Servo case replacement procedure....

In the FWIW column, I no longer repair servos. Except for throttle, all my servos are the 1/4 scale variety and most run $90 or more apiece. Even so, the cost of dumping an expensive giant because of a questionable but repaired servo is a whole lot more than the "cheap insurance" price of a new servo.
If you're _sure_ the electronics weren't damaged it's simple. If the electronics were damaged don't bother.
If you just gotts to repair the thing, find another good servo (any standard Futaba servo will do and will have the same gear layout as the S3003; S48, S148, etc.). Use the known good servo as an example of the gear layout.
The only alignment is the output gear which has a stop tab on the underside. That tab needs to be centered between the case stops when the pot is centered. Likewise, the output gear lower shaft must engage the pot correctly.
Otherwise reassemble per the gear arrangement in the known good servo.
OTOH, the gear set only goes together one way that works, so plug and play 'til you get it right. Just don't get the output gear and pot misaligned, because if you apply a signal with the gear and pot misaligned the output gear tries to drive past the stops and something breaks.
To find the pot center point, reassemble the servo minus the output gear. Apply a signal from a receiver and center the associated transmitter stick. Manually (with a non-conducting screwdriver or 'twiddle stick') turn the pot which ever direction is needed to stop the servo motor; that's the center point. The motor and gear train should stop and stay stopped. Move the stick one way or the other and the motor should run; move the stick the other direction and the motor should run the opposite direction. Release the stick and the motor should stop. That is, once you've got the pot centered. Holding the stick in one direction or the other will make the motor run continuously because the feedback signal from the pot is not changing.
Reinstall the output gear and re-test.
Be careful not to strip the threads in the new case (it's obvious when the screws bottom out) and don't misplace any o-rings ( . . . can't remember if the S3003 has o-rings or not . . . the 1/4 scale versions have 'em . . . )
Servos go back together with very little force. If you find you're having to use any appreciable force to get the case back together, >>>something is out of position

John Did you break just the top, or the whole case. If you broke the case, you might have done some internal damage. Anyway, here's what I do: CAREFULLY remove the top of the servo by first removing the screws and then, pressing down the servo output shaft, working the cover up. This usually keeps the servo gear train intact. With the now exposed servo oriented so the output shaft is on your left, remove the gears one at a time, placing them on a clean part of your workbench in two columns, one left and right, in the order that they were removed. (Put the first gears removed farthest away from you.) Inspect each gear, you might want to pick up a small tube of Lubriplate. Re-assemble in the same order, paying particular attention to the pin that located the gear train on the right side. When everything is lined up, the cover should fit down without any binding. As far as the rest of the case goes, once the cover is removed, the bottom cover should come off and everything can be removed out the bottom. Good Luck Bill

Thanks guys,
This was a brand new servo damaged on its first flight. The application is the release mechanism for an R/C skydiver, so it's not too critical. BTW, on the first jump attempt, the skydiver (mounted on top of the wing) caused the jump plane to crash due to a blanked elevator which drastically (!) reduced pitch control :(.
John
John Morley wrote:

Actually, the S48, 148 parts won't fit. The S3003 shares gears with the S3004 and the Tower TS53. If the case top is damaged, just buy the ball-bearing case update. You'll end up with a better servo at little extra cost.

refer to scroll down to "Servo & TX alterations, calculators, clonepacs, make an ESC or winch, FAQ." [under radios] where several sites have detailed colour pictures. e.g. for a quick written fix visit one of the Hitec FAQ pages = regards Alan T. Alan's Hobby Web Links

Then what did you mean by "(any standard Futaba servo will do and will have the same gear layout as the S3003; S48, S148, etc.)"? That's how I read it.
Jim - AMA 501383

