Encoder Problems

I was working on tuning the servos on a retrofit I am working on, and one of the servo encoders is acting flaky. It seems to work OK at lower speeds, but when spun faster it starts to drop counts at more than a few hundred RPM. I double checked all of my connections and switched motor positions (problem followed the bad encoder). What is the possibility of being able to dissasemble the encoder cleaning it up, put it back to gether and getting it to work or is that not likely to work? The unit in question is an old Renco part. To take it appart I would have to desoder the leds in order to open it up.

I don't think they are more than 10 yrs old.

Does it have any adjustments? Sometimes older encoders have gain adjustments (potentiometers)
that affect the quadrature accuracy (90 degree phasing).

Sometimes encoders go bad from dirt buildup. A Qtip dipped in 99% Isopropyl alcohol can be used to clean the wheel, but cleaning the LED and resolver plate will require disassembly.

I can't even get to the wheel without disassembly on this one.

I was able to fix it. desoldered the LEDs, removed the wheel and cleaned it and the pickups with a cotton swab and denatured alcohol. The whole inside of the thing was covered with a thin sticky residue. Put it back together and with a small amount of fiddling was able to get the commutation working.