michaelbbbb

I have recently had two different HS 75BB retract servos fail in a yet to be flown 60 size warbird (TF P-51).
I am using a voltage regulator, and the receiver/servos all get 5.4V.

In both cases, I"m only getting a few cycles up and down for the main retracts. At some point, the servo stops reacting at all, and further testing with a replacement shows that it is indeed a bad servo. This model calls for one retract servo only, and there doesn't seem to be anything binding.....
Any suggestions on why I'm unable to keep this servo healthy?
Do I need to use dual servos for this applicaion.?

A.T.

Have not seen a faulty HS-75BB to date. The servo must be free to rotate the full 180 degrees, and the servo retracts both correctly lock into the up or down position. If for any reason the servo does not retract or extend fully to let the servo reach full movement in both directions, any retract servo will fail.
Hitec HS-75BB Retract Servo Specification
Information available under "Retract Undercarriage, Flaps and payload release" at
Alan's Hobby, Model & RC FAQ Web Links may assist.
Regards
Alan T.

crazy8s

My Feedback: (21)

I've been using the HS-75BB retract servos for a couple of years now, currently have 3 operational in H9 warbirds, and they are fine except the one that I was about to install in a new plane last week. It failed straight out of the box. I hooked it up to a receiver before installing it in the plane so obviously it was under NO strain and I discovered that it would only travel in 1 direction. It would not return 180 degrees in the other direction when the switch was flipped. To eliminate it being a transmitter or receiver problem I used a different transmitter and receiver and had the same result. My LHS replaced it with a good unit after I gave them the demo. I hope we don't find out that for costs sake the manufacturer is using cheaper and poorly manufactured electronics in these servos.

MikeMayberry

My Feedback: (1)

As with any electronic device, there can be failures from time to time. The components have not changed in this servo.

Mike.

1UGLYPUG

HI FOLKS. I HAVE HAD 3 FAILURES OF THE 75BB RETRACT SERVO, CAUSING DAMAGE TO MY NEW HANGER 9 60 SIZE SPITFIRE. I HAVE BEEN LUCKY ENOUGH TO HAVE A GREAT HOBBY SHOP THAT REPLACED EACH ONE, UNTIL I FINALLY BOUGHT A JR SERVO. I BELIEVE I HAVE FOUND THE PROBLEM WITH THE SERVO, SHORTING, OR BURNIN OUT. THE HOBBY SHOP GUY TRIED TO INSIST THAT I MUST HAVE HAD THE SERVO BINDING, BUT I INSTALLED THE ONE IN MY 60 SIZE HANGER 9 CORSAIR, AND HAVE HAD NO PROBLEMS. THE SECOND SERVO THAT WENT BAD, I HAD NOT EVEN INSTALLED IN THE PLANE. I HAD THE SERVO POWERED, AND WAS SQUEEZING THE RETRACT ARM ONTO THE SERVO, AND IT WOULD "JUMP" OR WIGGLE WHEN I TRIED TO SQUEEZE THE ARM ON. I TOOK IT BACK AND SHOWED THE HOBBY SHOP, AND THEY AGREED IT WAS BAD,,,,, NOW,,, ON TO THE THIRD SERVO. I WAS FLYING, AND BEFORE I GOT READY, THE GEAR STARTED TO DROP HALF WAY DOWN, JUST LIKE THE FIRST TIME. I LANDED GEAR HALF UP/DOWN, CAUSING MORE DAMAGE TO MY PLANE. I TOOK IT TO THE HOBBY SHOP AGAIN, AND SHOWED THE GUY THAT IT WAS NOT BINDING,, AND INSISTED HE OPEN IT UP SO WE COULD LOOK INSIDE. HERE IS WHAT I SAW. ON THE BOTTOM OF THE SERVO,, THE WIRES TRAVEL ALONG THE BOTTOM OF THE SERVO CASING, ALONG THE BOTTOM OF A LITTLE CIRCUIT BOARD,,,,,,,,,,, AND LO AND BEHOLD, THERE IS SOME SHARP PINS STICKING DOWNWARD, RIGHT INTO THE WIRES !!!
AFTER SOME FLYING, THE VIBRATION OF THE ENGINE, WILL CAUSE THE WIRE TO BE WORN UNTIL IT SHORTS !!! THAT IS WHY WHEN I WAS PRESSING DOWN ON THE SERVO TO INSTALL THE ARM, IT JIGGLED OR WIGGLED,,,, I HAVE AN OLDER 75BB RETRACT THAT IS NOT MADE THIS WAY. IT SEEMS ONLY SOME OF THEM, OR MAYBE THE NEWER ONES ARE MADE THIS WAY. IT HAD A LITTLE RED STICKER ON IT WITH 03 08 OR 08 03 ON IT.... USE THESE SERVOS AT YOUR OWN PERIL ,,, I WILL NEVER USE ANOTHER ONE UNTIL I AM SURE THEY HAVE CORRECTED THIS..... YOU MAY TRY SQUEEZING THEM WITH POWER ON TO SEE IF IT SHORTS,,, OR OPEN IT UP AND SEE IF THE WIRES ARE UP AGAINST THE BOTTOM OF A CIRCUIT BOARD WITH LITTLE PINS STICKING DOWN THAT CAN PENETRATE THE WIRES,,,, ACCIDENT WAITING TO HAPPEN,,, DAY,,,,

tiger650

My Feedback: (22)

