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2-17

(1) Lower the main brake assemblies (S, T) until they reach to

the limit and slide the change arm assembly by the arrow,
mount them so that the positioning holes of the slide plate
match the holes on the main deck assembly.

(1)  When mounting the rotary encoder, apply the triangular po-

sitioning marks of the rotary encoder to those on the mount-
ing shaft, and insert it until the catches are locked.

(2)  When mounting the change lever, set it so that the position-

ing holes of the change lever are matched with those on the
main deck.

(3)  When mounting the control cam, while releasing the cap-

stan brake assembly by the arrow, set it so that the position-
ing holes of the control cam are matched with those on the
main deck.

(1) Mount the control plate so that the two positioning holes of

the control plate match the holes on the main deck assem-
bly and the positioning holes of the take-up lever.

(2) After mounting the control plate, secure it with the slit washer

and the control bracket.

Rotary encoder

Catch

Catch

Positioning 
mark

Positioning hole

Change lever

Positioning hole

Control cam

Capstan 
brake arm 
assembly

Main brake assembly (S)

Change arm 
assembly 

Main brake  assembly (T)

Positioning hole
(Screw is attached from 
the bottom surface.)

Lower until it reaches the end

Slide plate

Insert the boss

Match with lower holes

Control plate

So that the holes of the 
take-up lever are seen

Slit washer

2-18

2.5.1  FM waveform linearity check/adjustment
(1) Connect the oscilloscope to TP5 (PB FM: 8F) on the P/R

board assembly and connect the external sync output to TP4
(D  FF: 7F) on the P/R board assembly.

(2) Play back the alignment tape VFK1741 to observe the FM wave-

form.

(3) During playback, press the tracking buttons (+, –) simultane-

ously to enter the tracking center position.

(4) By adjusting the tracking, check that there is no apparent

level drop in the FM waveform and that the waveform var-
ies totally in parallel and with linearity.  If required, perform
the following adjustments. (Fig. 2-5-1)

(5) Using the hexagonal wrench (1.25 mm), lightly release the

set screw at the bottom of the pole base assembly.  (Pay
attention not to release too much.)  (Fig. 2-5-2)

(6) During playback, press the tracking button (+, –) to reduce

the FM waveform.  If a drop in level is observed at the left-
hand side as shown in Fig. 2-5-3, adjust the guide roller on
the pole base assembly (S) using the roller driver so that a
linear FM waveform is obtained. If a drop in level is observed
at the right-hand side, rotate the guide roller on the pole
base assembly (T) for adjustment.  (Fig. 2-5-3)

(7) After adjusting, tighten the set screw at the bottom of the pole

base assembly.  (Pay attention not to tighten excessively.)

(8) After tightening the set screw, play back the alignment tape

VFK1741 to check the FM waveform varies as shown in the
optimum waveform changing examples.

(9) When the alignment tape VFK1741 is played back after being

ejected and reloaded or soon after the search reverse mode
is operated, check that the FM waveform stabilizes within 2
sec. of appearing. If it takes more than 2 sec., check which
side (right or left) of the FM waveform is unstable and check
the following items.
A drop in level is observed at the left-hand side:

Check the guide roller (S) of the Pole base assembly

A drop in level is observed at the right-hand side:

Check the guide roller (T) of the Pole base assembly,
the height of the guide arm assembly, and the tilt of
A/C head

(10) Perform the tape transport system check. (Refer to Sec-

tion 2.5.6.)

Proper waveform variation

Max. level

Min. level 

Improper waveform variation

Roller driver

Hexdriver

Tighten

Loosen

1.25mm

SP guide roller

Pole base assembly

2-19

 • Tilt (forward bent ) adjustment
(1) Adjust the screw 

1

 with the parallel check plate so that the

tilt of the A/C head assembly is 0.05 mm.

(2) Confirm that tape is neither damaged nor wrinkled around

the lower flange of the guide roller (T). If tape is wrinkled,
fine adjust the height of the guide roller  (T). (Refer to Sec-
tion 2.5.6.)

