Adapter for Walzenstecker | ADoS ZB

This is an apater for the historic german telephone and Telex connector Walzenstecker / ADoS ZB 27 using easily sourceable parts.

It is not a drop in replacement for the ADo ZB 50 wall connector and might not be as secure or safe as it.

Please make sure you know what you are doing when working with electricity.

Additional parts needed
 

• 4 x M3 Screw + Nut
• 3 x Pole Spring Clips
  ( the type used for locking two pipes together )
  • Width: 5mm
  • Thickness: < ~0.5mm ( this can vary as the slack is taken up by the screws )
  • Head diameter: 3 - 4 mm
• 1 x Battery spring contact
  ( flat metal with a bend hook shape )
  • Width: 5mm
  • Length: 20 - 25mm
  • Height: ~8mm
  • Thickness: < ~0.5mm ( this can vary as the slack is taken up by the screws )

Assembly
 

• Insert the pole spring clips into the three slots around the opening
  • Make sure the heads all point inside towars the opening as seen on the photos
  • If needed bend the clips slighty so they can align perfectly
  • The two clips that are next to each other will need to be compressed almost fully to insert them. I found hooking the end into the slot then compressing them against it and the sliding them down works best.
  • The last clip for the smallest ring should be pressed down as far as it can to make the spring stiffer and the locking more secure.
• Insert the battery spring at the bottom so that the highest part is at the center of the opening
  • I had minor unwanted bridging issues when printing. Clean out stray material and make sure the opening is free so the plug fits through
  • Do not bend this spring to make it stiffer as it will decrease holding force.
• Thread the screws with the nuts into the plastic until the metal springs are held firmly
  • The plastic should hold the screws tightly. Additional plastic and slightly undersized holes has be used to make sure they get enough grip
  • Sometimes the screws will push some plastic through, preventing propper contact. Make sure the pushed through bits are cleaned off to allow for contact.
    This has been almost entirely fixed in the latest version.
• After connecting yourwires to the terminals, screw on the cap if wanted.

Usage

If you need this you will already know how to use it for your application

For teletype use In a local / half duplex current loop I found connecting the single pole clip and the bottom battery spring works best. This is the way it can be seen in the photos.

For connecting i recommend ring connectors on the screws
Spade connectors can be used on the three snap springs. Additonal space was left for this use.

For mounting the inline M3 holes at the bacl can be used. They are the same diameter as the spring screws for a tight fit if needed.

The connection is relatively secure and allows for a fair bit of tugging on the connector before loosing connection. Strong movement may interrupt the connection.

Troubleshooting

Bad contact

This can happen because of too little holding force. If there is a significant gap between the plug and the socket plastic but you can push it in deeper to have good contact refer to Not enough holding force section.

If the plug is pushed in all the way and there is no contact check which spring does not contact.

• bottom spring
  • Check for plastic preventing the spring from making contact
  • Make sure spring resting position is close enough to the plug when fully inserted
• Clip Springs
  • Check positon of the head. They should align as seen in the images. Sticking put slightly from the ring. Bend them open or closed and move them up and down in their clamp untill aligned

If all clips make physical contact to the plug check continuity between the screw and springs. Small bits of plastic might be trapped and prevent propper connection.

Not enough holding force

• Check if the bottom spring has too much force pushing out the plug. If it does, bend it so it barely touches the plastic to have as little spring as possible.
• Check if the clip for the smalles ring makes contact with the prodruding wedge to increase spring tension.
  • To further increase spring tension bend this clip in a slight s-shape so it gets closer to the wedge