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:

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.

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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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    10 Discussions


    1 year 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.


    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.


    2 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..


    5 replies

    Reply 1 year 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


    Reply 1 year ago

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



    Reply 1 year 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


    Reply 1 year 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


    1 year 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


    2 years ago

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

    1 reply

    Reply 2 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!