Major Component Replacement Procedures

4-1 TAPE TRANSPORT↑ TOP

In order to gain access to the tape transport components, place the recorder in an upright position and remove rear cover, two side panels, and top panel (16 screws total).

Refer to Section 6 for parts lists and exploded views of the transport assembly to aid in the identification of the various components.

4-1-(1) REEL TABLE REPLACEMENT AND HEIGHT ADJUSTMENT↑ TOP

The reel table may be removed by removing three cross head screws accessible from the front of the transport. To adjust the reel table height, loosen two hexagonal socket head screws shown in Fig. 4-1, adjust height and retighten screws.

⤢ zoomFig. 4-1 Reel Table and Motor: an exploded isometric view of the reel table and turntable shaft, with leader lines to three reel table fixing screws, two reel table height screws, four motor mounting nuts and four motor mounting cross head screws, the capstan motor assembly shown below

Fig. 4-1 Reel Table and Motor[sic]

4-1-(2) SUPPLY OR TAKEUP REEL MOTOR REPLACEMENT↑ TOP

To replace the supply or takeup motor proceed as follows:

1. Loosen two hexagonal socket head screws on the reel shaft holder (Fig. 4-1) and remove reel table and holder.
2. Tag and unsolder motor leads from the attached printed circuit board.
3. Remove four motor mounting M4 nuts.
4. Remove four motor mounting crosshead screws.
5. Install new motor in the reverse order of removal and adjust reel table height.

4-1-(3) POWER TRANSFORMER REPLACEMENT↑ TOP

To replace the power transformer (refer to EXPLODED VIEW 2), proceed as follows:

1. Tag and unsolder all transformer leads from the terminal.
2. Remove four M4 nuts that secures[sic] the transformer to the transport. (Ref. No. 2-18)
3. Install new transformer in the reverse order of removal and resolder leads to the terminal of the transformer.

4-1-(4) CAPSTAN MOTOR REPLACEMENT↑ TOP

The capstan motor should be replaced with servo control printed circuit board assembly, to replace the capstan motor proceed as follows: (Refer to EXPLODED VIEW 4)

1. Remove connector on servo control printed circuit board assembly located above capstan.
2. Remove servo control printed circuit board assembly with mounting plate by turning four M3 crosshead screws "B" on mounting plate.
3. Remove capstan dust cap from face of transport. (Ref. No. 4-3)
4. Remove capstan mounting plate with capstan motor by removing four M4 crosshead screws "A" on the mounting plate.
5. Remove the capstan motor by removing three M4 crosshead screws "C" on the mounting plate and install new capstan assembly in the reverse order.

⤢ zoomFig. 4-2 Capstan Motor Location: an isometric view of the capstan motor assembly mounted beneath the transport deck, with leader lines to the servo control P.C.B. assembly, its connector and the power supply P.C.B. assembly above, and the mounting plate, four M3 cross head screws "B", four M4 cross head screws "A" and three M4 cross head screws "C" below

Fig. 4-2 Capstan Motor Location[sic][sic]

4-1-(5) BRAKE BAND OR BRAKE SOLENOID REPLACEMENT↑ TOP

When a new brake band or new brake solenoid is installed (Fig. 2-2), it is necessary to position the brake guide and/or brake solenoid to ensure that there is uniform brake band clearance around the brake drum when the solenoid is energized. Also the brake solenoid plunger must bottom in the solenoid housing when the solenoid is energized. When the solenoid is deenergized, the brake band should uniformally[sic] contact the drum surface. After installation, perform the Brake Adjustment procedure and the Tape Tension Adjustment procedure given in Section 2 of this manual. After completion of the adjustments place the recorder in play mode for 30 minutes. Then press STOP and PLAY pushbuttons to ensure that the solenoid bottoms when it is hot.

