Beware of this servo!!!

by RTECH Thu 27 Feb 2014 - 17:53

Guys , beware of this servo from rcmart. I order 2 of them both damaged.
1st one I use only as few times, servo start to glitch and run out of centre.
2nd servo glitch like hell the moment I plug into my receiver.

I have tested using different receiver and transmitter also the same problem.
I have tested the servo with servo tester and it very unstable.

Crying or Very sad

by laneboysrc Thu 27 Feb 2014 - 19:03

Thanks for the info. For even less I can recommend the Feetech FT5478M. Similar specs, also low profile. Available at RC Mart too.

Have you opened them up to check how they are built? Maybe a wire came loose; in the cheap servos the PCB usually just hangs on the wires.

by RTECH Thu 27 Feb 2014 - 20:11

laneboysrc wrote:Thanks for the info. For even less I can recommend the Feetech FT5478M. Similar specs, also low profile. Available at RC Mart too.

Have you opened them up to check how they are built? Maybe a wire came loose; in the cheap servos the PCB usually just hangs on the wires.

Yeah , I have place another order for the FT5478M.

I have open the two faulty servo. Seems identical to me. Maybe the glitching and neutral problem cause by the faulty potentiometer.

[img] Beware of this servo!!! Grq4_b17_u8vkf

Uploaded at ImageFra.me[/img]

by laneboysrc Thu 27 Feb 2014 - 21:39

Thanks for the hi-res photo, very interesting geek

Looks actually quite good. The PCB is directly soldered onto the motor, so it is stable. Also the potentiometer seems to be directly connected to the PCB, no wires that potentially break like in other cheap servos (including Feetech).

It seems they have skimped on bypass capacitors though. On the left side near the bottom are 4 large solder pads where I believe would normally go two tantalum capacitors for power supply filtering. Those are "expensive" and they seem to be missing. Beside the potentiometer -- as you right fully hinted -- that could also be the source of a problem.

by dragonl Thu 27 Feb 2014 - 22:08

With both PCB side by side, it looks like it is solder manually or its has been twitched. The one on the right, the PCB look scored to me.

by RTECH Sun 2 Mar 2014 - 10:41

Ok , new findings... This servo only perform best with certain brand of radio system.
Maybe due to the types of transmitting frequency. All the radios shown below does not cross bind each other at all.

The hobbyking radio, servo glitch . Will cause the throttle glitch also. Sudden car move
forward when servo is turn at fast pace. Nothing wrong with the radio when using other servo.
Beware of this servo!!! 44693

Sanwa MX-V , servo glitch like hell , run off neutral.
Beware of this servo!!! Mx-v

Perfect !

Beware of this servo!!! Radiocomanda-digitala-etronix-pulse-ex3gpro-3-canale-cu-stick~2259233

by laneboysrc Sun 2 Mar 2014 - 21:13

That's weird. If the car runs off when you move the servo then that could be that the BEC is not strong enough, and the high current draw of the digital servo is causing the voltage to sag, causing havoc in the receiver.
The etronix seems to be the same hardware as the HobbyKing HK300/301/X-3S radios.

by RTECH Mon 3 Mar 2014 - 17:58

laneboysrc wrote:That's weird. If the car runs off when you move the servo then that could be that the BEC is not strong enough, and the high current draw of the digital servo is causing the voltage to sag, causing havoc in the receiver.
The etronix seems to be the same hardware as the HobbyKing HK300/301/X-3S radios.

Yea, suspect this digital servo draw a lot of current, creating power surge.
Maybe the etronix same circuit design as HK but using better component??

I remember last time I use the high torque digital servo for my wraith crawler also have the servo glitching issue. I solve the problem by routing the servo power directly from the lipo battery. The servo is a high voltage servo.

This time round I can't do the same as this servo max. voltage is 6v. Maybe I have to get a external high current BEC for the servo supply.

by gexer Wed 13 Apr 2016 - 23:04

Actually I love this servo. I use it on all my rides. Lol

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