 • Height and azimuth adjustment
(1) Connect the CH-1 of the oscilloscope to Audio Out terminal

and connect the CH-2 to TP624 (CTL: 6Q) on the main PC
board, then observe the waveform at both channels with
ALT mode.

(2) Play back the VFK1741 alignment tape, and adjust the wave-

form of Audio Out and control pulse are maximum values by
rotating the screws 

1

, 

2

 and 

3

 small and equal increments.

<Height adjustment>

(3) Then rotate the screw 

2

 to adjust so that both the audio

and control pulse waveforms become maximum. <Azimuth
adjustment>

(4) Repeat the above steps No. (2) and No. (3) alternately for

more precise adjustment.

(5) Confirm that the tilt of the A/C head assembly is 0.05 mm

with the parallel check plate. If it is out of specification, re-
peat all the steps of this section.

(6) Perform the tape transport system check. (Refer to Section

2.5.6.)

A

B

C

D

Level drop at the SP guide roller

Level drop at the TU 
guide roller

• Improper waveform variation:

• Proper waveform variation: Always flat

Higher

Lower

Parallel check 
plate

Audio out

 TP624: 6Q
( CTL )

Guide pole (T)

Lower flange

A/C head assembly 

Guide roller (T)

A/C head

OK

0.05mm

NG

NG

No rattling

Rattles on

the top

Rattles on 

the bottom 

1

2

3

• How to use the parallel check plate

1

Set the flat surface of the plate to the guide 

roller (T) and the tapered surface to the A/C 
head assembly.

2

Check if there is any rattling by pressing the top 

and bottom of the plate of the A/C head 
assembly.

A/C head should be 
bent to forward and 
the tilt should be 0.05 
mm.

1

Turn 
the screw 
clockwise.

1

Turn 
the screw 
anti clockwise.

2-20

(1) Connect the oscilloscope to TP5 (PB FM:8F) on the P/R board

and Audio Out terminal, and connect the external sync to
TP4 (D  FF:7F) on the P/R board.

(2) Play back the alignment tape VFK1742 to observe the FM

waveform and audio signal.

(3) During playback, press the tracking buttons (+, –) simultane-

ously to enter the tracking center position.

(4) Loosen the screws 

4

 and 

5

 and set the A/C head position

bit as shown in Fig. 2-5-5.

(5) Rotate the A/C head position bit to adjust the A/C head posi-

tion so that the FM waveform becomes maximum and the
“no-recorded” portion between the FM waveform and the
audio signal is within 3 fields.

(6) Play back the alignment tape VFK1741 and observe FM wave-

form.

(7) During playback, press the tracking buttons (+,–) simultane-

ously to enter the tracking center position.

(8) By adjusting the tracking, check that the FM waveform be-

comes maximum at the tracking center position.
(The FM level at the tracking center position should be -1 dB
or more against the maximum FM level.)

(9) If the maximum waveform is not obtained, rotate the A/C

head position bit to adjust the audio control head position so
that the maximum FM waveform is observed first time.

(10) Repeat the above step (6) – (9) to meet specifications of step

(8).

(11) Tighten the screws 

4

 and 

5

.

(12) Confirm the azimuth of the A/C head. (Refer to Section 2.5.2.)

The FM waveform becomes maximum and the 
“no-recorded” portion between the FM wave-
form and the audio signal is within 3 fields.

“No-recorded” portion

P/R
TP5 (FM): 8F

AUDIO
OUT

• Manner of external synchronization:

1

Set the oscilloscope's time sweep to 10 msec.

2

3 fields

In the condition that the oscilloscope is 
synchronized with D.FF signal, turn the 
oscilloscope's HOLD OFF control in the 
direction of (+) to stabilize non-recorded portion.

Drum side

A/C head 

assembly

A/C head position bit

Capstan side

5

4