⤢ zoomFig. 4-3 Brake Assembly Location: a front view of the brake assembly mounted behind the brake drum, with leader lines to E ring A, the brake spring, the brake lever, E ring B, the brake solenoid, the solenoid pin and its stroke dimension, two cross head screws for the brake spring, two hexagonal screws for the solenoid housing, and, below the drum, the brake band, the brake guide and cord cramper

Fig. 4-3 Brake Assembly Location[sic][sic][sic][sic]

To replace brake band, proceed as follows.

1. Remove spring pin on brake lever.
2. Remove two cross head screws, and replace brake band.

To replace brake solenoid, proceed as follows.

1. Remove brake spring and remove E ring A.
2. Remove E ring B on solenoid pin and remove solenoid pin.
3. Remove solenoid housing with plunger by removing two hexagonal socket screws.
4. Install new solenoid housing with plunger and set solenoid housing for 0.2±0.002 inch/in position[sic] in solenoid plunger stroke from the bottom.

4-1-(6) PINCH ROLLER REPLACEMENT↑ TOP

To replace the pinch roller assembly proceed as follows:

⤢ zoomFig. 4-4 Pinch Roller Removal: two side-by-side exploded isometric views of the pinch roller stack lifted off its shaft on the transport face, one for Models 2SD₂, QXD showing the pinch roller cap, washer and pinch roller, and one for Models ½QXD, 8SD showing the pinch roller cap, retaining ring, two ball bearings, collar and pinch roller

Fig. 4-4 Pinch Roller Removal[sic][sic][sic]

1. Remove pinch roller cap. On Models 2SD₂ or QXD, turn pinch roller cap counterclockwise. On Models ½QXD or 8SD, remove screw on pinch roller cap.
2. Install new pinch roller. On Models ½QXD or 8SD, replace 2 ball-bearings at the same time.
3. Reinstall nylon washer and pinch roller cap in the reverse order.

4-2 HEAD ASSEMBLY REPLACEMENT↑ TOP

This section provide[sic] a description of the head assembly, procedures for changing head stacks and adjustment procedures for adjusting head azimuth (tilt), head height, head zenith (perpendicularity) and tape wrap (racking). These adjustments are required whenever a head stack is replaced. Note that a different replacement and adjustment procedure is provided for Otari Models MX-5050-2SD₂, QXD and for Otari Models MX-5050-½QXD, 8SD.

4-2-(1) For MX-5050-2SD₂ or QXD↑ TOP

DESCRIPTION

The head assembly is mounted on three tape-guide posts and secured in place by three screws labled[sic] "M" in Fig. 4-5.

⤢ zoomFig. 4-5 Top View of Head Assembly: the head assembly's screw layout seen from above, with S, Z, A, W, M, and H letters marking the insulating-shield, zenith, azimuth, wrap, mounting, and height screws across the three head-stack positions

Fig. 4-5 Top View of Head Assembly

The insulating shield for the head assembly printed circuit board is secured by screws labled[sic] "S". Each head stack is secured to a bracket by screws labled[sic] "W" with a spacer between the bracket and head stack. Each bracket is suspended from the head base by three spring-loaded screws labled[sic] "H", "A", and "Z". Screws labeled "W" are used to adjust tape wrap. Screws labeled "H", "A", and "Z" are used to adjust height, azimuth, and zenith.

A head stack may be removed and re-lapped (face resurfaced) if the amount of wear is small and only an indication of poor head-to-tape contact is evident. Poor contact is a result of improper adjustment and is evidenced by loss of high frequency response of the record or reproduce head stack, difficulty in achieving bias peak (record stack), or insufficient erase stack erasure.

