Output
Point
• Guide Roller Height Adjustment
screws on the Supply and Take-Up
Guide Rollers.
ADJUSTMENT DIAGRAM
Test Conditions VCR (VCP) State
• Play an Alignment Tape
Waveform Diagrams
P2 POST
ADJUSTMENT
P3 POST
ADJUSTMENT
Tracking control at center
Connection Diagram
RF ENVELOPE OUTPUT TEST POINT
HEAD SWITCHING OUTPUT TEST
POINT
4-15
Adjustment Point
Guide Roller Height
Adjustment screw
Upper Flange
Guide Roller
Retaining Screw
Fig. C-4-1
Adjustment Point
• Guide Roller Height
Adjustment Screws
Turn the Roller Guide Height
Adjustment Screw slightly
to flatten the waveform.
Fig. C-4-2
Turn (Move) the tracking
control to both directions
Fig. C-4-3
OSCILLOSCOPE