2nd string lower problem

[Jason Lynch]

Thouht I'd put this here as well as the US forum. Perhaps someone might have some ideas?

I have a BMI SD10 that I bought from Lee Jackson in 2011.
So, having taken a look underneath her a few weeks ago, I was greeted by a collection of dirt and gunk in the changer, so decided to strip her down and clean the changer up. I wanted to change my copedent slight so Thought I'd kill two birds with one stone, etc!
Anyhow, with a minimum of hiccups she's back together and tuned and playing fine EXCEPT: I'm having trouble tuning the lower for my second string which has a half stop at D, using the pull rod for string nine.
I've just finished trying to tune this in again, and managed to get it close enough for my ears, only to find that the 2nd string now won't return to pitch.
Took another look underneath and found the spring wasn't pulling it back to the stop bar, so I fitted a stronger spring.
Now, when I engage it, it lowers to D, then lowers a tad and starts raising back towards C#. Now I'm really puzzled.
Does anyone know why this is happening? If you push on the lowering arm with a screwdriver, the string lowers a tone and more, so whats causing this issue?
Thanks guys and gals.
Jason

[Zebedee]

http://bb.steelguitarforum.com/viewtopic.php?t=254728
Scroll to the bottom of the thread to see my diagram and explanation of the problem.

[henry]

thanks for that Richard, great explanation of something I've struggled to understand

[henry]

sorry to hijack your thread Jason but anyone ( Richard ) got any suggestions on how to fix a raise that is not returning to pitch?

[Zebedee]

Henry,
It could be any number of things, ranging from a helper spring that's too strong (if there's a helper spring fitted), cross-shafts that are too tight, a pedal /lever that needs lubrication, pull rods binding on each other, a lower return spring that's adjusted with too much tension (if it's your all-pull guitar).

Put some photos up of the undercarriage so that we can get a better idea of what's happening.

[henry]

cheers Richard, I'll go and investigate all those things. Yep it's all pull.
I'll get some pics..

[Will C]

I'd go with Richard's explanation, that diagram in the thread he referred to is very clear. I encountered this one myself about three years ago when experimenting with spring rates on that old Marlen that I fitted an all-pull changer to. There has to be a good match between the string characteristics and the weight of the return spring. Fortunately I was able to see what was happening and got my spring-maker to re-wind the springs for me.

[Jason Lynch]

You have a spring maker...?

[Jason Lynch]

Well that sorted it.
Thanks to Richard, I steered clear of a stronger spring and removed the changer again!
Lo and behold there was a broken washer on finger number two, which I replaced last time I stripped it down. I decided against trying to file or sand another washer to thickness, and left that one off altogether. And it works a treat!
Thanks all.