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Thread: S-Tech 50 HELP

  1. #1

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    S-Tech 50 HELP

    I have an S-Tech 50 in my 180 that is driven by an Aspen Pro with GPS Steering and other Nav. magic provided by a Garmin GTN650 in my 180. This last couple of flights the auto pilot would heading wander every now and then when coupled to the GPS but it would always resume normalcy after I disconnected it and re-engaged it.

    This last trip it did the same thing on the way and then on the way home it promptly wondered a bunch so I switched to heading bug steering on the Aspen thinking the GPS was wonky and it wondered there as well then croaked altogether and the indicator went dark and won't relight or go through the test cycle.

    I ended up hand flying an 8.2 hour trip in ugly conditions so HELP! I've got a couple more big trips coming up in two weeks. I called my normal shop for all things magical and he asked about the turn coordinator which seems fine (no flags or excessive noise) but unfortunately he's slammed for 6 weeks so he suggest I unplug it clean the plug and try again. I peaked under the dash and it is plugged in so I'm going to give it the old Maytag try this evening and see what happens, any other suggestions?

    Thanks,

    Kirby
    Remember, These are the Good old Days!

  2. #2
    behindpropellers's Avatar
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    Kirby,

    Does it wander on Altitude also?

    The issue with the servos is that they get carbon buildup. I cannot find the document, but you need to cycle the servo from stop to stop to remove the carbon on the brushes.

    Tim

  3. #3
    behindpropellers's Avatar
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    "Often the cause of this condition is wear in the D.C. Motor brushes creating carbon buildup on the commutator. In extreme cases this can be detected by measuring the resistance across the motor leads (Pins 3 & 4) with a digital ohmmeter. 12 volt motors should show a resistance of 3 to 4 ohms. 24 volt motors should show a reading of 8 to 10 ohms. If you see a reading 50% higher than these, that would indicate a high starting voltage problem. NOTE: A normal resistance reading does not preclude a motor problem as the culprit. An ideal starting voltage would be equal to or less than 1.5 volts for a 12 volt motor, and equal to or less than 2 volts for a 24 volt motor.

    In some cases these symptoms can be improved or eliminated by performing a servo brush seating procedure. This can be done by applying full aircraft voltage to the motor leads and allowing the motor to run for 4 minutes in both directions. Since the motors seldom see full rated voltage, the increased speed will often break the carbon glaze free from the commutator and the brushes will seat uniformly. This procedure is most easily accomplished through the computer connection utilizing the 9524 break out box. Jumper the motor leads to A+ and ground leaving the AP computer unplugged (AP Master Switch On)."
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  4. #4

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    Quote Originally Posted by behindpropellers View Post
    Kirby,

    Does it wander on Altitude also?

    The issue with the servos is that they get carbon buildup. I cannot find the document, but you need to cycle the servo from stop to stop to remove the carbon on the brushes.



    Tim
    No Altitude is rock solid. Would servo issues keep the panel controller from lighting up, it won't even self-test. Couldn't find a popped breaker but still looking...
    Remember, These are the Good old Days!

  5. #5
    wireweinie's Avatar
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    Which indicator went dark? Have you powered the system up after it's cooled down overnight?

    Web
    Life's tough . . . wear a cup.

  6. #6

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    Quote Originally Posted by wireweinie View Post
    Which indicator went dark? Have you powered the system up after it's cooled down overnight?

    Web
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    Nobody home, I cycled the breaker. Should be all lit up, switch is in test mode.
    Remember, These are the Good old Days!

  7. #7
    wireweinie's Avatar
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    Reach in there and grab ahold of the connector. Needs to be fully seated. Also check voltage on both terminals of breaker with system switched 'ON', should be no difference in voltage. Use the meter and check for ground connection. Loose ground = bad power input symptoms. Also check for power across that stand alone switch. If everything checks out there, then go ahead and panic.

    Web
    Life's tough . . . wear a cup.

  8. #8

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    Found a popped breaker (also labeled AP) and reset, proofed power to and across the switch in “on” position (24.6v). The unit does not begin the test (all annunciations lit) but does light up the back lighting and then pops the breaker after about 30 seconds.

    Wide spread panic now setting in...
    Last edited by OLDCROWE; 01-28-2019 at 11:19 PM.
    Remember, These are the Good old Days!
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  9. #9
    FdxLou's Avatar
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    Kirby
    Looks like you need to start brushing up on your stick and rudder skills!
    Lou1
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  10. #10
    wireweinie's Avatar
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    Quote Originally Posted by OLDCROWE View Post
    Found a popped breaker (also labeled AP) and reset, proofed power to and across the switch in “on” position (24.6v). The unit does not begin the test (all annunciations lit) but does light up the back lighting and then pops the breaker after about 30 seconds.

    Wide spread panic now setting in...
    OK.
    Next, disconnect the control head and turn on the power. If the breaker still pops, there is a short in the main harness. If it does NOT pop, plug the control head back in and disconnect all components connected to it, like servos and D.G. Turn power on and check the breaker. If it does not pop, plug one item in at a time and see which one pops the breaker.

    Web
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  11. #11
    aktango58's Avatar
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    Sad you did not teach one of your children to fly, so you could have them help with the long trips...

