Torsion Spring unwinds when cables are released from drum

Hello,

New here.  This is my first post, as I have run in to some difficulty in repairing my garage door.

First Problem
My garage torsion spring broke, and I decided to replace both springs.
The original torsion spring size 234 x 1.75 x 30.    I ordered the replacement exactly as needed but I received 
243 x 2 x 32. 

In hopes of making adjustments to winding the larger spring, I wound the springs 25 times.
It worked great for a few days without any issues.

Second Problem
Today,  one of the cables came off of the drum.   I managed to get the garage door in the down position
and while I was releasing the cable tension on the other drum, the entire torsion spring unwound.   

How or why is the torsion spring unwinding when the cable drums are loosened?  

When the door is manually raised the cables appear to slack as the door reaches the horizontal position
It appears the springs need to be wound a bit more.  

However, I don't want to attempt winding the springs if I can't resolve why the springs are unwinding.

Any help will be greatly appreciated,

Mahalo,

  
the springs and

I'm also new here... 

#1 Your springs are OK - same IPPT as old just longer cycle life (16K)

#2 Start with 7 complete turns (28 quarter turns) if 7-0 door, 8 / 32 if 8-0 door

Set LSLO cable drum first then right - wind springs - check balance

Just so you know cables are "holding" spring tension...that is why springs unwound when you released set screw on drum 

Be careful - take your time

Have a blessed weekend