DUAL 604 (01) PDF Document

To remove the motor electronics on your DUAL 604, follow these steps:

1. Extract the unit plug from the power line. Lift off the platter. Bring the unit into the head position.

2. Remove the machine screws and the cover of the power part.

3. Unsolder the connecting leads to the motor and generator. Open the twists of the holding angle with pliers. Remove the motor electronics, screws, and holding angle.

4. Carefully pull off the motor electronics system from the motor.

5. Fix the replacement motor electronics. Solder the connecting cables according to the connection diagram.

6. Slide the cover over the power part and fix it with the machine screws.

7. With the unit in its normal position, connect it to the power line. Switch on the unit and check power consumption during operation:

220 V/50 Hz approx. 15 mA

110 V/60 Hz approx. 25 mA

Check nominal speeds. If necessary, readjust as described in the manual.

Follow this procedure to replace the motor mechanics on the DUAL 604:

1. Extract the unit plug from the power line and remove the platter.

2. With the unit in the head position, remove the machine screws and washers. Carefully pull off the motor electronics board together with the cover from the motor.

3. Loosen the connection for operating voltage at the het plate. Unsolder connecting leads to the speed fine adjustment, rotary switch, and the generator. Open twists of the holding angle with pliers.

4. Loosen the threaded pins and remove the platter cone. Remove the three screws. Lift off the motor mechanics.

5. Put the platter cone on the new motor mechanics and fix it. Fix the new motor mechanics with the three screws. Fix the holding angle with screws. Insert the motor electronics and twist the holding pieces. Solder on the connecting leads.

6. With the unit in its normal position, connect it to the power line. Switch on the unit and check power consumption when operating. Check nominal speeds and readjust if necessary.

On the DUAL 604, each of the two standard speeds (33 1/3 and 45 rpm) can be varied by about 10%. The variable speed control, located in the voltage divider, is adjusted by turning the pitch control knob. This alters the differential amplifier and the motor speed accordingly.

To set the nominal speeds on your DUAL 604, bring the pitch control knob into the center position. Use the controls (R8 and R9) on the motor electronic system to adjust the nominal speeds. Control R8 is used for 33 1/3 rpm, and R9 is for 45 rpm. Check the speed with the strobe disk.

The DUAL 604 can be changed to a nominal speed of 78 rpm instead of 45 rpm. To change the speed, bring the fine speed control (pitch knob) into the center position. Using control R9 on the motor electronics board, adjust for 78 rpm. Check the speed with the strobe disk.

The stroboscope on the DUAL 604 allows for accurate setting of the 33 1/3 and 45 rpm platter speeds. Strobe markings are provided on the outer edge of the platter for 50 and 60 Hz line frequencies.

When the platter is rotating at the exact speed, the lines of the stroboscope appear to stand still. If the lines move in the direction of the platter’s rotation, the speed is too high. If the lines move backwards, the platter is rotating more slowly than the nominal speed. Adjustments are made separately for each speed using the “pitch” controls.

It is possible for the stroboscope lines to appear to move slightly (“wander”) even when the speed is set correctly. This is because the electronic drive motor operates independently of the line frequency, while the stroboscope light relies on the AC line frequency for its timing. Small fluctuations in the AC line frequency can cause this effect, even though the platter speed remains constant and accurate.

To remove the tonearm from the bearing frame of the DUAL 604, follow this procedure:

1. Clamp the unit in a repair stand. Set the spring housing scale to zero. Lock the tonearm and remove the counterbalance weight.

2. Turn the unit over and remove the screening sheet. Unsolder the tonearm connections on the muting switch.

3. Remove the safety washer, washer, and bearing. Move the positioning bar towards the muting switch.

4. Unlock the tension spring, loosen the safety washer, and remove the skating lever.

5. Remove the safety washer and sliding washer, and take the shut-off bar from the segment.

6. Remove the hex nuts and segment.

7. Hold the tonearm. Remove the hex nut and the complete tonearm with its bearing.

Reverse this procedure when reassembling.

To remove the entire tonearm assembly:

1. Secure the unit in a repair jig. Remove the counterbalance weight and undo the fixing screw. Set the tracking force scale to zero.

2. Move the unit into the head position. Remove the screening plate. Unsolder the tonearm connections on the muting switch.

3. Move the unit into its normal position. Remove both mounting screws (SW 4.5).

For installation, proceed in the reverse order.

To replace the spring housing, first remove the tonearm from the bearing frame as described in the manual. Then, loosen the lock nut and threaded pin. Unscrew the bearing screw. Lift the bearing frame and remove the spring housing. When installing, ensure the helical spring catches the bearing frame. Slide in the washer and tighten the bearing screw. Reinstall the tonearm and set the bearing play as described for adjusting the tonearm bearing.

To adjust the tonearm bearing on the DUAL 604, first balance the tonearm exactly. Both the horizontal and vertical bearings must have slight, just perceptible play.

The horizontal tonearm bearing is correctly adjusted when, at an anti-skating setting of “0.5”, it slides without resistance when touched.

The vertical tonearm bearing is correctly adjusted when it swings in after being touched.

The play of the horizontal tonearm bearing should be adjusted with its threaded pin, and the vertical tonearm bearing with its respective threaded pin.

To check the anti-skating device on your DUAL 604, follow these steps:

1. Balance the tonearm correctly.

2. Set the knurled anti-skating ring to 0. The tonearm should remain at any desired point within its turning range.

3. The hole of the skating lever should be in alignment with the center line of the tonearm. Adjustment is made by the eccentric pulley (E), which is accessible through the hole in the installation plate between the knurled ring and the tonearm.

