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Non-Working Kingmax Sailwinch Wanted


John949
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Trying to repair a friend's sailwinch and the feedback pot has gone open circuit and it appears to be a custom part.  Has anybody got a non-working Kingmax (or Turnigy) servo that they would let go for a nominal sum?  The servo I'm trying to fix is an SW6114MD but the pot appears to be common to all their sailwinches.

I know they don't cost much but it seems a shame to chuck it away for such a simple fault.

Thanks

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John

I have found the KingMax SW6114MD which burnt out in my Marblehead. The output shaft is seized (suspect motor) and it is missing its cable. Not a clue to what else may be wrong.

If you think it may be able to supply any spares you are welcome to it.  Let me know if you want it and I will try to find some packaging and put it in the post. It will be after the weekend before I can send.

You can P.M. me your address or phone number and I will call you to get details.

Eric

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John

Dropped off winch at Post Office this morning. Hope it can supply the part you want (never bothered to open it up just replaced and put it in the box of junked parts)

Hope this enables you to get you friends winch working, and returned to him. Please keep us informed of progress.

Eric

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Eric (and anyone else who is interested), here's what I found when I took your winch apart.  

First picture is a comparison of the two winches. Left is one a club member gave me (just stopped working), right is Eric''s (suspected burn out)

20220516_093521.thumb.jpg.5d216c6619b7bec98171d3f1c881695a.jpg

 

No prizes for spotting the problem with Eric's - a clear case of allowing the magic smoke to escape!  The two chips visible are MOSFETs - basically electronic switches that control the motor current.  The sharp eyed may notice that the circuit boards are slightly different - extra capacitors on the left hand one.  Don't know which is the newer model.  Digging a little deeper showed that Eric's motor had seized and was also open circuit (I was expecting it to be short circuit).  Can't be sure of the exact sequence of events but I think the motor overheated first and melted the commutator, which then shorted and took out the FET.  The commutator then melted further and went open circuit.

I think this shows that the motor cannot take the full stall current for long - rather poor design but definitely worth knowing.

Here is a picture of what's inside a coreless motor.  Apparently the wire cage rotates and the central magnet stays still.  I was expecting the windings to be melted but they look fine.  The commutator was however a melted mess.

20220516_102007.thumb.jpg.f649ee92e3af5b6d0a33e87317ce0226.jpg

 

Sorry Eric but when the FET went phut it damaged the PCB quite badly so I used your potentiometer to repair Keith's.  It even seems to be working!

There are still a few bits that are OK e.g. the case and the geartrain, so if anyone needs them let me know.  I also took some pictures and can provide guidance on how to take it apart and put it back together (you need to de-solder the pot)

 

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John

First off mega impressed by Royal Mail as only sent winch at lunch time Saturday 2nd Class!

As you surmised I believe that the motor overheated first as I had badly set up winch on radio end points with the knot on sheet too close to the through deck fitting. This meant if I left the boat fully sheeted in the winch was still trying to pull the sheets further than the knot allowed hence the over heat. (entirely my fault) The winch was a very early incarnation of the KingMax (Probably 2015 fitted to a swing rig Marblehead).  It's replacement still working! (Fingers Crossed and Wood touched)

Glad it was not a total loss sending you the winch as at least you have got your friends winch functioning. Hope it gives him hours of sailing pleasure. Pleased now I had not opened the case as it would have ended up in the dustbin as scrap rather than a parts provider.

Thanks for the education on servo build could do with having you local to provide advice. (may end up contacting you if I have problems in the future if you don't mind)

Eric

 

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Yes well done Royal Mail, it arrived first thing this morning.  By all means contact me.  If I can help I will.  Same goes for anyone else.  If you want to send me non-working kit, I'll take a look.  No promises, no guarantees, but no charge either.  If I fix it and you are happy then make a donation to your favourite charity.

Forgot to mention that these servos are definitely not waterproof.  Keith's showed some water deposits, so don't leave your boat sealed up between outings.

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