I just got a couple of the Hi-Tec HS-50 servos.. I also bought a couple sets of gears in case I have a mishap.. I am wondering how i am supposed to open the servo to get at the gears.. The are no screws holding the case together... Does any one know how to open these?

From : Don Stackhouse

Instead of screws, the HS-50 uses little tapered pins molded into the corners of one case half, with matching tapered holes in the other half. Right next to each pin is a shallow rectangular recess on the outside of the case. Get a jeweler's screwdriver about .075" (2mm) wide. Insert it into the recangular recess, give a firm but gentle twist, and the two halves of the case will pop apart a little. Open each corner a little at a time, doing each corner in turn, so they all come apart more-or-less at the same time; if you try to pop one side out completely without doing the other corners too, you might bend or damage the plastic pins.

To put it back together, just fit the case halves back together, make sure all the gear shafts and case pins are aligned properly with their sockets, and press the case halves back together. It's really an effective system, both from the standpoint of engineering cleverness, and for manufacturing precision (as anyone who knows what it's like to manufacture precise press fits in plastic parts can attest!).

The gears themselves are also pretty straightforward. The output gear is a tight push fit onto the brass feedback pot shaft. It will come off with a firm, straight, steady pull. Note that there is a flat machined into the feedback pot shaft, and a matching flat in the bore of the output shaft gear. Make sure you get these aligned properly when you install the output shaft gear!

We have seen ONE case of a looseness in the fit between the flat on the shaft and the flat in the bore of the gear, which resulted in the servo developing a bit of a "mind of its own". It's similar to the infamous problem with the GWS clones, but not as likely, and not as severe. However, if you do encounter this, it's easy to fix. Just wax the feedback pot shaft (to make it easy to get things apart if you ever have to replace the output shaft gear later on), then put a TINY drop of 5-minute epoxy on the flat of the feedback pot shaft just before you press on the output shaft gear. The epoxy will fill any gaps between the flat on the feedback pot shaft and the flat in the gear bore, eliminating any play or drift.

Don Stackhouse
DJ Aerotech