Is my Scott Parker tuned scale off?

[aahunt03]

This is what I am doing:
I set the scale up and zero it out by turning the knob at the bottom.
To verify the scale is accurate, I place the supplied check weight in the pan, and adjust the weights on the beam.
The scale does not balance out at this point. I have to adjust the leveling knob underneath the scale two or three full revolutions to get it to balance out correctly.

The scale used to be spot on and there was no discrepancy between zero grains and the check weight.
I have already cleaned all knife edges with alcohol and verified the scale rests on a perfectly level surface.
Any suggestions or am I doing something wrong?

 

[sandwarrior]

What kind of scale is it? On my RCBS scale the counterbalance weight (up near the pointer) was bent ever so slightly. It showed high until I tweaked it back.
Anyhow, that is supposed to be perpendicular to the beam.

 

[Bradu]

I was given a supplied check weight of 155.3 grains if I remember right and that was what I was suppose to set my zero to. If I checked to see what it did on 0 it would be off. I never understood why I was doing it that way so I bought check weights and set it to the weight I was dumping. I'm just a dumb mechanic but that made more sense than what he had me doing. I can't see why I would zero it that high when I was dumping 42 grains of of powder.

 

[SporterII]

Using your scale like a comparator is really how most mechanical tools work anyway.
Know that residue from powder can cause the pan to vary in weight I clean mine with soap and water and thing goes back to zero when level as it's last use.