DP-4

   

 

H. H. MØRCH


Instructions

Contents of the packing

In the packing of the tonearm you will find the arm base in which the bearing is encapsulated in a heavy body. This is the link between the moveable part of the tonearm and the arm pillar, which is to be mounted in a bush in the board of the turntable.

Further you will find one arm tube according to the choice that you have had from literature about the tonearm or from advice of your dealer. There also will be 4 weights, finger lever with screws, knurled nut, hexagon spanner, and a syringe with silicone fluid.

The tonearm usually is supplied with the arm rest mounted on the pick-up lifter, but if desired a separate arm rest could be supplied instead.

Mounting the bushes

First it has to be decided exactly where to place the bush in which the tonearm is to be mounted. The center of the bush should be at a distance of 212 mm (8 11/32'') from the center of the turntable platter and there has to be room enough for the counterweight rod to move freely. The counterweight rod is having a rear overhang of 70 mm (2 3/4 ") as to the center of the arm bush. If separate arm rest is used, it should be placed so that the arm when resting on it is at a suit­able distance from the record.

The mounting template on the packing of the tonearm is showing the position of the arm base and the arm rest as to the turntable spin­dle. It should be noted that the position of the turntable spindle shown is just an example. In order to allow for the most convenient position of the arm base the turntable spindle could have its center anywhere on the arc shown.

Mark the center of the arm bush and check that the distance to the center of the turntable platter is 212 mm (8 11/32"). Then drill a 20 mm (13/16 ") hole with center in this mark. Also, if separate arm rest is used, drill a 10 mm (13/32 ") hole for the bush for the arm rest about 155 mm (6 1/8 ") in front the 20 mm hole.

Fastening the two bushes: In order to make it easy to adjust the height of the arm and the arm rest with the accompa­nying hexagon spanner, the small screws for fixing the arm and the arm rest should point to the right.

Then the arm base is fastened in the arm bush.

Mounting the cable to the amplifier

Put the plug of the accompanying tonearm cord into the socket below in the arm pillar. Try to avoid bending the cable too sharply right next to the tonearm connector. If the turntable has a floating sub chassis, the cable should not be restricted in any way, and it should be arranged in a suitable arc, so that it can not limit the free movements of the suspension. Remember that the ground wire should always be connected to the chassis (ground terminal) of the amplifier­. The chassis of the turntable may also have to be electrically connected to the arm bush.

Choice of weights and putting them on

In order to make it possible to balance all phono cartridges the tonearm is supplied with three counterweights - large, medium, and small - having the hole excentrically positioned and with a tracking force weight having a centrally positioned hole.

The weights that are to be chosen for balancing a cartridge depend on which arm tube that is to be used and on the weight of the car­tridge.

The weights to be used can be found in the below table (tf. means tracking force weight).

At first the counterweight/s is put onto the counterweight rod and then the tracking force weight. To put on the counterweight/s and to displace them along the counterweight rod they have to simultaneously be revolved to and fro.

Weight of counterweight in grams when using:                Counterweight size:                  Note:

Light arm tube

Medium

Heavy

Extra Heavy

 

 

“Green”

“Red”

“Yellow”

“Blue”

 

 

 

 

 

 

 

 

1.2-2.4

 

 

 

small only

1

2.5-6.5

0.5-4.3

 

 

small + tf.

2

5.2-7.6

3.0-5.4

0-2.2

 

medium + tf.

 

7.6-12.7

5.4-10.2

2.6-8.2

 

medium + small + tf.

2

9.0-9.9

7.0-7.6

4.1-5.0

 

large + tf.

 

11.9-21.2

9.9-15.4

6.7-11.3

0-4.8

large + small + tf.

2

19.0-21.2

17.0-19.4

14.0-16.2

6.5-9.0

large + medium + small + tf.

2

Notes:

1. Here the small counterweight is used as tracking force weight.

2. Here both the tracking force weight and the small counterweight are used as tracking force weights. Each of them gives 1/2 gram of tracking force when slid 1 indentation forwards.

With heavy cartridges or if large tracking force is needed the medium or the large counterweight should be used for adjusting the tracking force as well. The medium counterweight gives 1.2 g and the large counterweight gives 2 g when slid 1 indentation forwards.

Thus a certain tracking force can be obtained by sliding more than one weight adding up their shares of tracking force.

Refilling the silicone fluid

The accompanying syringe contains 0.5 - 0.6 ml of silicone fluid. At first the pick-up lifter should be filled in. Pull the black piston out of the lift cylinder and place it in a completely clean place. Then inject 0.1 ml (10 units) of the fluid behind the shaft inside the lift cy­linder. When doing this the lift handle must be in "lowered" position. When the fluid is injected, the tip of the syringe is "wiped off" on the shaft, and the syringe is pulled up with a little jerk there­by preventing the fluid from getting in touch with the walls of the lift cylinder. Do not put the piston back into the lift cylinder until the silicone fluid has merged down to the bottom of the cylinder, and hereafter the piston must not be pulled up again, as the silicone fluid would then easily stick to the walls of the lift cylinder. If this happens the piston will "go down" much too slow.

