i don't know if your scale was fixed or replace. Let me give you a little insight on the scales. Of course you know that it has a reader head. This reader head gets both the sine and cosine from the scale giving you a 360 circle in a scope. The size of that sircle is the amplitude of the Sine and Cosine. In other words how strong a signal. Over time components wear out, resisters diods etc. the signal starts to drop, by you removing the jumpers in the preamp board ,your amplifying the signal. for a while at least. but, if you removed all jumpers and still have a problem. You can always remove the scale, remove the rubber lips, clean the class, and take a look at the reader head. ok, on the reader head you will see an Emitter and reciever one on each end ,and the glass that runs through them, look at the reader head and you will se a 10k i believe resistor. remove and ohm it out. if its more than 5% off from 10k, go to radio Shack and get another one. solder it back in. and ,hopefully it works. i saved countless customers from spending 1700 for a new one with CT when all they purchased was a 30 cent resistor.
later people,peace.!!!!!!!!!!!!!!!!!!!