Fixing a Dual 505 Turntable (start Mechanism)

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Introduction: Fixing a Dual 505 Turntable (start Mechanism)

About: Dutchman in Cologne.

A few years ago my trust (and old) turntable started having problems switching on. Normally, moving the tone arm onto the plate or record will switch on the motor and the platter starts spinning. In my case this was not happening everytime. Sometimes it did switch on, sometimes it didn’t. Because I could nowhere find a real solution to this problem I decided to make this Instructable. In my search for a solution I found out that this problem happens very often with the different versions of the Dual 505 (505, 505-1, 505-2, 505-3, 505-4). I own a Dual 505 so pictures only resemble that version. I presume the other models just work and look the same for the bigger part, but I am not sure.

Most of the other solutions I found online would tell you to just move the tone arm back and forth a few times. Looking at the reactions in other forums this would only solve the problem for a short period of time. After that it would come back. Not really the solution I was looking for.

So I decided to take the turntable apart and take a look at the mechanism on the underside of the top plate. I found out that there is a small adjusting screw that controls how long (or how short) the tone arm will drag along a certain other part that presses the power switch.

Read the f-ing manual

After I found out about this, I stumbled upon an old service manual (you can find it as a PDF at the bottom of this intro) which also addresses this exact same problem. In badly translated english it reads:

Pawl
With the eccentric bolt E, the switch-way of the lever 142 can be adjusted.
Adjust the switch-way so that
a) the power switch will be switched on completely,
b) the segment 211 comes free from the pawl 186.

This is what we are going to do, but I will also show you how to open up the top-plate and where to look exactly.

Step 1: Opening Up the Turntable

First of all, when working on electronics, make sure you unplug the device. So take the turntable off of the power supply so you can not give yourself some electrical shock. I did the first time and it is not pretty. Now we can safely open up this little beast. You may or may not have a Dual that has a hinged cover. If you do, flip it open and you can lift the cover out of the two hinges at the back. If there is no dust cover you can (how surprising!) skip this step. After unplugging the next most important thing is to lock the tone arm into place using its clamp.

Now to make things easier (and lighter) remove the slip mat and the platter rom the turntable. Simply lift up the rubber mat and locate the metal locking that holds the platter in place. Twist this about a quarter turn and it will come off. Now you can easily lift off the platter.

Open Sesame

The top plate is connected to the bottom tray using two bolts. They can be easily loosened using a big flat screwdriver or even a small coin (I used my fingers). Just loosen the bolts, they cannot be turned out. Just turn them anti-clockwise untill you feel there is no more resistance.

Now on to the fiddly part. The bolts are hooked into place inside the tray. Press the top plate and the bolts down and pressing on the top of the bolt outwards you can feel that it slides out of the hook in the tray. Do this with both bolts and now you can flip up the top plate. Be aware of the cables at the back, so just flip it up and do not try to lift it or take it completely off.

Step 2: On to the Internals

Now that we have loosened the top plate and flipped it up, we are welcomed by all the electronics and a lot of metal hinges, arms, springs and prongs. Do not let this throw you off. We are just here to make a small turn on one of the little screws. Go ahead and gently unlock the tone arm and move it a few times back and forth. Observe how everything connects and works together. Move the tone arm to the center and see how the motor automaticly is switched off.

We are looking for the little eccentric screw (as mentioned in the intro as "Adjustment Bolt E") that I also marked out on the second pictre. I cannot really explain what it does, but if you turn it too far it either doesn’t release and presses the switch or it is released too soon and also never presses the switch.

In order to check if we turned the screw far enough and it does switch on the motor we need to plug in the turntable again and move the tone arm towards the center. I made a small video of what should happen if the screw is adjusted properly. If all is well you can now close up the top plate, tighten the screws and plug in that old beast. Put on your favorite record and rock out!

