My first post here and I'm afraid it's a plea for help.

Does anyone have any experience of changing, or at least removing, a counterbalance spring from a devere 504 or 5108? Or perhaps a copy of the service manual of either to consult?

I have converted my bench 504 to a 5108 using my recently acquired floor standing 10x8 and all is well so far but it's obvious that it needs to have the correct spring in the column to work as it should. It's not clear to me at the moment how I should proceed though. Anyone have any ideas before I take them to bits again?