Tuesday, September 16, 2014

Trojan T28 Repair, Flap Servo

So, what do you do when you have a flap servo go out in your Airfield/FMS T28?  This is not a regular servo but the slow rate servo.

Well, if you're a normal person, you find a source for this special servo and order/buy another one.  But, if you're a cheap Dutchman like me, you fix it!

This video shows the failed servo.  When I first tried to move it, it was locked completely and did not move.  By the time I made this video, it freed up and appeared to be working OK, but I think you can see (even with the bad focus) that was not working smooth and was catching.

One good thing this video shows, is that the servo circuitry should still be fine.  It just needs new gears.

Here is the server just after popping it loose from the wing.

Here is  the servo with most of the glue removed and sitting next to the tiny Phillips screw driver tip that was needed for the tiny screws (better get your glasses prescription up to date).

You may be asking by now "How are you going to fix this broken servo?"  Well, it just so happens that I have the burned up servo from my front gear door repair, and this servo looks exactly the same (see the photo below).  If you read my blog post on this, you know that the a jamb caused the burned up the motor and/or circuitry.  Now this "donor" servo does not have the slow circuitry, but that's not what I need.  I just need the gears, and they should still be fine.  The broken flap servo should only need a gear or two replaced, as the circuitry is fine.

This below, photo shows the start of the tear down of both servos.

This photo shows the broken gears removed and set aside (on the right in the middle) and the gears from the donor servo (left) already removed and installed in their place.

There was one difference between the two and that was that the case screws from the original were slightly shorter that the donor screws.  The donor screws also had longer threads for a more secure bite.

Since a test fit showed that the longer screws worked just fine, I decided to use them in the repaired servo.

Below is a video of the assembled servo showing that it is now working just fine.  There's that focus problem again!

In this case, this repair saved me about $15 and shipping for a replacement servo.  Some times it pays to be a cheap Dutchman keep all of your old broken crap that most people would just through away.

Ya, another one down.  Still more to go.

Thanks for stopping by my blog.  Please feel free to post comments, good or bad, and be sure to come back and check for future posts.

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Mr. Clean