I am now having the same exact problem with my Hitec HS 75 BB retract servo. I have had 2 fail within 3 cycles of the gear. How did you resolve the problem with yours?
thanks,
Bob

1UGLYPUG

IF YOU OPEN UP ONE OF THESE SERVOS,, A NEW ONE, AS THE OLD ONES ARE ASSEMBLED DIFFERENTLY INSIDE,,, YOU WILL SEE THAT THE WIRES RUN IN THE BOTTOM OF THE SERVO CASE,, AND THE COMPONENT BOARDS , WITH THE SHARP ENDS OF THE SOLDERED COMPONENTS, POINT DOWN INTO THE BOTTOM OF THE CASE,AND WILL EVENTUALLY PUNCTURE THE WIRES,, SHORTING OUT THE SERVO. I HAD 3 OF THESE STUPID THINGS SHORT OUT,, TWO IN FLIGHT, AND RESULTED IN THE SERVOS EXTENDING THE GEAR IN FLIGHT,,, AND ONLY PART WAY,,, RESULTING IN A DAMAGED AIRCRAFT. I BOUGHT A JR SERVO AND HAVE HAD NO MORE PROBLEMS. I WILL NEVER USE A HITEC SERVO AGAIN, UNTIL THEY START ASSEMBLING THESE THINGS SO THE WIRES WON'T SHORT OUT ON THE COMPONENTS,,, USE AT YOUR OWN RISK,,, DAY

freeair

i have noticed this problem with Hitec servos , yes the soldered ends of the PC board protude down to a tiny space to where the servo wires run out. if you remove the servo case bottom and don,t place the wires back correctly in the tiny space provided your sure to get a short circut in one of the 3 wires. take your pic; positive / negative / signal.

1UGLYPUG

MINE CAME THAT WAY,, ARE YOU SAYING WE NEED TO OPEN THEM ALL UP AND FIX THE WIRES BEFORE WE USE THEM?? IF SO, THE COMPANY NEEDS TO FIX IT BEFORE I WILL BUY ANYMORE. I DON'T CARE IF YOU " PLACE THEM CORRECTLY OR NOT, THE WIRES SHOULD NOT BE PLACED UNDER A CIRCUIT BOARD THAT HAS SHARP ENDS OF COMPONENTS IN SUCH A POSITION THEY CAN STICK INTO THEM. POOR DESIGN AND/OR ASSEMBLY. BUY A JR,,, IT WORKS RIGHT THE FIRST AND EVERY TIME...... DAY,,,

pc55bomber

Hi Mike

I have heaps of Hitec servo's and luv em, but I have just had 2 x HS75BB retract servo's fail yesterday at the field, simply stopped working from the time I assembled the aircraft, put the gear down, all OK and that was it no responce at all from either of them.
Checked it out at home and both servo's are dead, no heat ,no smoke, nothing, and both failing within seconds of each other.
They are fitted to my new Hangar 9 p47 with mechanical gear and have only had a minimum of use (about 8 Flights).

I been flying and building long enough to know what I am doing, they have not been stalled, they lock up and down and operated properly until now.... like 3 days from biggest Scale rally in Australia.[:@]

I have replaced the servo's with 2 new ones but don't want the same to happen to these, and they are working perfect.

There must be something going on here, not just a faulty item as I have heard of more instances then just the above guys.
I am running 5 cell RX packs, could it be the voltage that is causing the problem??
Any input or help would be appreciated as I think there is an issue here.
Thanks
Paul

1UGLYPUG

Open up the bottom of the bad servos,,, see if the bottom of the circuit board has the soldered ends of the components pointing down towards the wires that are under the board and between the bottom of the servo case. The ones I had shorted out when the bottom of the case pushes up against the wires pushing them into the circuit board, and shorting out the servo. I had 3 in a row do that , and I finally got a JR servo. It is a design problem. Mine shorted out in a Hanger 9 Spitfire. It seems the Hanger 9 aircraft don't have much room for the servo and it places pressure on the bottom of the servo,, and with the bad design and assembly of the servo,,, it is just disaster in waiting. The older Hi tec servos are not made this way. I have an older one I opened up and the component board faces up and cannot short into the wires. The new ones may work fine for a while, but will eventually short out. I had one do it in my hand while I was installing it. I had it powered when I was squeezing the servo arm onto the servo, and the servo would jump every time I squeezed it.