    Oh, wait, she did learn then moved on to find a life in aviation design and manufacturing!!!

    Wish I was there to help you fly it. I bet if you called the local FBO there is an instrument rated pilot trying to build time that would join you on the long trip and help you just to get the hours in their log.

    Don't let the blue smoke out!!!
    I don't know where you've been me lad, but I see you won first Prize!

  12. #12

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    Kirby call STEC their customer service and tech support is great, had a couple issues with the Bonanza and they took there time to walk thru possible solutions.
    I spent most of my dough on booze, broads and boats and the rest just wasted ! - Elmore Leonard

  13. #13

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    Well it’s not the harness and the turn coordator is on a separate breaker, have a call into S-Tec Support waiting on a call back for some guidance of options.
    Remember, These are the Good old Days!

  14. #14
    wireweinie's Avatar
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    So the breaker only pops with the control head plugged in? Even with the servos unplugged?

    Web
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  15. #15

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    Quote Originally Posted by wireweinie View Post
    So the breaker only pops with the control head plugged in? Even with the servos unplugged?

    Web
    The control head won't even show a light when you give it power, ran out of time... will unplug the servos this evening.
    Remember, These are the Good old Days!

  16. #16
    wireweinie's Avatar
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    So right now you have back lights but nothing else? Is that correct?

    Web
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  17. #17

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    Quote Originally Posted by wireweinie View Post
    So right now you have back lights but nothing else? Is that correct?

    Web
    Yes
    Remember, These are the Good old Days!

  18. #18
    wireweinie's Avatar
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    Double check the ground for the control head. Then unplug all the servos/components. But my feeling is that you may have a control head failure.

    Head between the knees . . . deep breaths. . .

    Web
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  19. #19

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    Does anyone else have an airplane that monitors your bank balance?
    Remember, These are the Good old Days!
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  20. #20
    wireweinie's Avatar
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    See, all the newest ones do that digitally. Only the old ones use steam gauges to drain the balance.

    Web
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  21. #21

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    Talked with S-Tek, and am hadded to Autopilots Central this morning at TUL for an evaluation of the roll servo and they are going to pull the head for service and send me on my way untill the parts get back from S-Tek... so hopefully fixed before my long trip mid next month.

    Thanks for the help.
    Remember, These are the Good old Days!
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  22. #22
    wireweinie's Avatar
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    Let us know what you find out.

    What led you to getting the roll servo checked out?

    Web
    Life's tough . . . wear a cup.

  23. #23

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    Quote Originally Posted by wireweinie View Post
    Let us know what you find out.

    What led you to getting the roll servo checked out?

    Web
    Just back from Auto Pilots Central after describing what it did, S-Tek said 90% likely the servo failed and took out the on board fuse in the controller and maybe a transistor or two. APC tested the servo and sure enough... once I got it in their shop the manager said no worries we’ll pull the servo order the part, pull the head and test it and repair hear and if they have the servo in Texas we’ll have you out the door Thursday or Friday.
    Last edited by OLDCROWE; 01-30-2019 at 12:39 PM.
    Remember, These are the Good old Days!
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  24. #24
    SteveE's Avatar
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    Quote Originally Posted by OLDCROWE View Post
    Just back from Auto Pilots Central after describing what it did, S-Tek said 90% likely the servo failed and took out the on board fuse in the controller and maybe a transistor or two. APC tested the servo and sure enough... once I got it in their shop the manager said no worries we’ll pull the servo order the part, pull the head and test it and repair hear and if they have the servo in Texas we’ll have you out the door Thursday or Friday.
    Plus you’ll be $2000 lighter.


    Sent from my iPhone using Tapatalk

  25. #25
    Eddie Foy's Avatar
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    That should correct the left lean caused by his wallet now!


    Quote Originally Posted by SteveE View Post
    Plus you’ll be $2000 lighter.


    Sent from my iPhone using Tapatalk
    "Put out my hand and touched the face of God!"

  26. #26
    wireweinie's Avatar
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    Lighter means he can load more fuel/cargo!

    Web
    Life's tough . . . wear a cup.

  27. #27
    SteveE's Avatar
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    Quote Originally Posted by wireweinie View Post
    Lighter means he can load more fuel/cargo!

    Web
    But you have to have funds first.


    Sent from my iPhone using Tapatalk
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  28. #28

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    Quote Originally Posted by SteveE View Post
    Plus you’ll be $2000 lighter.


    Sent from my iPhone using Tapatalk
    Your turns coming, how's the helicopter shopping coming along?
    Last edited by OLDCROWE; 01-31-2019 at 03:09 PM.
    Remember, These are the Good old Days!

  29. #29

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    Update: Test flight yesterday in very blustery conditions with their test pilot in the right seat. Got level and trimmed then Ralph made a few tweaks on the controller and presto 36K was holding course steadily upwind, downwind and cross wind. Final verdict was a new roll servo (had to drill out and re-rivet the inspection ring thingie to get the roll servo out and back in) plus they gave the horizontal servo a good cleaning and flossing and rebuild of the control head for a grand total of $3450. Now it’s back to that airplane earring it’s keep!
    Remember, These are the Good old Days!
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