Digitising the Märklin turntable 7286

The Märklin digital turntable decoder (7687) is meant to work with the 7286 turntable but it is horrible. The decoder tries to memorize the positions of the connected tracks and this needs to be refreshed periodically and this requires laborious 'programming' to tell it where track positions are. Even then the current that it provides to the turntable seems to be wholly inadequate - causing me to dismantle and service my turntable a number of times until I worked out that it ran just fine using the analog controller. Any disturbance to the movement seems to make the 7687 module go to sleep and it needs to be 'rebooted' .

I therefore decided not to drive my turntable using the 7687 decoder. Since I am using a PC to control my layout I decided that it would be simpler and more reliable to use a simple k84 type module to control the turntable. These pictures show how I did this.

The manual controller that comes with the turntable provides the plug interface to the turntable and a rather pathetic direction knob and on / off button to stop and start the turntable...

open up the case...

and note the bridge rectifier. We use this rectifier so simply desolder the 4 legs of the rectifier...

I positioned a Viessmann 5213, the rectifier and the turntable plug on a wooden base..

and wired it up as can be seen in the picture. 2 of the 4 switches are used to reverse the polarity of the DC current produced by the rectifier. A third switch is used to switch the stop/go signal for the turntable to be the same as one of the motor polarities. One rail plug of the turntable plug is left free for a s88 port to detect occupation or it can be grounded also. All the new module needs is one ground, one digital and one power supply to be connected. I suggest that you run the yellow power supply through a manual override switch. You can also connect an optional s88 line.

Here is the schematic I use in my software to define the k84 addresses to use for the turntable.

I used a spot of hot glue to hold the bridge rectifier in place.

I plugged it all in, added some lines of code to the program and it all works !

Here is a comprehensive description of how the Märklin 7286 turntable works.