Esc/ servo issue

[TownsendTdi]

Shortly after getting my trail trekker (a month or so) it started having a steering issue- when turning it on sometimes I would only have throttle response, zero steering, not even the twitch when turning on. I'd have to cycle the on/off switch multiple times then it would work. This was not every time but still very frustrating. It happened with a different tx as well. Horizon hobby sent me a new ESC. That process took a week or so and I was still using the truck in the meantime. Last week my steering stopped mid-run, the servo felt pretty warm and I assumed the servo had died. I ordered a hs-65mg. I first plugged it into the servo I had been using (with the slight issue) and not even a twitch. I then plugged a brand new (plugged it in once in my micro d.t. and it worked) sm-22 into the original esc to troubleshoot and no response either. I then tried the new esc, not a twitch from either. I tied plugging them both into my micro d.t. and micro sct and no response. I can plug a light set from the night crawler into all 4 of these esc's and they work fine. I cannot try the stock servo (I opened it up thinking it was garbage and dropped a tiny gear).
Not knowing a ton about these electronics here's my theory: did that original esc fry the original servo, then the 2 brand new ones? Is that possible? Would the led lights work ok like they do if that was the case?
Any ideas?
Thanks! Please help Im going nuts without my truck!

[TownsendTdi]

And who the hell decided not to include u-joints with the trekker driveshafts?
And the stock 5-wire servo in the sct died today too. Man, no luck with the micros today! Looks like I need to stock up on servos...

[DANALLY]

Man what a story!!! I've had a few like that with these rigs. It's always been the esc. I've had some that lit up and caught fire for no reason. Others take any motor you throw at them and never heat up.

The servo situation is strange though. Did you play with the servo moving it back and forth before you had it powered up!?! I have ruined a few micro servos that way. My son kept turning it by hand with the power off and the servo died because of it. Just a thought.

[TownsendTdi]

I didn't try to move the servos manually before, just after they appear dead (wanted to confirm that they could move).
The other micros work fine with the 5-wire servos, and I can plug that light set into them all through the 3 wire plug and have it light up. So i think those esc's are ok and i can only point my finger at the servos (or myself for trying all of them on a possibly faulty esc!)
I know the sm-22 worked when I got it. I plugged it in to check but didn't install. The hs-65mg could have been a dud I suppose, but it seems highly unlikely that the sm-22 would just stop working too- it was put back into bubble wrap and has been in it's box since.
I have used dielectric grease on some 1:1 car electrical connections with great results (MAF sensor plug, corroded bulbs and stuff...) would it hurt anything to put a dab on the plug?

Jim mentioned something about a BEC regulating current going to the servo at 5w, I checked the left two wires for the servo with the 2S lipo plugged in and it read around 4.6 on the "faulty" esc. Don't know if that means anything, but i figured if there was too much power going to them or something like, they could take a dump.

[Fungi]

The LED lights will only indicate if enough voltage is there to illuminate them, and is not accurate enough to indicate if there is enough voltage for a servo to operate properly. The esc generates pulses the servo uses to know where to position the output shaft. If the pulses are missing it could indicate there is a problem with the esc. This is easy to test with an oscilliscope. An estimation of the pulses being present can be made with a volt meter by measuring the voltage across the ground and the pulse line in vdc, but the value will be very small (250mv to 500mv). The measured value should change when turning the steering wheel, where it is higher in one direction and lower in the other.

The correct voltage on the servo power pins depends on the battery you are using. If it's a lipo the voltage should always be 5vdc at the servo. If you're using the NiMH then the 4.6vdc could be correct. If the NiMH is fully charged it should read 6vdc and the voltage at the servo should be 5vdc. However NiMH will drop to 4.8vdc for the majority of it's discharge cycle and when this happens the 4.6vdc sounds legit. However if you are measuring 4.6vdc with a Lipo, that is bad and the esc voltage regulator is damaged, or the servo is drawing too much current pulling the voltage down.

It is generally not possible for an esc to kill a servo. An esc can theoretically send the wrong value of pulses to the servo causing it to rotate beyond a mechanical stop and break gears, but that's not fitting the story. The esc can provide less voltage than the servo requires if it's voltage regulator is damaged, but this will not damage a servo.

If the servo is damaged mechanically or electrically and it is drawing more current from the esc than the voltage regulator can provide the microcontroller on the esc can brown out and not function properly, but this would also prevent it binding and from controlling the main motor as well.

While I'm at it, the servo connection is polarized and the servo will only work if plugged in correctly. It will not be damaged by plugging it in backwards, but it will not function.

[TownsendTdi]

Ummm...mystery solved. Plugged in wrong.
There aren't many guides about taking these machines apart except for the exploded view, so someone like myself who is new to rc's takes special care, notes, even pictures before I disassemble something (for the first time at least). I was so sure that plug was the other way! And not knowing that it wouldn't screw something up, I didn't try to flip it. Thanks for the responses- I wouldn't have tried (maybe eventually) flipping that plug if you didn't tell me it wouldn't harm anything.
I'm off to cram that hs-65 in my truck with a smile on my face, ego feels a little silly though. Thanks again!

[Fungi]

I won the internet today! drops mic, walks away... lol

[Ghost]

A general rule of thumb is most rc rx's have the ground wire closest to the outside edge of the unit when pluging in esc's servos ect