HEAD STACK REPLACEMENT

To change a head stack, proceed as follows:

1. Lift head cover, remove AC power cord.
2. Remove three screws labeled "M" and pull out the head assembly from head connector.
3. Tag and unsolder (use low wattage pencil type iron to prevent damage) leads at rear terminal of the head stack.
4. Remove head stack by removing two screws labeled "W".
5. Install new head stack and resolder leads.
6. As a preliminary adjustment, measure the distance between the head base and the bracket at a point near spring-loaded screws "A", "Z", and "H". If necessary adjust screws for equal spacing.
7. Lay a piece of ¼-inch tape over the spacers and head stacks as shown in Fig. 4-6. Note if the leading and trailing wrap angle around the head stack is equal. If not equal, correct by loosening screw "W", adjusting head stack, and retightening screws. Remove the three screws and spacers installed in step 7.
8. Remount the head assembly. Perform the appropriate head alignment procedure given below.

⤢ zoomFig. 4-6 Front View of Head Assembly: a front elevation of the head base, bracket, and spacer beneath the tape wrap path, dimensioned ¼ inch for full-track or 2-track heads and 7/32 inch for 4-track, above the erase, 4-track reproduce, record, and 2-track reproduce head stacks

Fig. 4-6 Front View of Head Assembly[sic]

Head alignment and following adjustment are necessary whenever head is replaced.

1. In case of reproduce head replacement. A. Reproduce Equalization Adjustment (See 3-5-(3) ) B. SRL Calibration (See 3-5-(4) )
2. In case of record head replacement. A. Bias Buffer Amplifier Adjustment (See 3-6-(1) ) B. Bias Calibration (See 3-6-(2) ) C. Record Level Adjustment (See 3-6-(4) ) D. Record Level Calibration (See 3-6-(5) ) E. Record Equalization Adjustment (Refer to Instruction Manual) F. SEL/REP Level Adjustment (See 3-6-(7) )
3. In case of erase head replacement A. Bias Buffer Amplifier Adjustment (See 3-6-(1) ) B. Bias Calibration (See 3-6-(2) )

RECORD OR REPRODUCE HEAD ADJUSTEMNT[sic]↑ TOP

Follow the procedure for Reproduce Amplifier Alignment given in Section 3 of this manual. For the final adjustment of a record stack, the height and azimuth adjustment may be accomplished in the same manner as for a reproduce head stack by playing back an alignment tape with the recorder in the selective reproduction mode (SEL/REP switches "in"). Use the 10 kHz tone for azimuth adjustment.

ERASE HEAD ALIGNMENT↑ TOP

Erase head azimuth is not critical, however wrap angle and head height relative to the record head is important to achieve maximum efficiency. Poor erasure is often caused by misalignment of the erase head. Before making any attempt to adjust the erase head stack, an entire electronic alignment procedure (reproduce, record, and bias amplifier alignment) should be performed so that the record and reproduce head heights are correct, SRL/CAL setting is correct, and bias and record levels are properly calibrated. If[sic] should be also noted that in some cases, high coercivity tape can be the cause of poor erasure.

An approximate erase head adjustment can be accomplished using headset or a speaker/amplifier. However, for precise alignment, a wave analyzer should be used. Proceed as follows:

1. Follow the procedure for Erasure Test steps 1 through 6 given in Section 3 of this manual.
2. Observe reading on wave analyzer and turn screw "H" (Fig.4-5)[sic] ¼ turn clockwise. If the reading decreased, turn screw "A" and "Z" ¼ turn clockwise. If the reading increased when "H" was turned ¼ turn clockwise, turn "H" counterclockwise past the original setting to ¼ turn counterclockwise. If the reading decreased, turn screw "A" and "Z" counterclockwise by the same amount.
3. Repeat step 2 in small increments to achieve a minimum reading on the wave analyzer. Typical amount of erasure should be 65 dB or better. Note: After "H" is turned, be sure to turn "A" and "Z" the same amount.
4. If the adjustment of erase head height alone cannot achieve satisfactory erasure, set screw "H", "A", and "Z" for minimum reading on the wave analyzer. Note that there are two vertical gaps on the face of the erase head. The trailing gap has the most effect on erasure and must be in good contact with the tape. Loosen screws "W" slightly and rotate the erase head stack for a minimum reading on the wave analyzer. Tighten screws "W".

