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Thread: How to tell.....did I kill a HiTec 7950??

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Old 06-15-2011, 06:13 AM   #1
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Unhappy How to tell.....did I kill a HiTec 7950??

OK, I have a 2.2 Bully rig of ~6.7lbs. It's running 3S, dual CC ESC's, CC 10A BEC (was set to 6.5VDC with the 7955, changed to 7.5VDC for the 7950) wired direct to the servo.
I ran a 7955TG for months with no problem. Did some steering mods (to get more steering) and added the 7950 @ 6.5VDC.
I still needed more steering so went with an Integy long aluminum steering arm (cheap but good for testing, clamping type) and bumped the BEC voltage to 7.5VDC.
Ran maybe a pack through it and had weirdness from the servo. It would randomly stop in a position (turned either way, near neutral, just random). If I let it sit, sometimes it would work again, sometimes I needed to kick a front wheel or move forward/reverse to get steering back.
It did this tires on or off the ground.
At times, I noticed when it stopped, I didn't hear the "hunting/buzz" from the servo. Push the servo arm and it would buzz & work.
I double checked the EPA's, made a minor tweak.
At one point, I checked the servo temp, it was "warm", but not hot.
Figured I fried a CC BEC so put in a new one @ 7.5VDC, same issue.
Swapped steering to another channel to test the RX, same issue.

I did find new servo arm has a deeper pocket in it, this leads to binding. I removed some material from the arm to get some clearance. While there was a bind because of this, you could still "easily" twist the servo arm. With the arm shaved, it's even easier so I don't consider the bind to be real bad.

How do I tell (other than the above) if I fried the servo? Any other ideas?
My son is saying that he has read "many people" have fried 7950's when running @7.5VDC, I don't see that anywhere but maybe I missed it.
I didn't see anything posted that may indicate anything else to check or "issues" with this servo.

Sigh, I picked up another 7950 last night 9comp this weekend) & will deal with HiTec, just want to make sure I don't kill another one.

Yes, long post but wanted it complete to limit replies/questions.
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Old 06-15-2011, 08:14 AM   #2
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From all of the tests you've done it does indeed sound like the servo has kicked the bucket.
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Old 06-15-2011, 09:54 AM   #3
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Mine did same thing and eventually I kept messing with it and it let the magic smoke out. Go ahead and mail it in, it takes about 2 weeks to get it back.
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Old 06-15-2011, 09:58 AM   #4
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Mail it in and since you had to purchase another one to get you by I would ask them to send you back the 7980 just to try out. Can't hurt unless you really like the specs of the 7950 but hey why would you need 2
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Old 06-15-2011, 11:33 AM   #5
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Quote:
Originally Posted by kurtus420 View Post
Mail it in and since you had to purchase another one to get you by I would ask them to send you back the 7980 just to try out. Can't hurt unless you really like the specs of the 7950 but hey why would you need 2
Nice idea, I "may" try that.

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Originally Posted by It usually runs fine View Post
Mine did same thing and eventually I kept messing with it and it let the magic smoke out. Go ahead and mail it in, it takes about 2 weeks to get it back.
Part of why I got another one. I figured I would be waiting for a while.

Quote:
Originally Posted by dmcchaser View Post
From all of the tests you've done it does indeed sound like the servo has kicked the bucket.
Thanks (sorta....) for the verification. Just wanted to make sure I didn't miss something stupid, thus the looong initial post.
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Old 06-17-2011, 07:12 AM   #6
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OK, picked up a new 7950 locally, it went in and everything works (although I dropped the BEC voltage to ~7.2VDC).
Also emailed HiTec to see what they say.

We shall see.
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Old 06-17-2011, 07:59 AM   #7
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You might want to consider getting a hitec hpp-21 programmer, I just bought one for my 7980 and 5955 plus a few buddies run hitecs so it will come in handy in the future. Put that servo into 10% overload protection and according to SCorpionKing it will save that servo from these kinds of issues. Just bought mine for $26 shipped to Canada but seeing how your in the States it may be cheaper yet for you. Check servo city if your interested in it.
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Old 06-17-2011, 09:20 AM   #8
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Quote:
Originally Posted by kurtus420 View Post
You might want to consider getting a hitec hpp-21 programmer, I just bought one for my 7980 and 5955 plus a few buddies run hitecs so it will come in handy in the future. Put that servo into 10% overload protection and according to SCorpionKing it will save that servo from these kinds of issues. Just bought mine for $26 shipped to Canada but seeing how your in the States it may be cheaper yet for you. Check servo city if your interested in it.
I may do that (we have quite a few HiTec's between myself & my son "asw27x".
I have a LHS that is equal/cheaper than ServoCity, they are ~10 miles from home. The 2nd 7950 I bought was $130.00US out the door ($120 + $10 tax), not a bad price.
I believe they are "Power Hobby" in Suffern, NY, but are http://myworld.ebay.com/expresshobby/ online.
I will likely keep this updated.
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Old 06-17-2011, 09:31 AM   #9
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Seems to be on par with rcmart, check them out for super cheap pricing on futaba 4pl(they are updated) and Hitec servos, I was looking at buying the 7980th and was all set to pay the 180 or whatever they go for at horizon, then I jsut found it for $125 + $6 frt and it gets to Canada in 7-10 days marked as a gift. The 7950th is 119 on that site so I say you did just fine bro
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Old 07-13-2011, 06:14 AM   #10
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I know HiTec has had the servo since 6/29 (tracked it via USPS) so it should be back soon.
The new 7950 has been fine.
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Old 07-13-2011, 07:47 AM   #11
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While this thread is up:

What does Hitec require you to send in for warrentee repairs? I.E. The original plastic box, proof of purchase, un-molested wiring? Do you need a warrentee confirmation number before shipping it in?

I ask, because I have a month old 7954SH that jitters and I cut the wiring harness to solder the power and ground straight to the ESC's battery harness and want to know if I should solder it back together like stock before sending it in?

Sorry for the newb question.
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Old 07-13-2011, 08:05 AM   #12
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Hitec wants all the original packaging that you have left box, paperwork etc... Plus a receipt and the form from their website. They want to test the servo to decide if it's a warranty repair or not so I'm guessing it needs the original plug on it.
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Old 07-13-2011, 09:47 PM   #13
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Quote:
Originally Posted by SINister View Post
Hitec wants all the original packaging that you have left box, paperwork etc... Plus a receipt and the form from their website. They want to test the servo to decide if it's a warranty repair or not so I'm guessing it needs the original plug on it.
Hmmmmm....I packed the servo in a bubble bag, dropped it into a small USPS box & shipped it (copies of "proof of purchase" and an email stating to send it back packed inside as well) back to them.
Paperwork has my email address & phone # on it.
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Old 07-15-2011, 02:25 AM   #14
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as long as you fill out and mail in the service request form you can get through their website you should be fine. i have never had an issue for any reason. i dont think i have ever given a reciept for service with a 50 or 80. all servos are covered for 3 years and neither the 50 or 80 have been out that long
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Old 07-18-2011, 08:51 AM   #15
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Default Servo returned to me after service.....

OK, I arrived home from a business trip late Saturday and found my servo had returned (no shipping/tracking info from HiTec....it just "showed up".)

The work sheet stated, "damaged motor, motor replaced". So, maybe I got a bad one, fecal material occurs at times.

My other 7950 is working well at this point. But, I'm still running it within listed voltage limits, not higher.

So, we shall see.

Thanks to HiTec for covering this as it's not a cheap servo.
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Old 09-17-2011, 06:58 AM   #16
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OK, just received our 2 HiTec servos back from the HiTec Doctors...
The 7954 had a "damaged amplifier" and a "damaged motor", the whole servo was replaced.
The 7950 had a "damaged amplifier" and a "damaged motor", both parts were replaced.

Interestingly, the SN's are "next to each other", not sure if it the servo SN or a number assigned to me.

I did get an email when they were received, but not when shipped. Total time was 1.5 weeks.
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Old 09-17-2011, 08:23 AM   #17
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You're luckier than me, I got a repair estimate for $79 to fix my servo I sent in. I opted not to repair it and I bought a CS-170 (rebadged 5955) for $10 more, new gears, new board, new case, etc.

That was four years ago and I'm still using it in my Bully MOA today.
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Old 09-17-2011, 08:34 AM   #18
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I'm curious if the voltage did the damage.
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Old 09-17-2011, 01:06 PM   #19
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Quote:
Originally Posted by EeePee View Post
I'm curious if the voltage did the damage.
I guess you mean the 7.5 volts? The second one in this thread is the one I had repaired from the 1st post. I believe my son was running his CC BEC at max rated voltage, not 7.5 volts. So HiTec got to see the same servo twice in a couple months.
I'm still running my "replacement" I bought.

My son has his 7954 back, so I now have a new 7950 "spare", he was running my "repaired" 7950 until we could ship his 7954 back to HiTec.

Did you follow all that??
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Old 09-17-2011, 01:55 PM   #20
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Quote:
Originally Posted by EeePee View Post
I'm curious if the voltage did the damage.
I highly doubt it. I've been running two 7950's at 8.4 for a year and a half, and a 7980 at 8.4 for a year with zero issues (other than bent linkages).
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