Thereafter silicone fluid is to be filled into the well of the tone arm. This is done through the hole, which is seen in the Plexiglas on top of the arm, when the arm tube is not on. The tip of the syringe can just reach the well through this hole, if the arm base is tilted backwards. Inject 0.2 ml (1/3 of the contents) of the silicone fluid into the well and carefully “wipe off” the tip of the syringe on the edge of the well, before pulling the syringe up with a little jerk. The Plexiglas over the well must not be unscrewed. If there is too much fluid in the well, it can be taken up with a drinking straw.

Mounting the cartridge

While the silicone fluid is merging down to the bottom of the well, the cartridge can be mounted on the arm tube together with the ac­companying finger lever. If possible, use the accompanying aluminium screws. Provided that the tonearm is mounted, so that the distance from the pivot to the center of the turntable is as indicated on the mounting template, the position of the stylus - to obtain correct overhang - should be: with standard armtubes right under the front edge of the black plane of the armtube - with PRECISION armtubes 4 mm (5/32”) behind the front edge. Also the cartridge should be in parallel to the said black plane. Carefully push the terminal jacks of the wi­res unto the pins of the cartridge with a pair of tweezers. Do not force them too much and also see that you are not squeezing the thin wiring too hard. Red and green are signal and ground of right channel. White and blue are signal and ground of left channel. Then fasten the arm tube on the arm base with the accompanying knurled not, which should be tighten­ed well with two fingers. Check that the overhang is correct - 18 mm (23/32”) - and ad­just if necessary.

Adjusting the tonearm

First make a coarse adjustment of the weights. The tracking force weight - and where marked 2) also the small counterweight - should be back at the end of the counterweight rod, while moving the coun­terweight/s backwards or forwards until the arm tube is balancing in about horizontal position and rotating the counterweight so that the underside of the cartridge is parallel to the record as seen from the front.

Apply tracking force by sliding the tracking force weight and may be also the small counterweight forwards. Both of these weights will give ½ gram for each indentation that they are moved forwards. Thus toge­ther they will give 1 gram.

If one of the counterweights is going to be used to apply tracking force, the tonearm should be balanced with the weights arranged in such a way that there is room enough to move the counterweight in question.

It is an advantage to use as large or as many counterweights as pos­sible.

If by coarse adjustment of the weights it appears that the counter­weight can not get far enough forwards to obtain balance, the tra­cking force weight can be slid forwards until balance is obtained. This place then will be zero point for the tracking force calibra­tion. If the distance from here to the counterweight is not large enough to give the correct tracking force a smaller counterweight should be used.

The height of the tonearm now should be adjusted. With the stylus resting on a record the arm base is moved downwards or upwards un­til the arm tube is in parallel to the record, and the arm base is turned so that the pick-up lifter can always support the arm tube. The screw in the arm bush then is tightened with the accom­panying hexagon spanner.

Now make a fine adjustment of the weights by repeating the procedure that was used at the coarse adjustment. It is the easiest, to see when the stylus is hanging in level with the record, if something such as the small piece of foam rubber (which was jammed in the arm base when it was in the packing) is placed between the pick-up lifter and the antiskating spring, so that the string attached to the antiskating spring is not rotating the tone arm.

If the arm rest is mounted on the pick-up lifter, it should - when adjusting the position of the arm base - be considered that the arm rest should allow the arm tube to rest at a suitable distance from the record.

The height of the pick-up lifter is adjusted so that the stylus is about 4 mm above the record, when the pick-up lifter is in "raised" position.

If separate arm rest is used, it is adjusted in a height, so that the arm tube just rests on it, when the pick-up lifter is in "raised" position.

Antiskating

The antiskating force is adjusted with the little black handle next to the pick­up lifter. The amount of antiskating force required depends on the tracking force and the shape of the stylus. Thus no calibration is possible.

Coarse adjustment can be done with the stylus running between the grooves next to the label of the record. Correctly adjusted, the stylus should move slowly towards the center of the record.

Fine adjustment could be done by reducing the tracking force a little whilst listening to a critical passage. If for instance distortion occurs in the right speaker, the handle should be turned clockwise. (The best result is obtained with a test record). The adjustment is not critical. It is better giving too little than too much antiskating force.

The range that the antiskating handle can move, will cover most cartridges. The tension of the spring, however, can be altered by loosening the screw in the center of the round black pulley. By rotating the pulley with two fingers, you can set to a new tension.

Special about PRECISION arm tubes

PRECISION arm tubes are supplied in "red" and "blue" versions only. They have a wide and very precisely ground mounting plane to assure a good mechanical contact to cartridges that have a similar large and accurate mounting plane. The mounting plane of the PRECISION armtubes are 4 mm (5/32”) longer than the standard ones in the for­ward direction.

Special about 12” armtubes

In the section Mounting the bushes it is described how the position of the 20 mm (13/16 “) hole is found. For 12” armtubes the distance from the center of the hole to the center of the turntable patter should be 294.1 mm (11 19/32”).

Overhang of the stylus should be 13.3 mm ( 17/32”). If the arm bush is mounted exactly at above distance from the center of the turntable platter, the stylus should be positioned just under the front edge of the black plane of the arm tube.