[ . . . sigh . . . ]
_try_ to read the >entire paragraph< . . .
G'head. _try_.
I know your attention span is shorter than that of a gnat, but try to make it through the _whole_ paragraph.
All the way through the last sentence.
Where it says "Use the known good servo as an example of the gear layout."
Cheers, Fred McClellan the dash plumber at mindspring dot com

Roughly once a year I dump the twit filter. Most twits are gone by then.
Some never seem to be able to deal with the written word, in this a most decidedly written word medium.
No sooner do I have the twit filter purged than some new twit, or some old twit who simply cannot learn, chimes in.
Bye, now . . .
Cheers, Fred McClellan the dash plumber at mindspring dot com

Lets see, Your advice to a guy who needs to put a servo back together is for him to take another apart which is kinda-like the one he already can't figure out. In taking it apart, he stands a chance of having the gears on this one fall out just like before. You don't warn him that when taking a servo apart that the gearshafts might stay with either the servo top or the case. He now stands the chance of having two different servos apart that he can't figure out. Now, who's the twit?
Jim - AMA 501383

Moral of story Fred! Don't dump your twit filter. That or learn to accept others point of view and realize you way isn't always the only or best way.

Jim, You observation is right. I have been watching this and wondering when he would wake up and realize that even a ghod like him must give good instructions. I guess it wouldn't be so bad if he was anywhere near as competent with the English language as he swears to be. I am beginning to suspect that the lofty know it all advice this bunch of crazies is getting comes from a mr. perfect who has never done all the things he preachers, er I mean lectures on. As for you last question, you should already know the answer to that!
Jim Branaum AMA 1428
Six_O'clock_High Target snipped-for-privacy@Guns.com

Differing points of view never will have been the issue and you should know that. Ditto for learning new or better ways to do things. Never ever EVER said I knew the one and only way to do ANYTHING.
I have no problem with the expertise of most of the residents of my twit filter; in fact many have more experience than I ever will have had.
I do have a problem with their _attitudes_, which is why they get dumped into never-never land.
Case in point : had the latest twit (e.g. the most recently re-added twit) admitted he mis-read the subject post that would have been that.
No, he's got to haul out the 'tude. First time out he read it wrong, second crack he takes at it, it's my fault for writing it wrong.
Go figger . . .
N'other jerk _starts off_ by allowing as how he doesn't know what it is he's looking at on my lowly web site, but whatever it is it's a "mess" and he's >got< two of 'em.
He's got two, can't recognize the one he's looking at, so it's a "mess".
You tell me, izzat 'tude or what ?
Last go-around with said jerk had everything to do with him blaming me for something someone else wrote; seems he's a bit short in the literacy department. Worse, that jerk is _always_ baiting, denigrating the efforts (or equipment) of other modelers, insulting their _families_, etc. 'nuff of that crap.
Dunno 'bout you, but I'm not willing to waste time on 'tude toads.
I don't care if the toad plays kiss-and-makeup so he can finally snag a moderator slot on a decidedly minor mailing list.
He's now a permanent resident of my bit bucket no matter what he kisses. Cheers, Fred McClellan the dash plumber at mindspring dot com

And what about the TUDE we're seeing right here Fred? Think your TUDE might have something to do with it?
Consider what YOUR TUDE tells the world.

I would hope it tells the world that I am only willing to put up with just so much harassment, and should some twit exceed my limit I have every right to opt him out of my downloads.
Which you have now done.
Bye bye again, Kevie
Cheers, Fred McClellan the dash plumber at mindspring dot com

Good grief, Fred-
You had me baffled for a while, discoursing about twitdom with its reigning icon in this forum. I feel better about your sanity now.
Abel

What it tells the world is that you are the type that MUST have the last word. Why else would you announce to the whole world that you are putting someone in your "twit" file? Just do it and save the bandwidth!
Randy (Soon to be in your twit filter)

Well now! That was easy. Let's hope he sticks to his word! This time! For a change!

Don't worry about it Randy. Fred always goes into these twit rants whenever someone holds a mirror up to his face.