Tape Transport Maintenance

Tape transport maintenance includes procedures for adjusting the supply and takeup reel brakes, the capstan pinch roller pressure and the tape speed adjustment.

6-1 TRANSPORT ACCESS↑ TOP

1. Disconnect tne plug of the power cable.
2. Place the equipment on its left side.
3. Remove six cross-recessed screws putting the under frame.
4. Remove one flat head socket cap screw of the takeup side putting ventilation channel.
5. Remove six hex socket head screws putting tne right side board in position.
6. Open the Control P.C.Board by removing four cross-recessed screws marked "OPEN".

⤢ zoomAn isometric view of the recorder's underside with the bottom cover removed, dashed leader lines pointing to the six cross-recessed screws, the flat head socket cap screw, and the six hex socket head screws named in the removal steps.

Figure 6-1 Tape Transport Access

6-2 BRAKE ADJUSTMENT↑ TOP

The brake system on each reel stops the rotation of the reel when power is removed.

The brakes are checked and adjusted with the power removed.

Since the brake force is different for each direction of rotation (brake differential), and there is but a single adjustment, the force is checked and adjusted for the best compromise force in each direction.

In the following steps, an empty 10 1/2 inch diameter NAB reel (4 1/2 inch diameter hub) is used and a length of cord or twine is wrapped on the hub.

A spring scale is attached to a small loop formed at the free end of the cord or twine.

If a 10 1/2 inch diameter NAB reel (4 1/2 inch diameter hub) is not available, a 7 inch diameter reel (2 1/4 inch diameter hub) may be used but all readings must be multiplied by a factor of 2.

Refer to Table 6-1 for the braking force specifications.

Proceed as follows:

1. Place an empty 10 1/2 inch diameter NAB reel on the supply reel table. Secure with a hold down knob.
2. Wind a length of cord or twine a few turns counterclockwise on to the hub. Tie a loop at the free end of the cord or twine.
3. Insert the hook of a 500 g (0-16 ounce) spring scale through the loop and hold the spring scale upright as shown in Figure 6-2.
4. Pull on the scale slowly to make the reel rotate counterclockwise (direction "B" in Figure 6-2). While being sure the cord does not rub against either flange, note the scale reading. The reading should meet the value listed on Table 6-1.
5. Wind the cord or twine in a clockwise direction on to the supply reel.
6. Repeat steps 3 and 4 to make the reel rotate clockwise (direction "A" in Figure 6-2).
   The reading should meet the value listed in Table 6-1.
7. If the readings were low in both directions, remove the brake spring (shown in Figure 6-3) from the existing anchor hole on the brake lever and install the spring in the next hole located farther away from tne brake solenoid.
8. If the readings were high in both directions, move the spring anchor point closer to the brake solenoid.
9. If the brake spring was moved, repeat steps 2 through 6 to check the results.
10. Repeat the brake adjustment procedure on the takeup reel.
    Note that a high braking force is present when the takeup reel is rotated clockwise.
    The braking force specifications are tne same as for the supply reel.

Table 6-1 Braking Force Specifications

A	145 to 175 grams (5.1 to 6.2 ounces)
B	315 to 385 grams (11.1 to 13.6 ounces)

⤢ zoomTwo tape reels seen from the front, each with a curved arrow labelled A and B for its two directions of rotation, and a spring scale hanging above the left reel's hub on a cord.

Figure 6-2 Brake Measurement

⤢ zoomA labelled diagram of the brake assembly, showing the brake solenoid, plunger, solenoid pin, stroke dimension, cushion, retaining rings A and B, brake arm, brake spring, brake drum, brake band, brake band guide and brake guide with their mounting screws.

Figure 6-3 Brake Assembly Location

6-3 CAPSTAN PINCH ROLLER PRESSURE ADJUSTMENT↑ TOP

The capstan pinch roller's pressure against the capstan is determined by the pinch roller solenoid spring.

This force is adjusted by means of the nut shown in Figure 6-5.

The nut is adjusted to obtain a force of 2.7 ~ 2.9 kg (5.9 ~ 6.4 pounds).

The resistance of the solenoid coil rises with the temperature and causes the solenoid's force to decrease.

Therefore, do not adjust the pinch roller's pressure until the recorder has been operated in the play mode for at least 30 minutes.

The following procedure should be adhered to.

