For anyone who is doing this for the first time a few tips.
Once you have the guitar open, you block the saddle based on adding and subtracting load on the fretboard. For example;
* E to Eb with 9s is subtracting weight from the saddle, in this case the saddle will sink into the cavity. You want to block the spring side of the trem.
* E to E but with 10s you are adding tension to the saddle. This will raise the trem out of the cavity so block the trem at the none spring side.
* I blocked the spring side with a stack of 5 pences. As the spring side was quite tight I added a stick of plastic to the coins and then taped them together, this came in hand why they shifted and I had to move them.
* block both sides of the centre spring to ensure the trem does not tilt.
* I blocked the none spring side with whatever I could find fitted as long as it won't compress under pressure.
Here was the point to my question as it fell between the cracks of point 1 and 2:
If I change from E using 9s to Eb using 10s, am I adding or subtracting tension?
As I was replacing each string one at a time and had no way of knowing , I found I blocked the saddle on the spring side which was fine, but as I tuned the strings it started to rise. I then loosened up and blocked both sides of the saddle so it sat flush and tuned the guitar to Eb.
This is the best bit of information I found that was a "aahhhh" moment for me, when you are near the end of the process tune with the screws in the cavity, not with the pegs!
Here was my process using the example of going from E with 9s to Eb with 10s:
* remove the locking nuts
* tune the guitar to E (or so the saddle is level) with the tuning pegs
* block the saddle at the spring side both sides of the centre spring so the saddle is level.
* replace each string one at a time
* check the bridge is still level.
* once replaced block the other side of the saddle so the trem will not rise when tuned. (if you are going from E to Eb with the same gauge string you will not need to do this)
* tune the guitar so it is perfectly in tune
* stretch the strings and retune.
* put the locking nuts back on
* fine tune the guitar from the trem.
* remove the block on the none spring side
* remove the coins from the spring side.
Now the guitar will be out of tune and the saddle will rise but don't reach for the tuning pegs or the trem tuners.
Sit with the guitar in the playing position; do not do this part on a bench or laying flat as gravity will cause the bridge to sink a little. Tune the guitar using the two screws holding the metal plate the springs attacbh too and not the tuning pegs.
Now with a screw driver start to tighten the 2 screws in the cavity that the springs are attached too. Do this evenly as you will find the low E takes a while to tune and will suddenly shift a few cents when you tighten the high E side spring. It is also key to ensure that the plate the springs are attached to is not lobsided, keep it straight and parallel to the cavity wall.
Once you are in tune stretch the strings and tune again that way. Once you are in tune the trem should level.
Additionally I took the locking nuts back off, tuned and hung the guitar for a few hours to let the strings and neck settle. Did some recording last night, a few dive bombs and it went straight back into tune..
I hope this helps someone out there.
Mike
