Garage door repair

[Clint]

Hello all As per title. The outlaws garage door is broken. To start one cable snapped leaving the door hanging to one side and jammed in the opening..this is where I squashed my finger trying to force it.
Anyway,the only way I could get it to drop square was to cut the other cable which I know was not the correct thing to do. I should have tried locking off the spring but it's done,so all tension is gone. Door is now back on the roller tracks and square but can't really be used.
I've researched replacing the cones and cables etc,tools required etc and can buy the lot Inc tools,punch and tension bars for £25 specifically for the door,it's a Henderson Merlin pre 1982.
I've watched all the YouTube I can find. The only thing I'm struggling to understand is retension of the spring which sounds like it can be dangerous!
Any experience out there please?
Cheers!

 

[Rodcx500z]

I've watched all the YouTube I can find. The only thing I'm struggling to understand is retension of the spring which sounds like it can be dangerous

Yes they are as my mate found out after being knocked cold and spent 3 days in hospital, be careful

 

[JockyBrewer]

When I last had to replace a garage door cable I was also intimidated by the spring.

I called out a pro who attached the cable to the spring mechanism, threaded it through the pulleys and then grabbed the loose end with mole grips and pulled it in to place. He made it look easy.

 

[LeeH]

Is it the type with there all long pre tensioned spring? These store a lot of energy, accidents happen.

 

[Clint]

Got a spring across today top. There's no tension in it now,I think,as I cut the other cable which was still under tension.

 

[Clint]

It's a spring wrapped around a spindle which has cones on the ends the wires wrap around when the door is raised. The spindle can be locked off with some supplied pins while the spring is loosened via two grub screws and wound back with two bars.