RoboSavvy Forum

HSR-8498 lock up

2012-05-27T23:25:53+01:00

Another update: After cleaning the grease residue from the casing in the hole where the gear axle sits I put the servo back together with clean gears that I sprayed the CRC brand white lithium aerosol on. When turning the MRC3000 on and testing the servo with the servo manager it responded almost perfectly, the only problem was with changing direction at the slowest speed but that was within normal parameters. So now I will do the same with the other servos and hopefully get some play out of my Nova while waiting to accumulate funds for fresh servos. I hope anyone who reads this topic will find the information to be helpful for keeping your Nova's alive longer.

Statistics: Posted by serithseraki — Sun May 27, 2012 11:25 pm

HSR-8498 lock up

2012-05-27T17:36:42+01:00

Thank you, that was far more information than expected, and this has helped me in considering the Dynamixel line for future projects. After testing the contact cleaner the CRC brand is good quality and it didn't damage my working potentiometer but made no difference on the possibly damaged one so I will rule that out as my problem. I believe the first gear is not meshing properly with the brass gear and I found some grease in the hole for where the axle sits "no idea how it got there" but after some thorough cleaning I may work. Regardless, it seems as though I am saving up for a mass servo purchase.

Statistics: Posted by serithseraki — Sun May 27, 2012 5:36 pm

HSR-8498 lock up

2012-05-27T15:49:51+01:00

It's always good to test a spray on the plastic. Some soft plastics can be problematic. I can check the potentiometer in the burned out servo I have and see if there's an easy and non-destructive way to pull the shell off.

Regarding the lithium grease - I'd say NO to that stuff for ANYTHING in a servo! What I've seen is thick and very sticky, and not good for things that have to spin fast. I use some on my metal working machines, but only for slow moving purposes (manually rotated bits, etc).

I use the Hitec-branded servo grease in my servos (it's thin, but won't run away like oil). Be sure to use only as much grease as is needed - too much is as bad or worse than not enough. When you say the motor is tight, do you mean when you rotate the brass gear? You should feel the magnets when you turn the shaft, but the motor shouldn't be "tight" (but then, as I recall, there is no easy way to turn the shaft).

These motors are sealed, meaning they can't be easily lubricated properly. They're not even intended to be lubricated! But, as something to try, you would:

* Remove any grease on the gear end of the motor.
* Apply a drop to the bushing /axle area.
* Power it on without the adjacent gear and listen for the RPM to increase, meaning the oil is working in (no more than a matter of seconds should be necessary).
* Power down, clean excess, repeat a few times.

One thing to note about these motors - they have a fixed lifetime because they are sealed brushed motors. Once the brushes wear out, the motor is done. It would be nice if servos used motors with replaceable brushes, or better yet brushless motors, but it seems the majority use sealed brushed motors. In the case of Hitec, it's more frustrating because of how the motor is mounted to the casing - if you could find a replacement motor, getting the old one out is still a problem.

Statistics: Posted by PaulL — Sun May 27, 2012 3:49 pm

HSR-8498 lock up

2012-05-24T18:20:30+01:00

I ended up getting the CRC brand contact cleaner from a local hardware store. Although I still need to test it to make sure it doesn't dissolve plastic. But from my research I have seen people take the potentiometer apart and clean the contacts directly. Is there a way to disassemble the plastic case without destroying it or will spraying into the gap suffice? Furthermore, as a unrelated question, is white lithium the preferred grease for the brass gear on the servo motor? I ask as the motor seems to be tight and I read brushing oil on the motor shaft could fix this, but how would I do this?

Statistics: Posted by serithseraki — Thu May 24, 2012 6:20 pm

HSR-8498 lock up

2012-05-24T10:54:36+01:00

I can't say there's one I'd recommend, but I haven't had issues with any I've had around up over the years. I usually just go with whatever I can find at Radio Shack.

The sprays dissipate pretty quickly - shake out the excess, and wait 5 or 10 minutes (use a fan to dry it faster). On a surface, they dissipate VERY quickly.

I can't stress enough, you MUST use a spray intended for electronics repair. Don't use acetone or WD-40 or anything like those.

