MICRO SEIKI MA-707 Dynamic Balance Gimbal Bearing Tonearm User Manual

MICRO SEIKI MA-707 Dynamic Balance Gimbal Bearing Tonearm

Parts overvieww

List of parts supplied

• Counterweight (main)
• Sub-weight main
• Additional weight
• Headshell
• Overhang gauge
• Screwdriver
• Installation screws
• Six  sided wrench
• Output lead

Mounting tonearm

Place the template on the motor board as shown in photo 3, and settle the position where the tonearm is to be mounted.

Caution
When selecting the tonearm installation take care that the position chosen does not Interfere with the drive motor. but instead will allow smooth operation.

After settling the tonearm position, drill a 28mm dia-meter hole for the tonearm base.  lnsen the tonearm base into the mounting hole, and secure it temporarily by the nut. If using the motor board that is more than 30mm thick. make the hole cut larger only 1rom backside until the armbase shaft comes out. Pass the output cable through the armbase hole, and plug the output cable into the tonearm shaft con nector.

Set the tonearm at an angle of 60° as shown in fig. 2, and secure it.

Tonearm assembly

Cartridge installation and adjustment

Installation

Install the cartridge into the headshell provided using screws of a suitable length.

Carlridge connection

Connect the headshell leads to the cartridge using tweezers as shown above. Take care to make these connections correctly as error will lead to hum or output signal failure. The colors of the leads are as follows

Overlian adjustment

The MA-707 is designed to operate with minimal tracking error when the overhang is 15 mm. In order to adjust the cartridge correctly, place the enclosed overhang gauge over the headshell as shown in photo 5. loosen the cartridge securing screws and align the stylus to the line middle on the gauge by moving the cartridge either forward or backward.  When a diffrent cartridge is installed in the headshell, be sure to readjust, using the method described above.

Tonearm assembly

Secure the tonearm in the arm rest. Then mount the counterweight onto the end of the tonearm shalt, turning it in the direction.

Install the shell with cartridge into the tonearm and secure it by the nut.

Tonearm adjustment

Effective mass adjustments

In order to utilize characteristics of the cartridge enough, first of all, it is necessary to ascertain whether the total mass of the cartridge-tonearm assembly the mass of the movable components of the tonearm such as its pipe) is compatible with the compliance of the cartridge being used. For example, if a high com-pliance cartridge is used in conjunction with a heavy tonearm, the resonance frequency (fo) will become extremely low, and brings bad tracing ability and also rumble. Generally the optimum resonance frequency is considered to be around 10Hz. The MA 707 is designed so that the resonance fre• quency will be around 10Hz when used with medium to high compliance cartridges (practically all moving magnet type cartridges fall into this range). However, when using a cartridge with a relatively low compli• ance. it is possible to adjust the effective mass ot the tonearm by using the additional weights provided and thereby make it possible to give full play to the charac-teristics of the cartridge being used.Instances where use of weights provided is indicated.

The compliance of a cartridge is indicated in the specifications of a cartridge. For example, a cartridge might have a compliance rating of 25 x 10·6cm /dyne. The higher the first figure of this formula, which in this instance ,s 25, the ·higraer t.he ompliance. However. it is also true that the metl’u:;fd of compliance rating indi-cation is not standardized r.nong manufacturers, there being the general indication static indication  a dynamic compliance indication, so for further details, it is recommended that enquiries be directed to the manufacturer of the cartridge that is to be use.

Using weights provided

The securing knob of the weight provided is loosened and it is fitted onto the pipe of the tonearm as shown in the illustration. After it has been set to the recommend-ed value, ascertain that the weight is fitted horizontally, after which it may be secured in position by means of the securing knob. When using the weights provided. be sure to also use the sub-weight into the tonearm end.

Sub weight

When using the weights, the sub-weight must also be used. The sub-weight is fitted into the tonearm end as shown in Figure 8, turning it in the direction of the arrow as far as it will go.

Adjusting horizontal balance

Align OFF on the stylus pressure knob to the stylus pressure reference mark.

Align OFF on the anti-skating control knob to the bias reference Ii ne. (photo 9)

Lower the arm lift lever as pictured in photo 10, then release the tonearm from the arm rest.

S1 porting the headshell iand counterweight as illustrated in photo the counter.weight, moving backward.,. ar forward, until the proper balance is achieved. Tonearm balance is achieved when (t) the car-tridge weight and counterweight cancel each other out: and (2) on release, the tonearm adopts the position shown rn fig. 9.
The example in fig. 10 illustrates too much weight at the counterweight end of the tonearm shaft. Turning the counterweight in the direction Indicated will achieve correct balancing. On the other hand, the example shows too little weight at the counterweight end of the tonearm shaft. Turning in clockwise direction as indicated will rectify this imbalance.

Application of tracking force

Turn the tracking force adjustment knob and set a value which is suitable for the installed cartridge to the tracking force level line. If for example, the cartridge to be used operates at a tracking force of 1.5 grams, turn the adjustment knob until the 1.5 mark on the scale is opposite the level line.

Anti skating adjustment

This mechanism cancells the force that tends to pull the stylus toward the center of the record during play-ing. It functions to always provide even pressure between left and right record groove walls. Since the anti-skating device of the MA-707 responds to the tracking force set the bias knob (photo 13) to the same value as the tracking force of the employed cartridge.

Adjusting tonearm height

The height of the tonearm must be adjusted so that it is parallel to the surface of the record. This height will determine depending upon the cartridge being used. Place a record on the turntable, move the tonearm to a place over the record groove, and lower the tonearm lifter. Loosen the height adjusting screw of the tonearm and adjust the height of the tonearm so that the tone-arm is parallel to the surf ace• of the record when viewed from the turntable.

Adjust so that the tonearm is Parallel with the surface of the record

Adjustment of the arm lifter operation range

Raise the arm lift lever and move the-tonearm to .a point above the record surface. Determine whether the distance between the stylus and the record surface is adequate. If necessary, regulate the adjust-ing screw.

Dimensions required

MA-707 Specifications

• Tv.pe : Dyi:iamic balance tonearm
• Overall length: 315mm (12-3/8 inch)
• Effective length :237mm (9-3/8 inch)
• Overhang:  15mm (5/8 inch)
• Offset angle:21 ° 50
• Tracking error angle :Less than 1.5 °
• Height range: 43 ~83mm ( 1-3/4 ~3-1 /4 inch)

Recommended cartridge

• Weights :4~ 12g (0.14~4.2oz)
• Lateral motion sensitivity . 10mg Vertical motion sensitivity 15mg
• Anti skating device: Spring tension type Establishing of anti skating force: Relative to stylus pressure
• Tonearm lifter: Delayed action type
• Output cable:5 connector plug-in low capacity design (55PF /m) shielded cable
• Headshell weight:49 (0. 14oz)
• Connector: Semi-integrated type, with hard gold platin.

Read User Manual Online (PDF format)

Download This Manual (PDF format)

Download this manual  >>