1UGLYPUG

Mike,, you do have a problem with these servos. Yes they may have the same components, but they are now assembled differently. I have an older one, and the component board points up away from the wires on the bottom of the servo case. Your new ones have the component board with the wires and component ends on the bottom of the board touching each other and any pressure on the bottom of the servo will eventually short through the insulation, if it is not located in there just right,,,, Until you redesign the assembly of this,, I will be warning all my friends of the problem, and telling them to buy a JR retract servo. You cannot ignore this problem and keep saying they have the same components,,,, People are losing or damaging their expensive airplanes due to you sticking your head in the sand. Have someone look into this problem, and either turn the component board over, or place a thick piece of insulation material between the wires and the component board to stop this from happening. DAY,,,,

pc55bomber

Hi Uglypug

There is no pressure on the servo bottom it hangs in mid air and I have already checked the wiring and cant see any issues there either.
I know quite a few scale glider guys won't use this retract servo as it does exactly what mine have done.

Mike

Any news Mike, I am not griping as I will return the 2 servo's for warranty as my Hitec servo's have never been a problem until this issue.

The 2 new ones I have fitted are working great but how long will they last ????

Your suggestions would be appreciated.

Thanks
Paul

1UGLYPUG

That seems to be a whole new problem. Mine definitely shorted out. I had two short out in flight,, and the gear just dropped half way down and did not lock,, caused damage to the nice new wings of the Spitfire. And the third I found the problem before I installed it. Like I said, I solved my problem with a new JR servo. No more problems. It will be nice to see what Mike finds out about your problem,, I do use some of the Hitec mini servos,, and no electrical problems, although the gears do strip very easily,, had to replace 3 so far,, but, still like the mini 48's ,,, DAY,,,

MikeMayberry

My Feedback: (1)

Since there is no EPA adjustment, it is very important that the linkage be set up so the servo is not trying to move farther than the retract will allow. To maximize the performance you should use the shortest arm (or linkage attachment point) possible while still getting the retract to work properly.

Mike.

pc55bomber

Mike
Have sent you an email
Cheers
Paul

1UGLYPUG

I had no problem with the servo binding or moving too far. The servo shorted out into the wires in the bottom of the servo case. As I said, the JR servo works just fine. It does not go too far, and bind, and burn out the servo, as you seem to be implying. I do know how to install a servo and check that is is not binding. The servo did not move the arm too far. As I said before, one of the servos would jump, when you squeezed the servo while putting on the servo arm, while having power applied through the radio. The servos are assembled in such a way that they will short out. The circuit board has the end of the components pointing down so they can wear into the wires in the bottom of the servo case. As far as I can tell, the servo components are fine, but the assembly is not a good design. I have an older one of the same servos, and it has the component board assembled with the components bottom of the board point up away from the wires and it cannot short into the wires. If only they would look into the assembly of the servo, they could solve this problem and have a perfectly good servo, just like the older ones I have. A good piece of insulation material between the wires and the component board board would also help,,, DA

Howard

My Feedback: (55)

Sir - is your experience that this problem is limited to only the Hitec retract servo or does it also apply to other Hitec servos that you have opened up? Thanks

Howard

My Feedback: (55)

Sir - is your experience that this problem is limited to only the Hitec retract servo or does it also apply to other Hitec servos that you have opened up? Thanks

ADMIN - please delete accidental double post.

1UGLYPUG

HI,, So far it has only been the retract servo. I have not had any problems with the other Hi tec servos, so I have not had to open them up and look at the bottom of the servo. I opened up an older retract servo I had to compare to the new ones that kept shorting out, and it was assembled differently as I said. I use the Hi tec mini 48 servos and have no electrical shorting problem with them. They just seem to strip the gears more easily than other mini servos I use. That must be why the LHS keeps some replacement gears for the Mini 48 servos on stock. They strip easily. But that is another problem, I would not have mentioned, but you asked me if I had problems with any other Hi tec servos. DAY

airmike1271

I too have been using a Hitec HS 75BB retract servo which failed recently. This makes my third retract failure. The first retract that stopped working was a Tower Hobbies (I think) System 2000 TS-63.  The second failed servo is an Expert SL630 and the third is the Hitec HS 75BB.  There is no binding in my applications.  I believe that the first servo failed in flight when using a NiCad 4.8v receiver pack while the later 2 failed in flight powered by NiMHD 6v packs. 

The signal from the receiver checks fine.  These servo failurs have happended after an average of 50 cycles.  Now I am going to shelf the P-51 for a while and fly non retractable landing gear as I am ready for less maintenance and more flight time.  After reading the useful above posts, I conclude that I will fly using JR or Futaba low profile retracts from now on...my 3 cents.

Mike

1UGLYPUG

Hi sir,,,, since I installed the JR servo, I have had no more problems. It is only the Hitec servo that has the wires resting on the componet board is such a way that they can short out onto the servo board. If they would just put some insulation between the wires and the board, or turn the component board over like the old servos of the same type, they could save a lot of heart break on the part of their customers. Until they do, I will stick with JR servos.,,, DAY