⤢ zoomFig. 4-7 Bottom View of Head Assembly: the head assembly seen from below, with the ¼-inch-diameter by ¾-inch spacers dimensioned above the four head-stack brackets and the tape path labeled where it wraps across them

Fig. 4-7 Bottom View of Head Assembly

⤢ zoomFig. 4-8 Head Alignment: three diagrams showing the head's parallel position for zenith, the equal wrap angle of the tape across the head stack, and the right-angle check for azimuth

Fig. 4-8 Head Alignment

4-2-(2) For MX-5050 ½QXD or 8SD[sic]↑ TOP

DESCRIPTION

The head assembly is mounted on three screws labeled "M" in Fig. 4-9.

⤢ zoomFig. 4-9 Top View of Head Assembly: the ½QXD and 8SD head assembly's screw layout seen from above, with F and M letters marking the head-base and mounting screws across the three head supporters

Fig. 4-9 Top View of Head Assembly

Each head base is directly secured to assembly base by screws labeled "F".

HEAD STACK REPLACEMENT↑ TOP

It is important that power supply must be removed before replacing the head.

For Model ½QXD, proceed as follows:

1. Remove three screws labeled "F" and unsolder the head leads on the head P.C.B. assembly.
2. Install new head in reverse order.

For Model 8SD, proceed as follows:

1. Reproduce head or both record and erase heads are replaced with head connector. Pull out head connector (MR16M) and remove head assembly by removing three screws labeled "F". Install new head assembly in reverse order.
2. Either of record head and erase head is replaced, unsolder the head leads from head connector and remove head assembly by removing three screws labeled "F". Install new head assembly in reverse order and resolder the head leads.

Head alignment and following adjustment are necessary whenever head is replaced.

1. In case of reproduce head replacement. A. Reproduce Equalization Adjustment (See 3-5-(3) ) B. SRL Calibration (See 3-5-(4) )
2. In case of record head replacement. A. Bias Buffer Amplifier Adjustment (See 3-6-(1) ) B. Bias Calibration (See 3-6-(2) ) C. Record Level Adjustment (See 3-6-(4) ) D. Record Level Calibration (See 3-6-(5) ) E. Record Equalization Adjustment (Refer to Instruction Manual) F. SEL/REP Level Adjustment (See 3-6-(5) )[sic]
3. In case of erase head replacement A. Bias Buffer Amplifier Adjustment (See 3-6-(1) ) B. Bias Calibration (See 3-6-(2) )

HEAD ALIGNMENT

1. Fix head lightly and adjust head so as the tape will touch the head left and right symmetrically as shown in the Fig. 4-1.1 (C)[sic] (Paint the head face with a soft crayon, run the tape in about ten sec, and see the crayon marks rubbed away by the tape.)
2. If head height is incorrect, add a thin seet[sic] (shim) between the head and the head base as shown in fig. 4-11(b)[sic] and adjust head height for identical top and bottom head pole with the width of the threaded tape as shown in fig.[sic] 4-10.
3. Azimuth adjustment for erase head is not necessary. Azimuth adjustment for reproduce head is adjusted by adding a thin seet[sic] (shim) for maximum output reading in test tape reproducing mode. Azimuth adjustment for record head is adjusted by adding a thin seet[sic] (shim) in record-reproduce mode after reproduce head adjustment is complete.

⤢ zoomFig. 4-10 Front View of Head Assembly: a front elevation of the ½QXD and 8SD head stacks and their mounting coils, used to check the top and bottom head pole width against the threaded tape

Fig. 4-10 Front View of Head Assembly

⤢ zoomFig. 4-11 Head Alignment: three diagrams for the ½QXD and 8SD heads showing (a) the parallel touch position, (b) where the alignment shim sheets are added, and (c) the equal wrap angle of the tape across the head

Fig. 4-11 Head Alignment[sic]

If head height is incorrect in azimuth adjustment, readjust height and azimuth adjustment.

