Tension Springs for Drive Cords?

[Geaney]

HI Paul, yes it's a 3028. I've used a spring I had lying around but the tension is not right so I can't be sure if this is why the drive slips occasionally. BTW, I'm also on the hunt for a glass dial - mine's damaged. I found a scan of the German version online but not the English one.

All help greatly appreciated.
Cheers, John