4. Then set the knurled ring to “0.5”. The tonearm should now smoothly rotate from the platter center to its rest.

Any further alteration should only be done by an authorized service station with a test record.

The lift height of the cue control on the DUAL 604 can be varied by turning the sleeve (202). The distance between the record and the needle should be 5-7 mm, with the tonearm having a height play of 1-2 mm. Make further adjustments by means of the set screw (57).

To replace the cue control plate on the DUAL 604, follow these steps:

1. Clamp the unit in a repair stand and lock the tonearm. Turn the unit over.

2. Remove the safety washer, washer, and bearing. Lift the positioning bar and move it towards the muting switch.

3. Unlock the tension spring. Loosen the safety washer and lift the skating lever. Remove the safety washer and sliding bar. Lift the shut-off bar from the segment.

4. Remove the hex nuts and segment.

5. Remove the machine screws. Hold the tonearm bearing. Unscrew the hex nut and remove the lift plate.

6. Secure the tonearm with the hex nut to prevent it from falling out.

Reverse this procedure when reassembling.

The set-down mechanism on the DUAL 604 uses a slide bar that positions recesses to catch a spring pin on the tonearm segment, defining the set-down point for 30 cm and 17 cm records. The mechanism can be disengaged by setting the control knob to the “-” position.

Adjustment Points:

a) Balance the tonearm exactly. Bring the control knob into the “-” position. Let the tonearm catch in the set-down point. Check the catch force with a spring balance; it should read 10-20 p. This force is adjustable by means of a threaded pin.

b) The tonearm set-down point can be adjusted by turning the set screw (42). Adjustment can be made for 17-cm and 30-cm records.

To prevent disturbing noises during automatic operation, the DUAL 604 is fitted with a short circuiter. In the neutral or zero position of the cam, there should be a clearance of approximately 0.5 mm between the contacts of the short circuiter. This clearance should be adjusted by bending the short circuit contact. The contacts should be sprayed with a suitable cleaning agent.

1. Segment

a) When fixing the segment, ensure there is a play of 0.5 mm between the segment and the switch lever.

b) The shut-off point may be varied with the eccentric (E) mounted on the segment.

2. Power Switch

When you swing in the tonearm, the slide of the power switch should have a play of 0.2 – 0.5 mm. Make adjustments by bending the switch lever.

If the tonearm head is not parallel to the platter, it’s likely that the seat of the tonearm head on the tonearm tube has changed during transit.

To fix this, remove the platter. Insert a screwdriver through the hole in the chassis mounting plate and loosen the screw at the tonearm head. Align the tonearm head correctly and retighten the screw.

If the stylus on your DUAL 604 slips out of the playing groove, it could be due to several causes. Here are the potential causes and their remedies:

Cause a) Tonearm is not balanced.

Remedy a) Balance the tonearm.

Cause b) Tonearm tracking force is too low.

Remedy b) Adjust the tracking force to the value stated by the cartridge manufacturer.

Cause c) Anti-skating setting is incorrect.

Remedy c) Correct the anti-skating setting.

Cause d) Stylus tip is worn or chipped.

Remedy d) Renew the stylus.

Cause e) Excessive bearing friction in the tonearm bearing.

Remedy e) Check the tonearm bearings and readjust if necessary.

Cause f) The steel ball of the shut-off bar is missing.

Remedy f) Renew the steel ball.

This issue is typically caused by excessive or insufficient damping as a result of contamination of the silicone oil in the lift tube.

To remedy this, you need to clean and re-lubricate the cueing mechanism. Remove the cue control plate, adjustment bush sleeve, lift pin, and compression spring. Clean the lift tube and lift pin. Smear the lift pin evenly with “Wacker Silicone Oil AK 300 000” and then reassemble the components.

If the tonearm moves on its own with tracking force and anti-skating set to zero, the cause could be one of the following:

a) The anti-skating device is maladjusted.

b) Tight tonearm leads are causing a torque on the tonearm.

To fix this:

a) Readjust the anti-skating device as described in the manual.

b) Slacken the tonearm leads to relieve any tension.

If the motor fails to switch off at the end of a record, the cause is likely a defective capacitor type suppressor in the power switch (short-circuit). The remedy is to replace the capacitor type suppressor in the power switch.

Acoustic feedback can be caused by the following issues:

a) Chassis components (e.g., connecting leads) rubbing on the board cut out.

b) Connecting leads fixed too strongly.

To resolve these issues:

a) Line up the mounting board cut-out according to the installation instructions and remove any obstructing leads.

b) Loosen or lengthen the connecting leads to ensure they are not under tension.

All bearings and friction points on the DUAL 604 are adequately lubricated by the manufacturer. Replenishment of oil and grease is only necessary after approximately 2 years of normal use, as the most important bearing points (motor bearings) have sintered metal bushes.

Bearing points and friction faces should be lubricated sparingly rather than generously. To prevent failure of lubrication, it is recommended to use the original lubricants stated below:

1. Wacker Silicone oil AK 500 000: Used for the cueing mechanism.

3. BP Super Viskostatik 10 W/30: Used for specific motor and mechanism points.

4. Shell Alvania No. 2: Used for other friction surfaces and gears.

When using different lubricants, chemical decomposition can often occur.