Since these adjustment[sic] may be affected by the clamping effect of screw labeled "F", tightly fix the head assembly before making these adjustment[sic].

Refor[sic] to Section 3 to aid for azimuth adjustment procedure.

4-2-(3) ACCESS TO ELECTRONIC ASSEMBLY↑ TOP

The record/reproduce electronics is composed on plug-in type printed circuit boards. Access to electronics assembly may be obtained by following procedure.

Refer to EXPLODED VIEW 12, 13, 14, and 15 in Section 6 to aid access to electronic assembly.

1. Remove the connectors on the rear of electronics.
2. Pull the (Ref. No. 12-2, 12-4) off, and remove the face panel by removing the (12-6) at the both side on the face panel.
3. Remove (14-1) at the both side on the top panel and draw the electronics out.

4-3 INSTALLATION OF OPTIONAL TRANSFORMER↑ TOP

4-3-(1) INSTALLATION OF INPUT TRANSFORMER↑ TOP

Fig. 4-12 shows circuity[sic] of unbalanced input and balanced input. To install input transformer, proceed as follows:

⤢ zoomFig. 4-12 Input Circuitry: schematics of the standard unbalanced input, with its 47k and 82K resistors and 10K load feeding the connector, and the optional balanced input, with its four 220-ohm resistors and 600-ohm load around the ET-21-181 transformer and the 82K and 10K resistors past it

Fig. 4-12 Input Circuitry[sic]

1. Remove rear panel by removing part No. 15-49 at the both side on rear panel.
2. Install transformer bracket to left side inside the panel as shown in Fig. 4-13 and insert the input transformer.
3. Unsolder wires from XRL[sic] connector and wire as shown in Fig. 4-14.
4. Change leads from terminal 3 and 8 of connector to terminal 1 and 10.
5. Install rear panel in reverse order.
6. After all of above modification, test record.

⤢ zoomFig. 4-13 Input Transformer Installation: an exploded isometric view of the ET-21-181 input transformer and its bracket mounting to the rear panel rail

Fig. 4-13 Input Transformer Installation

⤢ zoomFig. 4-14 Input Transformer Wiring: the CN11-F connector's odd-numbered pins wired through the ET21-181 transformer to the LINE INPUT R connector's pins 1, 2, and 3, with the black shield, white cold, and orange hot leads labeled[sic]

Fig. 4-14 Input Transformer Wiring[sic][sic]

4-3-(2) INSTALLATION OF OUTPUT TRANSFORMER↑ TOP

Fig. 4-15 shows circuity[sic] of unbalanced output and balanced output. To install input transformer[sic], proceed as follows:

⤢ zoomFig. 4-15 Output Circuity: schematics of the standard unbalanced output, with its 3K switch resistor and 600-ohm load feeding the output connector, and the optional balanced output, with its 3K switch resistor and shield lead through the ET-31-182 transformer and 600-ohm load to the output connector

Fig. 4-15 Output Circuity[sic]

1. Remove rear panel by removing four screws at the both side on rear panel.
2. Install output transformer to about center inside the panel as shown in Fig. 4-16.
3. Unsolder wires from XRL[sic] connector and wire as shown in Fig. 4-17.
4. Install rear panel in reverse order.
5. After above wiring, adjust reproduce level (refer to 3-5-(4) SRL ADJUSTMENT in Section 3).

⤢ zoomFig. 4-16 Output Transformer Installation: an exploded isometric view of the output transformer bracket and two transformer housings mounting to the rear panel rail

Fig. 4-16 Output Transformer Installation

⤢ zoomFig. 4-17 Output Transformer Wiring: the terminal block's pins 1 through 8 wired through the 600-ohm ¼-watt resistor to the LINE OUTPUT connector's pins 1, 2, and 3, with the white, orange, and shield leads keyed in the legend below

Fig. 4-17 Output Transformer Wiring[sic]