Statistics: Posted by PaulL — Thu May 24, 2012 10:54 am

HSR-8498 lock up

2012-05-20T18:25:39+01:00

Is there a particular brand of "contact cleaner" that you recommend, or will any with a tube nozzle work fine? Also, do I have to let the unit dry for a set period after spraying?

Statistics: Posted by serithseraki — Sun May 20, 2012 6:25 pm

HSR-8498 lock up

2012-05-19T15:42:48+01:00

Krud tends to build up in potentiometers over time / usage. If they're not fully sealed, you can clean them with electronics-safe sprays (they're referred to as "contact cleaner", "potentiometer clearn", and such). You basically saturate the pot using a small tube on your can of spray, getting the spray into the case of the potentiometer, and letting the spray run out. It's best to manually rotate the potentiometer while spraying. DO NOT do this with power applied. In the case of these Hitec servos, you'll need to get to the pot, meaning the board has to come out.

Statistics: Posted by PaulL — Sat May 19, 2012 3:42 pm

HSR-8498 lock up

2012-05-18T05:44:14+01:00

Would this be due to wear on the potentiometer from having it hold particular positions? I read elsewhere that the potentiometer could be cleaned, does someone know the means to do this and can explain it to me?

Statistics: Posted by serithseraki — Fri May 18, 2012 5:44 am

HSR-8498 lock up

2012-05-08T01:13:53+01:00

I had cleaned the case to the best of my efforts. I use a paper towel, antimicrobial cloth and a dental tree "the small pipe cleaner kind". I believe the white lithium grease I placed on the new gears was poor quality as it congealed and led to problems.

Statistics: Posted by serithseraki — Tue May 08, 2012 1:13 am

HSR-8498 lock up

2012-05-07T22:22:56+01:00

If you replaced the gears due to a broken gear it is essential to remove all the existing grease in case it has broken teeth in it. I have replaced gears in the past and then had instant failure of new gears by failing to do this.

I don't know what is good solvent because the material of all the servo components is unknown. I use a lint free cotton cloth and a small paintbrush without solvent. Inspect with a magnifying glass for debris.

I then regrease with Futaba servo gear grease.

Statistics: Posted by i-Bot — Mon May 07, 2012 10:22 pm

HSR-8498 lock up

2012-05-07T16:34:44+01:00

Time for a slight update. After disassembling a servo and cleaning as much of the grease that was possible, I ran the servo and there was an improvement in its motion. This led me to believe the grease congealed and gummed up the servo. So after doing research I found that automotive stores have a more viscous spray version of the grease and my question to the forum is does anyone have experience with this type of grease? Furthermore, is there a specific cleaning solution that can dissolve the grease fully without damaging the gear?

Statistics: Posted by serithseraki — Mon May 07, 2012 4:34 pm

HSR-8498 lock up

2012-05-04T23:30:38+01:00

I have tested a single servo on the board and again with its symmetrical counterpart working in unison. The problem is not consistent between multiple servos, but random and leads me to believe the new gears may be imperfect.

Statistics: Posted by serithseraki — Fri May 04, 2012 11:30 pm

HSR-8498 lock up

2012-05-04T18:38:02+01:00

When you have this problem, how many servo are connect to MR-C3024 ?
Try only one Servo at a time!

Statistics: Posted by ostro_goto — Fri May 04, 2012 6:38 pm

HSR-8498 lock up

2012-05-04T18:15:05+01:00

If I had the funds to afford such things I would, but sadly I can only afford minor fixes. I think it could be two things. One, the case needs replacing or two, the potentiometer needs cleaning. On most of the servos the problem ranges seem to mostly be between 54-56, 94-104, and 160-168 degrees. Has anyone else in the forum had servo lock up and found a fix for it? My current plan is to buy more lubricant and clean the gears to see if there is any grit present, then rearrange the gears and hope it works.

Statistics: Posted by serithseraki — Fri May 04, 2012 6:15 pm

HSR-8498 lock up

2012-05-04T18:43:23+01:00

I have two solutions!
1) Try a 15A UBEC, and lipo batteries! if not work, solution two !
2) buy another brand of servo

Statistics: Posted by ostro_goto — Fri May 04, 2012 12:36 pm