Hitec Servo Issue

[Xraycer]

Today, I decided to upgrade my Redcat Gen8V2 stock Hexfly servo to a old Hitec hs7950th. I've had this on my Axial ZR10 comp crawler for the past 10 years. This was the servo of choice for comp crawlers back then.
I'd set up endpoints with my Skyfly transmitter, and the first test run, everything went fine. After about 5 minutes of use, the steering went fully left and wouldn't turn back right at all.
So, I removed the servo horn, turn the power back on to let the servo reset to neutral, and remounted the servo horn. I tested it while the rig was on the stand. Now, every time I turned it left, it would reset slightly left of the neutral position. It would keep resetting back further and further left until the wheels maxed out to the left. I again repeated the same mounting and remounting procedure, but it still did the same thing.
Any ideas what's going on?

@Greywolf74 @WickedFog

 

[WickedFog]

Sounds to me like something has come loose in the servo. It should be rebuildable, so you should be able to pull it apart and see if there is anything wrong inside.

That is a programmable servo. Do you have a programmer for it?
https://www.towerhobbies.com/produc...kxi6nDVBWdu5HFE9GSBnk9JTdOe8c93RoCx80QAvD_BwE

Try this...
Do the whole turn left thing until it gets pretty far out of position. Then manually turn the horn back to the right, kinda forcefully, but with the power off. When you power the receiver back on, does it return back closer to where center originally was? If so, something is probably moving freely inside the servo that should be fixed.

 

[Greywolf74]

Do you have a stand alone servo tester?

 

[WickedFog]

Do you have a stand alone servo tester?

That's a good idea. Take the radio out of the mix
Also, the potentiometer came loose in my old Futaba Jr years ago. When I was driving it, it all of a sudden started turning one direction. When I corrected it, it steered in that direction. It took me a minute to figure that one out. When I took the TX apart, there was a plastic tab that held the potentiometer from turning that had broken off from all the use when the nut that held the potentiometer in came loose. Likely, not your issue @Xraycer, but if all other diagnosis fail...

 

[STONER RC]

Today, I decided to upgrade my Redcat Gen8V2 stock Hexfly servo to a old Hitec hs7950th. I've had this on my Axial ZR10 comp crawler for the past 10 years. This was the servo of choice for comp crawlers back then.
I'd set up endpoints with my Skyfly transmitter, and the first test run, everything went fine. After about 5 minutes of use, the steering went fully left and wouldn't turn back right at all.
So, I removed the servo horn, turn the power back on to let the servo reset to neutral, and remounted the servo horn. I tested it while the rig was on the stand. Now, every time I turned it left, it would reset slightly left of the neutral position. It would keep resetting back further and further left until the wheels maxed out to the left. I again repeated the same mounting and remounting procedure, but it still did the same thing.
Any ideas what's going on?

@Greywolf74 @WickedFog

Before you installed the servo did you do a test run on it? Make sure it was working properly? 10 yrs old correct. Might be time for rebuild for it or a new servo all together. Does it have a servo saver on it? Is all the steering linkage smooth not getting hung up? Could be the saver..the trim is set 0° as well. Do you use the little rubber grommets that the servos come with? Those are for reducing the vibrations to the servo.. might be a idea for next time when in stalling servo if you don't all ready...honestly sounds like it's just worn-out and needs a rebuild or just replace with a newer one. They are good cheaper ones on ebay or Amazon. As you probably already know... take it out run it threw some tests.. do you have another TX and RX to connect it to? Might be the the TX like WICKED SAID...

 

[Xraycer]

Try this...
Do the whole turn left thing until it gets pretty far out of position. Then manually turn the horn back to the right, kinda forcefully, but with the power off. When you power the receiver back on, does it return back closer to where center originally was? If so, something is probably moving freely inside the servo that should be fixed.

No, it recenenters to the left. Then the recentering goes further left every time I steer it left and let go of the steering wheel.

This is at least a 10yo servo. I don't recall anything about it being able to be programmed. Not sure if that was even a thing back then.

Before you installed the servo did you do a test run on it? Make sure it was working properly? 10 yrs old correct. Might be time for rebuild for it or a new servo all together. Does it have a servo saver on it? Is all the steering linkage smooth not getting hung up? Could be the saver..the trim is set 0° as well. Do you use the little rubber grommets that the servos come with? Those are for reducing the vibrations to the servo.. might be a idea for next time when in stalling servo if you don't all ready...honestly sounds like it's just worn-out and needs a rebuild or just replace with a newer one. They are good cheaper ones on ebay or Amazon. As you probably already know... take it out run it threw some tests.. do you have another TX and RX to connect it to? Might be the the TX like WICKED SAID...

It ran fine initially for about 5 minutes. Steering linkage is smooth as butter. This is a crawler so no servo saver.

 

[WickedFog]

This is at least a 10yo servo. I don't recall anything about it being able to be programmed. Not sure if that was even a thing back then.

This was a thing back then. Not sure when they actually came out, but I know I had a programmable servo around 10 years ago. I don't remember which one it was, but I never had a programmer for it. It came on a car I bought.

Is this your servo?

 

[Xraycer]

Yep

 

[WickedFog]

Have you tried it on another receiver? It should be programmable. If they changed that feature over the years, they would have changed the model number I would think.

It was reviewed by Chubby at Big Squid over 10 years ago, and it was a very good servo then...
https://www.bigsquidrc.com/hitec-hs-7950th-review/

 

[STONER RC]

Have you tried it on another receiver? It should be programmable. If they changed that feature over the years, they would have changed the model number I would think.

It was reviewed by Chubby at Big Squid over 10 years ago, and it was a very good servo then...
https://www.bigsquidrc.com/hitec-hs-7950th-review/

Agreed try it with another controller and receiver. See what it does.. have you actually tried that yet sir??

, it recenenters to the left. Then the recentering goes further left every time I steer

Have you looked in it yet?? Maybe it needs to be shifted over a little bit.

 

[Greywolf74]

I think thats the same exact servo I have in my old OFNA MBX 9.5. Solid servo. overall I mean

 

[WickedFog]

I think thats the same exact servo I have in my old OFNA MBX 9.5. Solid servo. overall I mean

It got a killer review at Big Squid. But then again, all the Hitec line are pretty darn good.

 

[Xraycer]

Like I said, it was the servo of choice for crawlers back then.

I'm going to put the stock servo back on, and try to figure out this Hitec servo issue another day.

Thanks for the input, guys!

 

[STONER RC]

Like I said, it was the servo of choice for crawlers back then.

I'm going to put the stock servo back on, and try to figure out this Hitec servo issue another day.

Thanks for the input, guys!

Like you said bud "back then" 10 yrs ago... it was solid for sure. But it's been used for 10 yrs.. just worn out that's all. Can you get new gears for it??

 

[Xraycer]

Like you said bud "back then" 10 yrs ago... it was solid for sure. But it's been used for 10 yrs.. just worn out that's all. Can you get new gears for it??

It was actually not used that much. The Axial ZR10 was a kit I had built, and the gears never ran smooth. Then I got a Wraith, and that became my main ride. So, that servo had hardly any usage time.
About a year later, I lost interest in the rc hobby..............until this year.......10 years later.