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    11 Comments

    0
    Deckchap
    Deckchap

    10 months ago

    Having fixed more than a few Dual 505 turntables and others, and many taperecorder decks let me start by saying that not one of my decks ever came back to the workshop unlike others I am sad to say. So now, to the Dual 505-1 and 2. Firstly, before you go undoing screws and altering settings note the following. These turntables were preset in the factory in Germany. They arrived well boxed with settings preserved. So, why is the motor not starting when the arm crosses the turntable? The answer may be simple and it has 4 letters...DUST. So first get a dust extractor spray. For example the 'aqprox Spray Duster. Insert the small plastic tube provided into its nozzle. Do NOT use a vacuum cleaner! Make sure the power is off and lightly spray clean the small lever held to the underside of the turntable by a spring clip that moves the push switch in the brown contact box that operates the motor circuit. Spray the push switch lightly also. Do not over spray and avoid any residue going in the motor circuit or on the turntable or other parts not mentioned here. You do not have to dismantle any parts. Spray all the clips that guide the lever that activates the switch in the brown motor contact box. Allow the residue of the spray to dry. No oils or additional lubrication is required. Now activate the pickup arm manually a few times, still with the power off and note that the small push switch in the brown contact box is moving into the box past where it previously did before you cleaned the parts mentioned. There is no need to force anything or change any settings unless ofcourse the manufacturer has forgotton to set the settings or someone has tampered with them, in which case a guide to the settings can be found in the user CS505-1 and 2 manual and parts list. On another point. Never change the speed from 33 to 45rpm when the turntable is in motion as this causes the drive belt to wear and leave residue on the inside of the turntable hub and on the speed switch lever. Select your speed first and then move the arm over your record. The only real issue with Dual 505-1 and 2 turntables that I know of occured with the motor circuit when the UK voltage was 240V. Now it is 230V. I have not found motor circuit problems since this change but it may be that I have been lucky. However, in consideration of problems experienced by others concerning over heating of components in the motor circuit you may wish to change the capacitors in the motor circuit if they are of the Rifa brand. Please read comments by others on this issue. Another issue concerns tracking weight. The recommended tracking weight for ortofon stylus DN149S is 1.50g and it is 1.50g for the DN165E also. This is within the cartridge ranges 1.25g to 1.75g. However, having balanced the arm with record on the turntable so the needle is slightly above it, you may find that after a little use the weight has become slightly heavier or lighter than when you set it. A gentle slight adjustment to the counter balance may be required. (make sure your bias compensator is at zero and your power is off before making this adjustment). Your stylus will be a spherical one so it is the bottom range on the bias compensator you need to use. Eventually, the mechanism will settle down. The balancing act takes patience but the sound results will more than justify it. Finally, when setting up your turntable use a spirit level on it to make sure it is level all round. Now sit back and enjoy your music.



    0
    JohannesB28
    JohannesB28

    4 years ago

    Hello, I also followed your instructions and it did not work. The
    screw is not moving up or down, but it moves left, right, backward and
    forwards.Whatever I think either the screw losses on thickness over time
    so that the mechanics don't work anymore or there is/was a plastic
    thingy which disappears over time.

    Solution:

    If the instruction above does not work for you. Remove first the spring and then the nut of screw(E).
    Then you have to find a small round plastic thing with a very small
    thickness which you can put over the screw (E), then follow the
    instructions above again. For the replacement, I tried several things,
    in the end, I cut a small piece of a dowel and used sandpaper to get to
    the right thickness.

    0
    Pdrummer
    Pdrummer

    4 years ago

    I have a Dual 506 tt with a mmc 10 E B&O stylus.
    I put a record on yesterday and music only came out of one speaker? I did a
    process of elimination since I have my DVD player & cd player hooked up to
    my receiver I put a cd in & music came out and both of the speakers so
    obviously it means that something is up w/ the Dual turntable. I then hooked up
    one of my spare turn table and it's working fine music out of both speakers. Then I took a needle from one of my other
    turntables replace it with the B&O needle and see if it is the needle or
    the turntable & again music came out of both speakers. I just want to know
    if anybody had this problem & think it's the needle? I wonder if the stylus
    is worth getting fixed?. Any other suggestionswould be great thanks..

    Pdrummer

    0
    AlexF254
    AlexF254

    Reply 4 years ago

    i dont have a dual 506 but i do have a 505 which i think have similar cartridge and shell connections. Apart from the switch problem these turntables suffer from contact problems in the cartridge shell configuration and i think that when you switched needles you could have pushed the cartridge enough to resume full contact to both channels. This was bugging me to the extent that i replaced the dual cartridge head which set me back 70 Euros - nearly 80 dollars

    0
    Pdrummer
    Pdrummer

    Reply 4 years ago

    Thanks AlexF254 I might have to do this which cartridge/ head did you buy

    Thanks

    0
    AlexF254
    AlexF254

    Reply 4 years ago

    You can check whether you have continuity from the cartridge contacts to the rca plugs using a resistance meter. If you dont. remove the cartridge together with the plastic cartridge contact plate and try to spray some contact cleaner on the connections. If you look in the cartridge shell you may see a small pcb with contacts and that is usually where the 'contact' problem lies. Also make sure that the pins are inserted correctly to the cartridge. good luck

    0
    Pdrummer
    Pdrummer

    Reply 4 years ago

    But I did get it working again

    0
    Pdrummer
    Pdrummer

    Reply 4 years ago

    well I took all the wires out cleaned up the terminals put it all back together I did have to re-solder one wire that went to the head shell that I cut, Next time I'll change the RCA plugs I think that might be it. Thanks

    0
    AlexF254
    AlexF254

    4 years ago

    I have followed the instructions to remove the top plate (thanks) and tried to turn the screw but it was too tight and anyway i have no idea what the screw has to do with the problem unless it is loose. What i found was that the lever mechanism was not going far enough to activate the micro switch (about 1-2mm too short) so i carefully applied some silicon spray to the hinges and moving parts and after moving the mechanism manually for a few times the problem was solved

    0
    AlessandroC99
    AlessandroC99

    5 years ago

    I've tried turning the screw every which way but it won't unhook the tonearm. What can I do?

    0
    flim
    flim

    Reply 5 years ago

    First of all: are you 100% sure it is the right screw? And second, try moving it in small increments. Start with quarter or half turns in one direction and see what happens. Them either continue in that direction or, if you notice the problem is getting worse, try turning the screw the other way around. Easy does it!