|Some servos are very expensive,
so when you break one, it's nice to be able to fix it yourself. Most servos
have gears and servo cases available. This can save you a lot of money. It's
nice to know what you're up against when you crack the case open. I hope
Replacing the gears is the easiest repair by far. Just take the top off, carefully remove the gears, clean up and reassemble.
Replacing the case is much more complicated. Some of components are a little difficult to remove, but it can be done. Typically, it's only the top that needs to be replaced. Be careful not to ruin the rubber seal when you remove the top and bottom of the servo.
We will have servo grease soon, if you want to really do it right, but I got by for years by picking the chunks out of the old gears and reusing the grease that was in the servo originally. I always tried to account for all the missing teeth. Of course you have to be careful. One little chunk of plastic can ruin your day.
The gear train.
This is what you see when you pry the bottom off a 9253.
The white material appears to be a white silicone sealer. I would think that it would be wise to renew this when you reassemble the servo after changing the servo case. Don't just go down to the hardware store and buy some bathtub sealant! Some silicone sealers are very corrosive. You need to get one that is designed for electronics. Look at the ingredients and stay away from anything that has acid in it. More on this later.
This is the top of the servo after all the gears are removed. Note 9151 is molded into this case.
This is the top of the replacement case for the 9253. Note 9203 is molded into the case. Quite a few cases are used for more than one servo model. However, they aren't necessarily interchangeable across models. For example, the 9203 case might not work with the 9151 servo.
The gears below are available separately from the online store.
9253 1st Gear
9253 2nd Gear
9253 3rd Gear