1. Remove the pinch roller cap by removing the screw on it.
2. Screw the hex socket head screw of M3 (length = 25 ~ 30 mm) into this internal thread (screw hole).
3. Press the EDIT pushbutton, and then press the PLAY pushbutton. The pinch roller will move to make contact with the capstan and both will rotate.
4. Measure pinch roller pressure by using the Pusn function (piston part, not hook part) of the spring scale. Put the end of piston part of a 3 kg (0 ~ 10 pounds) spring scale on M3 hex socket head screws from the direction of the capstan shaft. (shown in Figure 6-4.) At this time do not touch the capstan shaft with piston part.
5. Push on the scale and note the scale reading when the pinch roller just loses contact with the capstan (the pinch roller stops rotating). The scale reading should be 2.7 ~ 2.9 kg (5.9 ~ 6.4 pounds).
6. If a proper scale reading was not obtained in step 5, loosen the locknut and adjust the pressure nut as shown in Figure 6-5. (Turning the pressure nut towards the spring increases pinch roller pressure.) Tighten the locknut.
7. After adjustment has been completed, check that the plunger of the solenoid reaches bottom within the solenoid coil (the pinch roller can easily be pushed away from the capstan). If the plunger of the solenoid does not reach bottom, loosen the locknot and turn the pressure nut away from the spring until the plunger of the solenoid reaches bottom. Recheck the pressure adjustment and tighten the locknut.

⤢ zoomThe pinch roller and its shaft with a spring scale's piston pressed against a hex socket head screw from the capstan side, arrows marked PUSH showing the measuring direction on both sides.

Figure 6-4 Pinch Roller Pressure Measurement

⤢ zoomThe pinch roller solenoid's pressure-adjustment linkage, with a pressure nut and locknut on a threaded rod and curved arrows marked Loosen (counterclockwise) and Tighten (clockwise).

Figure 6-5 Pinch Roller Pressure Adjustment

6-4 TAPE SPEED ADJUSTMENT↑ TOP

The tape speed can only be adjusted on the dc servo capstan motor, by using the speed adjustment controls on the Servo Control P.C. Board.

This adjustment follows the tape speed measurement in Section 7, and the speed adjustment controls shown in Figure 6-6 are adjusted as necessary.

It is important that the PITCH CONTROL should be placed in the "IN" fixed position during tape speed adjustment.

⤢ zoomThe capstan servo control P.C. board outline with its edge connector at the right and two speed trimmers near its lower edge, labelled H and M.

M : 7 1/2 ips
H : 15ips

Figure 6-6 Capstan Servo Control P.C.B.

6-5 TAPE TRANSPORT TIMING CHART↑ TOP

⤢ zoomThe control timing chart's inputs and outputs blocks stacked together: a MODE row of transport commands above the STOP, F.FWD, RWD, PLAY, REC, MEMORY, SAFETY, EDIT, PHOTO 1&2, CUE, ZERO, SIGN, REC READY/SAFE and T.T RESET input waveforms, and the actual tape motion, reel motor, brake solenoid, REC LED, EDIT LED, pinch solenoid, capstan on/off, REC to amp, F.WIND, MOVE/STOP, CUE to amp and direction output waveforms below.

* REEL MOTOR SUPPLY VOLTAGE (AC)

REEL SIZE	LARGE	SMALL
A	100 V	80 V
B	28 V	26 V
C	52 V	48 V
D	44 V	40 V

** SOLENOID SUPPLY VOLTAGE (DC)

	VOLTAGE
E	27 V
F	12 V
G	22 V
H	17 V

Figure 6-7 Control Timing Chart

6-6 RECORDING PROCESS TIMING CHART↑ TOP

⤢ zoomThe recording process timing chart, plotting the REC. COMMAND, MONITOR INPUT, MONITOR SEL/REP, REC. RELAY, REC. AUDIO SIGNAL, REC. BIAS and BIAS waveforms around the recording interval, with delay intervals t1 through t8 marked at the transitions into and out of recording.

t1:	MONITOR SEL/REP OFF & REC. RELAY ON operate time	; 36 msec
t2:	REC. AUDIO SIGNAL start delay time	; 54 msec
t3:	REC. BIAS start delay time	; 72 msec
t4:	REC. BIAS rise time	;117 msec
t5:	REC. BIAS fall time	; 40 msec
t6:	REC. RELAY & REC. AUDIO SIGNAL release delay time	; 54 msec
t7:	MONITOR SEL/REP ON operate time	; 72 msec
t8:	MONITOR INPUT OFF operate time	;126 msec

Figure 6-8 Recording Process Timing Chart